Custom Expansion & Movement Joint Seals
H-O Products die-cuts and converts the sealing materials that go into building, deck, and parking movement joints: precompressed impregnated polyurethane foam sealant tape, closed-cell EPDM, neoprene, and silicone sponge compression seals, closed-cell backer, and elastomeric foam closures, cut to your joint drawing so the part matches the designed movement capacity and stays watertight through thermal cycling.
Built for: facade and precast panel movement joints, plaza and pedestrian-deck expansion joints, parking-structure bay joints, floor and topping isolation joints, and the compressible sealing component of fire-rated building joints, specified by movement capacity as a percent of joint width (validated per ASTM C719 / ASTM E1399 and classed per ASTM C920), not by thickness. The mechanical metal joint cover, where one is used, is a separate scope.
To pick the seal for a building movement joint, work from the joint's movement, not its size. Directly weather-exposed facade joint: specify precompressed impregnated PU foam sealant tape (about ±25% movement, Class 25 per ASTM C719), sizing joint width to roughly 4× the anticipated movement.
Field-applied sealant joint: set the sealant with closed-cell PE backer (ASTM C1330 Type C) so it bonds two sides only in the correct depth-to-width ratio. Compression seals and closures: closed-cell EPDM is the ozone- and UV-durable exterior default.
The remaining zones and duties are mapped in the When-to-spec list on this page. Values are per the TDS on file.
Movement, by designation: ASTM C920 (elastomeric joint sealants; movement classes 12½/25/35/50/100⁄50) · ASTM C719 (adhesion/cohesion under cyclic movement, the Hockman cycle) · ASTM E1399 (cyclic movement and min/max joint widths of architectural joint systems). Sealant-joint design: ASTM C1330 (backer rod Types C/B/O) · ASTM C794 (adhesion-in-peel).
Material-level, per the maker TDS: ASTM D1056 (flexible cellular rubber, Type 2 closed-cell classes) · ASTM D395 (compression set) · UL 94 (flammability classes incl.
V-0 on the rated grades). Water: ASTM E331 (static water penetration). Fire, at the tested joint system: ASTM E1966 / UL 2079. Exposure class for impregnated tape: DIN 18542 (BG1 exposed / BG2 concealed; a European scheme with no ASTM equivalent).
- Exposed facade / precast joint: impregnated PU foam tape
- Field sealant depth + bond breaker: closed-cell PE backer (Type C)
- Exterior compression seal (default): closed-cell EPDM
- Widest temperature / flame class: silicone sponge / V-0 flame-resistant silicone sponge
- Oil / light bearing: neoprene / rebonded neoprene
- Fuel / oil exposure: fluorosilicone sponge
- Precision low-set closure: PORON® microcellular urethane
- Joint transition membrane / butyl: butyl poly-seal tape / sealing membranes
- Fire-rated joint: seal as a component of a listed ASTM E1966 / UL 2079 system
This guide is for building-envelope, facade, structural, and restoration engineers and the spec writers and glaziers who specify the sealing element of a movement joint: precompressed foam sealant tape, a closed-cell compression seal, a backer that shapes a field sealant, or a foam closure, for facade, deck, parking, floor, and fire-rated building joints. If you are sourcing the mechanical metal joint cover itself, that is a separate scope; this page is the and converted sealing material that goes with it.
Where are you in the spec process?
This page serves engineers who already know the seal they want and engineers still choosing one by movement, exposure, and chemistry. Pick the path that matches where you are; you don't have to read the rest.
Send a joint detail, get a quote
An impregnated PU foam tape size, a closed-cell EPDM or silicone compression seal, a backer diameter, or a foam closure on your joint drawing, with the movement and exposure you need.
Skip to the quote form →Choose the seal by movement and exposure
Six selection factors (movement capacity, compression set, exposure and chemistry, watertightness, fire duty, and joint geometry), a seal-selection checklist, and the material families with TDS-cited methods and by-designation standards language.
Start with selection factors →
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1Send joint detailUpload a DXF, STEP, or PDF joint detail, or describe the joint: nominal width, minimum and maximum, exposure, and any fire designation. A sample part works too.
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2Material reviewEngineering reviews the movement capacity, exposure, chemistry, and watertightness against the maker TDSs, and frames the standards language correctly: material classes (ASTM D1056, UL 94) by TDS, movement classes (ASTM C920 / C719) by designation, fire ratings with the tested joint system.
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3PrototypeSamples typically ship in 3–5 business days for common configurations on materials we keep on hand. Made-to-order; MOQ varies by material and part.
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4ProductionStandard production runs ship about 2 weeks after drawing approval, on flatbed die-cutting, slitting for tape and backer, and kitting for joint sets. Ongoing parts run with material traceability and lot-code TDS records.
Which movement joint are you sealing?
Application Zones
Six kinds of movement joint define this page: the facade and precast wall joints where the seal is directly weather-exposed; the plaza, deck, and parking joints that add live load and chemistry; the floor and topping joints where a backer shapes a field sealant; the curtain-wall and structural-glazing perimeter joints; the fire-rated building joints where the seal is one component of a tested system; and the roof and cladding transitions where foam closures finish the joint.
Click a tab to see the seal, the controlling properties, and the families H-O converts for that joint.
Facade & precast wall joints: the seal is the weather line
Exterior wall movement joints and precast panel-to-panel joints move every day and season, and the seal sits directly in the weather: UV, ozone, and driving rain. Precompressed impregnated polyurethane foam sealant tape is the exposed-joint workhorse: supplied compressed on a roll, it expands to fill the gap and carries about ±25% movement (Class 25, validated per ASTM C719), with joint width sized to roughly 4× the anticipated movement and the exposed duty captured by the DIN 18542 BG1 exposure class.
Where the detail calls for a closed-cell compression seal instead, EPDM sponge is the ozone- and UV-durable default, and silicone sponge steps in for the widest temperature range or a flame class. One rule governs the callout: specify the movement capacity as a percent of joint width, not the thickness.
Plaza, deck & parking joints: movement plus load and chemistry
Elevated decks, plazas over occupied space, and parking-structure bay joints add two demands to the movement problem: live and traffic load across the joint, and a harsh chemistry of de-icing salts and, in parking, fuel and oil drips. The sealing element and its edge closures are chosen by exposure.
EPDM closed-cell sponge covers the general weather and salt duty; neoprene and rebonded neoprene add light bearing and some oil resistance where the closure also carries load; and fluorosilicone sponge is the answer wherever fuel or oil contacts the seal, since commodity foams swell and soften in hydrocarbons.
On membrane-protected plaza and pedestrian decks over occupied space, watertightness of the joint is the whole point, so the seal is specified to the deck's water requirement. The traffic-bearing metal cover plate, where the design uses one, is a separate scope; H-O supplies the compressible seal and closures that work with it.
Floor & topping joints: backer shapes a field sealant
Interior slab-on-grade, topping, and floor isolation joints most often use a two-part system: a closed-cell backer sets the depth and geometry, and a field-applied elastomeric sealant carries the movement. The backer's job is precise and easy to get wrong. Closed-cell polyethylene backer rod (ASTM C1330 Type C) controls how deep the sealant sits, so the installer hits the correct depth-to-width ratio and a concave hourglass profile bonded on two sides only.
That two-sided bond is what lets the sealant stretch and compress freely; a sealant that also grabs the joint back (three-sided adhesion) tears at the first big movement. Where a compressible foam filler suits the joint instead of a gunned sealant, closed-cell EPDM, PVC foam, or a PORON® closure carries the duty. Match the backer diameter to the joint width, and let the sealant's movement class answer to the slab's movement.
Curtain-wall & structural-glazing perimeter joints
Where a glazed facade meets the structure, the perimeter is a movement joint with an air- and water-sealing job: the curtain wall and the building move independently, and the transition has to stay tight. Precompressed impregnated foam tape and closed-cell compression seals bridge that gap, sized to the perimeter movement and the exposure.
Watertightness of the assembly is demonstrated by test at the assembly level (ASTM E331 static water penetration is the reference method), so the seal is specified to the wall's water requirement, not the other way around.
The glazing itself, its structural silicone, and the framing gaskets are the subject of the roofing, cladding, and structural-glazing sibling page; this zone is the movement and air/water seal at the perimeter transition.
Fire-rated building joints: the seal is a component of a tested system
When a movement joint runs through a fire-rated floor or wall, head-of-wall, floor-to-floor, floor-to-wall, or wall-to-wall, it becomes part of a fire-resistive joint system. The critical honesty rule lives here: the fire-resistance rating belongs to the specific combination of materials as tested, the listed joint system, evaluated per ASTM E1966 or UL 2079 (which also cycles the joint per ASTM E1399 before the fire exposure).
A converted compressible seal is one component of that tested assembly; it is never itself "fire-rated." H-O supplies the converted sealing component and its material-level documentation (including UL 94 flame classes on the rated grades per TDS); the listed-system documentation for the tested joint sits with the system designer. Silicone sponge and the flame-retardant silicone grades are the usual sealing materials in these assemblies for their temperature and flame behavior.
Roof & cladding transitions: foam closures finish the joint
At roof and cladding movement transitions, the seal's job narrows to a weather closure: filling and sealing the profile where a roof or wall movement joint meets a curb, parapet, or panel edge. Die-cut closed-cell foam closures do this work, shaped to the profile they close. EPDM sponge is the exterior-durable default; silicone sponge covers the higher-temperature and flame-class transitions; and closed-cell PE and PVC foam closures fill the simpler geometric gaps.
The closure is specified to the profile and the exposure; where the transition is part of a mechanical roof expansion-joint cover, that cover is a separate scope, and H-O supplies the foam closure and compression seal that go with it. The roofing membrane and cladding detailing are the subject of the roofing sibling page.
Six decisions that drive your movement-joint seal spec
A movement-joint seal is a single-purpose part with one controlling property per decision. Miss one and the failure is rarely immediate: the seal relaxes and leaks a few winters later, a sealant tears at the first big movement, or a fire-rated joint stalls at review on a material that claimed a rating it cannot hold.
Materials carry classes; joint systems carry ratings. A cellular class (ASTM D1056), a compression-set number (ASTM D395), and a UL 94 flame class belong to a material grade per its TDS. A movement class (ASTM C920, validated per ASTM C719) and a fire-resistance rating (ASTM E1966 / UL 2079) belong to the tested joint or joint system.
Write material classes on the seal callout, cite movement and fire by designation, and never let a drawing imply a foam seal is "2-hour fire-rated": the seal is a component of a system that is.
Movement capacity is specified as a percent of joint width, not as a thickness. A Class 25 seal accommodates about ±25% of its nominal width, validated by the ASTM C719 Hockman cycle; sizing joint width to roughly 4× the anticipated movement is what leaves that capacity in reserve. The value is a material or system property from the TDS, read against the real total movement of the joint.
Read the six factors below in order. The first two set the movement and the recovery (capacity, compression set); the next two answer to the environment (exposure and chemistry, watertightness); the fifth handles fire duty; the last one closes the geometry. Every factor names its test method, because in a movement joint the documentation is part of the part.
Show all 6 selection factors tap to expand
Movement capacity: specify the percent of joint width, not the thickness
Rule — size the seal to the joint's total movement expressed as a percent of joint width, and check the number against a cyclic test, not a catalog thickness. A movement joint opens and closes with temperature, load, and creep, and the seal is chosen by its rated movement: precompressed impregnated foam tape commonly carries about ±25% (Class 25 per ASTM C719), and elastomeric sealants are classed 25, 50, or 100/50 per ASTM C920.
Architectural joint systems are cycled per ASTM E1399 to establish their min and max joint widths. Get the total anticipated movement and the nominal, minimum, and maximum joint widths onto the detail; the seal size and class fall out of those numbers, and joint width should be roughly 4× the movement for a precompressed tape. [1]
Compression set: the long-game number that decides whether the seal still seals
Rule — pick a low-compression-set material and size it mid-range so recovery is left after years of cycling. Every thermal and mechanical cycle leaves a compression seal a little less recovery; when its contact force falls below the seal threshold, the joint starts to leak, months or years later. Compression set is measured per ASTM D395 (constant deflection, Method B, is the usual one), and the material that holds recovery widest across temperature is silicone sponge.
State the service temperature range and the design life, and let them push the choice between an economical EPDM seal and a silicone seal that keeps its recovery hot and cold. [9]
Exposure and chemistry: pick the polymer for what touches the seal
Rule — choose the elastomer by exposure first, then optimize. Exterior joints see UV, ozone, and rain; parking decks add de-icing salts and fuel and oil; interior joints are milder. Closed-cell EPDM is the ozone- and UV-durable exterior default; neoprene adds some oil resistance and light bearing; fluorosilicone is the fuel-and-oil answer where commodity foams swell; and silicone covers the widest temperature range.
For directly weather-exposed tape, the DIN 18542 BG1 exposure class marks the UV-durable, fully-exposed duty (BG2 is concealed). Name the exposure and any chemical contact on the detail; the polymer follows from it. [7]
Watertightness: the seal answers to the assembly's water requirement
Rule — specify the seal to the wall or deck's water-penetration requirement, and remember watertightness is demonstrated at the assembly level. On a plaza deck over occupied space, or an exterior wall, keeping water out is the whole point of the joint, and the reference method is a static water-penetration test of the assembly (ASTM E331).
A precompressed tape's own testing and a compression seal's continuous contact both feed that assembly result, so the seal is sized and placed to hold water at the design pressure, and a field sealant needs its correct backer-shaped profile to do the same.
State the water requirement and the exposure, and let the seal be specified to it. [10]
Fire duty: cite the system rating by designation, class the material by TDS
Rule — where the joint runs through a fire-rated assembly, build to a listed joint system and never claim its rating for the seal. A fire-resistive joint is rated at the tested-assembly level (ASTM E1966 / UL 2079, with the joint cycled per ASTM E1399 first), so the rating belongs to the specific tested combination, not to any single material.
The converted seal carries its own material-level flame class (UL 94, per grade TDS) and is a documented component of the listed system. Name the required fire designation on the detail and confirm the listed system; the seal, usually a silicone or flame-retardant silicone sponge, is specified to that system. [5]
Joint geometry: backer, bond breaker, and the depth-to-width ratio
Rule — where a field sealant carries the movement, let a closed-cell backer set the depth and break the third-side bond. A gunned elastomeric sealant only moves freely if it bonds two sides of the joint and sits at the correct depth-to-width ratio in a concave hourglass profile. Closed-cell polyethylene backer rod (ASTM C1330 Type C) does both jobs: it controls the sealant depth and acts as the bond breaker that keeps the sealant off the joint back.
A sealant that grabs all three sides tears at the first large movement. Give the joint width so the backer diameter and the sealant depth can be set; the geometry is what makes the movement class real in the field. [6]
Joint movement & exposure → material selection → converted seal → production supply.
- 1Joint movement & widthTotal anticipated movement, and the nominal, minimum, and maximum joint widths.
- 2Set the movement classPick the class (ASTM C920 / C719) against the real movement; size joint width to ~4× movement for a tape.
- 3Choose material familyEPDM, silicone, neoprene, fluorosilicone, PU foam tape, or backer, by exposure, chemistry, and fire duty.
- 4Add adhesive / liner / profilePSA backing, release liner, backer diameter, or the closure profile the joint needs.
- 5Die-cut to drawingDie-cut, kiss-cut, or slit the seal, backer, or closure to the joint detail with sealed, accurate edges.
- 6Quote prototype or productionSample set for the joint, then a production run with lot-code TDS records and traceability.
Specification Tools
Two tools to take you from "we have a movement joint" to here is the sealing-material shortlist for the joint detail: a requirement-driven seal-selection builder that assembles the shortlist with what to send and the citation language, and a side-by-side comparison of every sealing family on this page.
1. Movement-joint seal selection builder
Check the conditions your joint carries. The builder assembles the matching sealing materials into a shortlist with the family, what to send with the joint detail, and the citation language (material classes per TDS; movement and fire by designation, the fire rating with the tested joint system). The default selection below is pre-built for a typical exposed facade joint; every family is also printed in the material reference section, so nothing here exists only behind a script.
Sealing-material shortlist: 2 families selected
Each checked condition adds its material below. The list is the starting shortlist for the engineering review, not a certification: material classes (ASTM D1056, D395, UL 94) come from the grade TDS, and movement and fire (ASTM C920 / C719; ASTM E1966 / UL 2079) are cited by designation with the fire rating belonging to the tested joint system.
- Exposed joint: precompressed impregnated PU foam sealant tapeSend: nominal / min / max joint width, total movement, exposure. Cite: ~±25% (Class 25 per ASTM C719); exposed duty per DIN 18542 BG1.
- Field sealant joint: closed-cell PE backer (bond breaker + depth)Send: joint width for backer diameter and sealant depth. Cite: ASTM C1330 Type C; the sealant carries the ASTM C920 movement class.
2. Side-by-side: movement-joint sealing family comparison
Every family called out on this page, with construction, the property that drives its selection, the standards its TDS or duty cites, and the joint it serves. Click a column header to sort. Click any material name to jump to its accordion entry.
| Material | Construction | Selection property | Standards on the TDS / by designation | Joint | |
|---|---|---|---|---|---|
| Precompressed tape & exterior seals | |||||
| Precompressed Impregnated PU Foam TapeImpregnated PU foam | Precompressed foam roll | Movement (~±25%, Class 25) | ASTM C719; DIN 18542 (BG1/BG2) | Facade / precast | |
| Closed-Cell Silicone Sponge (BISCO® HT/BF, RS-series FR, V-0 grades)Silicone sponge | Closed-cell silicone | Widest temperature + flame class | UL 94 V-0 (per TDS); D1056 / D395 | Exposed / fire-rated | |
| Closed-Cell EPDM SpongeEPDM sponge | Closed-cell EPDM | Ozone / UV durability (exterior default) | ASTM D1056; D395 | Facade / deck | |
| Deck, parking & bearing closures | |||||
| Neoprene + Rebonded NeopreneCR foam | Closed-cell / rebonded CR | Light bearing + some oil resistance | ASTM D1056 (e.g. 2A1) | Deck / parking | |
| Fluorosilicone SpongeFluorosilicone sponge | Closed-cell fluorosilicone | Fuel / oil resistance | Per maker TDS; D1056 methods | Parking deck | |
| Closed-Cell / XL Polyethylene BackerClosed-cell PE | Closed-cell PE rod / sheet | Bond breaker + depth control | ASTM C1330 Type C | Floor / sealant joints | |
| PORON® Microcellular UrethaneMicrocellular PU | Microcellular PU foam | Low compression set (precision closure) | ASTM D3574; D395 | Floor / precision | |
| PVC Foam + Butyl / Sealing MembranesPVC foam / butyl | Closed-cell PVC / butyl tape | Closure & transition sealing | ASTM D1056; C920 (sealant) | Closures / transitions | |
Skip ahead and request your engineering review now
If your joint detail already calls out a foam tape size, a compression-seal material, a backer diameter, or a closure profile, send it over for engineering review against the TDSs and the movement and fire standards language.
Movement-joint seal failures you can prevent at spec
A movement joint fails quietly first: a seal that relaxed a few winters ago, a sealant that tore at the first hot summer, a tape sized to the gap instead of the movement, a fire-rated joint that claimed a rating it never held. Five patterns cover most of what goes wrong, and each is a decision made before the first seal is cut.
In a movement joint, the paperwork is part of the part. A correct material with an undocumented class, or a drawing that claims a fire rating for a seal, costs more schedule at review than any cutting error. Cite material classes per TDS and movement and fire standards by designation.
Show all 5 failure modes tap to expand
1. Seal sized to the gap, and it tore or leaked at the design movement
Fix — specify the movement capacity as a percent of joint width and check it against the joint's real total movement, not a catalog thickness. A seal or tape chosen to fill the nominal gap, without checking its rated movement, loses contact (a compression seal) or tears and debonds (a sealant) when the joint reaches its designed opening.
Pick the movement class (ASTM C920, validated per ASTM C719; architectural joint systems cycled per ASTM E1399) against the total movement, and for a precompressed impregnated foam tape size the joint width to roughly 4× the anticipated movement so capacity is left in reserve.
Send the nominal, minimum, and maximum joint widths and the total movement, and the size and class fall out of them. [1]
2. Compression set: the seal relaxed and the joint started leaking years later
Fix — choose a low-compression-set material and size it mid-range so recovery is left after years of cycling. A compression seal picked without regard to set is watertight on day one and slowly loses contact force as thermal and mechanical cycles accumulate; when the force falls below the seal threshold, water gets in, long after the installer left. Compression set is measured per ASTM D395, and silicone sponge holds its recovery widest across temperature, which is why it wins the wide-range and long-life joints over an economical EPDM seal.
State the service temperature range and design life, and size the seal so it still has recovery to give at the end of it. [9]
3. Three-sided adhesion: the field sealant grabbed the joint back and tore
Fix — use a closed-cell backer as the bond breaker so the sealant bonds two sides only, in the correct depth-to-width ratio. A gunned elastomeric sealant can only stretch and compress if it bonds the two joint faces and is free of the joint back; a sealant that adheres to all three sides cannot accommodate movement and tears at the first large opening.
Closed-cell polyethylene backer rod (ASTM C1330 Type C) both sets the sealant depth for the correct hourglass profile and acts as the bond breaker that keeps the sealant off the back. Give the joint width so the backer diameter and the sealant depth can be set; the geometry is what makes the movement class real in the field.
4. The wrong polymer for the exposure, and it swelled, hardened, or chalked
Fix — choose the elastomer by what touches the seal, then optimize. A commodity foam used where fuel and oil drip (a parking-deck joint) swells and softens; a non-UV-durable tape used in full sun on a facade chalks and degrades; a seal picked on cost alone fails on the exposure the joint actually sees.
Closed-cell EPDM is the ozone- and UV-durable exterior default, neoprene adds oil resistance and light bearing, fluorosilicone answers fuel and oil, and silicone covers the widest temperature range; for exposed tape, the DIN 18542 BG1 class marks the fully-exposed, UV-durable duty.
Name the exposure and any chemical contact on the detail, and the polymer follows. [7]
5. A fire-rated joint that claimed a material rating instead of a system listing
Fix — build to a listed joint system and cite the fire rating by designation; never claim it for the seal. A drawing note calling a foam seal "2-hour fire-rated" stalls at review, because the fire-resistance rating belongs to the specific tested combination of materials, the listed joint system evaluated per ASTM E1966 or UL 2079 (with the joint cycled per ASTM E1399 first), not to any single component.
The converted seal carries its own material-level flame class (UL 94, per grade TDS) and is a documented component of that system, usually a silicone or flame-retardant silicone sponge. Name the required fire designation on the detail and confirm the listed system; the seal is specified to it. [5]
Material reference
Detailed notes for the sealing families referenced on this page: the precompressed tape and exterior seals (impregnated PU foam tape, closed-cell EPDM, silicone sponge), the deck and bearing set (neoprene and rebonded neoprene, fluorosilicone), and the backers and closures (closed-cell PE backer, PORON® microcellular urethane, PVC foam with butyl and sealing membranes).
Values are per the maker TDS on file for each grade with the method named; movement and fire standards are cited by designation only, with the fire rating belonging to the tested joint system.
H-O die-cuts, kiss-cuts, slits, and kits every family to the joint drawing.
Tip — send the joint's nominal, minimum, and maximum width and its total movement with the family you are considering; the movement class and the seal size follow from those numbers, whichever family you pick.
Precompressed Impregnated PU Foam Sealant TapeExposed facade & precast joints · ~±25% movement (Class 25 per ASTM C719) · exposed duty per DIN 18542 BG1
There is no single dedicated ASTM product spec for precompressed impregnated foam tape; it is qualified against a set of test methods (movement per ASTM C719, water penetration per ASTM E331) and the European DIN 18542 exposure classes. Specify the movement as a percent of joint width and the exposure duty; the TDS carries the rest.
Closed-Cell EPDM SpongeOzone- and UV-durable exterior compression seals & closures · ASTM D1056 class · set per ASTM D395
EPDM is the economical exterior track; move to silicone where temperature range or a flame class drives the choice. Specify the cellular class per ASTM D1056 and the compression set per ASTM D395 against the real closure force.
Closed-Cell Silicone Sponge (BISCO® HT/BF, RS-Series FR, V-0 grades)Widest-temperature seals & the flame-class grades · UL 94 V-0 per TDS · the fire-rated-joint sealing material
Cautious language is part of this material's spec in a fire-rated joint: the seal supports a design evaluated on the tested assembly per ASTM E1966 / UL 2079. H-O supplies the converted layer and its documentation; the system designer owns the fire evaluation.
Neoprene & Rebonded NeopreneDeck & bearing closures with some oil resistance · ASTM D1056 (e.g. 2A1, 2-5 psi CD)
Specify the cellular grade per ASTM D1056 and, for a bearing closure, the bearing area and load. Do not assume a given neoprene sponge is oil-resistant by name; the class on the TDS is what says so.
Fluorosilicone SpongeFuel- and oil-exposed parking-deck joint seals · methods per the maker TDS
Specify the fuel or oil exposure and the closure force; the fluorosilicone grade and its TDS carry the fluid-resistance data.
Closed-Cell / XL Polyethylene BackerBond breaker + sealant depth control · ASTM C1330 Type C
Match the backer diameter to the joint width for the correct sealant depth. The backer controls the geometry; the field sealant, not H-O's part, carries the ASTM C920 movement class.
PORON® Microcellular UrethanePrecision low-set closures · CFD per ASTM D3574 · set per ASTM D395
Specify the force window (kPa) and the gap, not just thickness. PORON® is the precision, low-set track; the compression-set number is what keeps the closure honest over the service life.
PVC Foam Closure + Butyl Poly-Seal & Sealing MembranesSimple closures & transition sealing · ASTM D1056 (foam) · C920 context (sealant)
Specify the closure profile and the transition detail; the foam and membrane are cut to it. Where a gunned sealant carries movement at the transition, its ASTM C920 class is the sealant's, and the membrane or tape supports it.
Movement-joint seals: engineer-grade FAQ
Eleven of the questions we hear most from facade, deck, and building-envelope teams. If your question isn't here, send a joint detail or call, engineering picks up.
Is the seal fire-rated, and how are fire-rated movement joints handled?
No single material is fire-rated, and no honest supplier will claim otherwise: a fire-resistance rating belongs to the tested joint system, the specific combination of materials evaluated per ASTM E1966 or UL 2079 (with the joint cycled per ASTM E1399 first). What a converted seal carries is its own material-level documentation: a UL 94 flame class on the rated grade TDS and lot-code traceability.
It supports a design evaluated to the fire standards and is a documented component of a listed system; H-O supplies the converted layer and its paperwork, and the system designer owns the fire evaluation. [5]
How is movement capacity specified for a building movement joint?
As a percent of joint width, not as a thickness. A seal accommodates a certain percentage of its nominal width in extension and compression: precompressed impregnated foam tape commonly carries about ±25% (Class 25), and elastomeric sealants are classed 25, 50, or 100/50 per ASTM C920. The number is validated by a cyclic test (ASTM C719, the Hockman cycle; architectural joint systems are cycled per ASTM E1399).
Specify the total anticipated movement and the nominal, minimum, and maximum joint widths, and size joint width to roughly 4× the movement for a precompressed tape. [1]
Precompressed foam tape or a field sealant with backer: which one?
Both are valid; the choice is about the joint and the install. Precompressed impregnated PU foam tape is a self-contained seal for exposed facade and precast joints: it expands to fill the gap, carries about ±25% movement, and needs no cure or tooling. A field-applied elastomeric sealant carries the movement class directly (25, 50, or 100/50 per ASTM C920) but only works with the correct geometry, which means a closed-cell backer (ASTM C1330 Type C) to set the depth and break the third-side bond.
Exposed, fast, no-cure joints lean to the tape; joints already detailed for a gunned sealant lean to sealant-plus-backer. [6]
What is backer rod, and why does it have to be closed-cell?
Backer rod is the compressible backing placed behind a field sealant. It does three jobs per ASTM C1330: it limits how deep the sealant sits (so the installer hits the correct depth-to-width ratio and a concave hourglass profile), it acts as a bond breaker so the sealant adheres to two sides only, and it blocks sealant from flowing through the joint.
The standard classifies it by cell structure: Type C is predominantly closed-cell, Type B is bi-cellular, and Type O is open-cell. Closed-cell (Type C) is specified where water absorption must be low and the backing must not wick moisture into the joint. [6]
EPDM, neoprene, or silicone for a movement-joint compression seal?
By exposure and temperature. Closed-cell EPDM is the ozone- and UV-durable exterior default, and the economical choice for weather-exposed facade, deck, and roof-transition seals. Neoprene adds some oil resistance and, in its high-density rebonded form, light load-bearing for closures that also carry load. Silicone sponge covers the widest temperature range (roughly -55 to +200 C on the HT-class grades) and holds its recovery hot and cold, which is why it wins long-life and flame-class joints, including the sealing layer of listed fire-rated joints.
Cellular classes are per ASTM D1056 and compression set per ASTM D395 on each grade's TDS. [7]
How do I size the joint width for a precompressed foam tape?
Start from the anticipated movement, then apply the sizing rule. A precompressed impregnated foam tape carries about ±25% of its nominal width, and the maker TDSs call for a joint width of roughly 4× the anticipated movement so the tape stays weathertight through the full opening and closing cycle.
Each tape size covers a working joint-width range, so once you have the joint's nominal, minimum, and maximum widths and its total movement, the tape size follows. Send those numbers with the detail and the exposure class, and H-O returns a manufacturable tape size and the TDS. [12]
What makes a movement joint watertight?
Continuous seal contact through the full movement range, demonstrated at the assembly level. A compression seal has to keep contact force above its seal threshold at the joint's maximum opening; a precompressed tape has to stay expanded against both faces; a field sealant has to hold its bond through movement. Watertightness of the wall or deck is shown by test of the assembly, with a static water-penetration method (ASTM E331) as the reference.
The seal is specified and sized to the assembly's water-penetration requirement and its exposure, and a field sealant needs its correct backer-shaped profile to reach it. [10]
Does H-O make the metal expansion-joint cover?
No. H-O and converts the sealing materials that go into a movement joint: precompressed foam tape, closed-cell compression seals, backer, and foam closures. The mechanical metal joint cover plate and any extruded gland or gasket profile are a separate scope; H-O does not extrude profiles or fabricate the metal covers in-house (those run through a partner network or a separate supplier). If your design uses a metal cover system, H-O supplies the compressible seal and closures that work with it, cut to your joint detail.
DIN 18542 BG1 and BG2: is there an ASTM equivalent?
DIN 18542 is a European standard for impregnated sealing tapes on outside wall joints; it classes tapes by exposure, with BG1 for the highest, directly weather-exposed, UV-resistant duty and BG2 for concealed installations. There is no direct ASTM equivalent to the BG classification, so a US spec typically qualifies the tape against a set of ASTM test methods instead (movement per ASTM C719, water penetration per ASTM E331, and material properties per the relevant methods).
When a project references BG1 or BG2, treat it as the exposure duty the tape must meet, and confirm the equivalent performance on the specific product TDS. [12]
How long will the seal last, and what is compression set?
Compression set is a rubber's failure to recover its thickness after being held compressed, measured per ASTM D395 (constant deflection, Method B, is the usual one). It is the property that decides seal service life: a seal with high set gradually loses contact force over years of thermal and mechanical cycling until it drops below the seal threshold and the joint leaks.
Silicone sponge holds recovery widest across temperature, so it lasts longest in wide-range and long-life joints; EPDM is the economical exterior choice at more moderate ranges. Size the seal mid-range so recovery is left, and state the service temperature range and design life so the material is chosen for it. [9]
What should I put on the joint detail so the quote comes back right the first time?
The joint's nominal, minimum, and maximum widths and its total anticipated movement; the exposure (interior, exterior, deck, parking) and any chemical contact (salts, fuel, oil); the service temperature range; whether it is a field sealant joint (needs a backer) or a self-contained seal; and any fire designation and the listed system it must match. Plus the profile or a drawing, adhesive and liner needs, and quantities for prototype and production.
"Recommend the seal" is a valid callout: that is what the engineering review is for. Material classes come per TDS; movement and fire are cited by designation.
Glossary: terms used on this page
Quick reference for the movement-joint, sealing, and material terminology used throughout. Each entry links to the relevant standard or test method where applicable.
Movement capacity (percent of joint width)
How much a seal can be extended and compressed from its nominal joint width, expressed as a percentage. It is the primary spec for a movement-joint seal, packaged as a movement class per ASTM C920 [1] and validated by cyclic test.
ASTM C719 (Hockman cycle)
The cyclic test that subjects an installed sealant joint to water immersion, extension and compression movement, and temperature change to detect adhesive or cohesive failure, per [2]. It is the method that substantiates a sealant's movement class.
ASTM C920 movement class
The classification of an elastomeric joint sealant by the percentage of movement it accommodates: Class 25 is ±25%, Class 50 is ±50%, and Class 100/50 is +100%/-50% (asymmetric), per ASTM C920 [1].
ASTM E1399 (architectural joint systems)
The test method for cyclic movement and for measuring the minimum and maximum joint widths of architectural joint systems, per [4]. It establishes the movement a joint system endures and is the cycling step that precedes a fire test.
Backer rod (ASTM C1330 Types C/B/O)
Cylindrical sealant backing that sets sealant depth, acts as a bond breaker, and blocks sealant flow, classified by cell structure per ASTM C1330 [6]: Type C closed-cell, Type B bi-cellular, Type O open-cell.
Bond breaker / three-sided adhesion
A bond breaker keeps a field sealant from adhering to the back of the joint so it bonds two sides only and can stretch freely. Three-sided adhesion, where the sealant also grabs the back, over-stresses the sealant and causes it to tear at movement.
ASTM D1056 (cellular rubber class)
The specification that classifies flexible cellular rubber by Type (1 open-cell, 2 closed-cell), Class (A-D by chemistry and oil resistance), and Grade (0-5 by 25% compression-deflection force), per ASTM D1056 [7].
Compression set (ASTM D395)
The permanent deformation a rubber retains after prolonged compression, measured per ASTM D395 [9]. Lower set means a seal keeps its contact force longer; it is the property that decides seal service life in a cycling joint.
Precompressed impregnated foam tape
Open-cell polyurethane foam impregnated with a polymer and supplied compressed on a roll; installed into a joint it expands to seal, carrying about ±25% movement and, on the exposed grades, UV durability captured by the DIN 18542 [12] BG1 exposure class.
DIN 18542 BG1 / BG2
The European exposure classification for impregnated sealing tapes on outside wall joints: BG1 for the highest, directly weather-exposed and UV-resistant duty, BG2 for concealed installations. There is no direct ASTM equivalent; see [12].
Fire-resistive joint system (ASTM E1966 / UL 2079)
The test methods that establish the fire-resistance rating of a building joint as a complete, tested assembly, per ASTM E1966 / UL 2079 [5]. The rating belongs to the tested joint system, not to any single component material.
Rating belongs to the tested joint system
The honesty rule for movement-joint claims: movement and fire ratings attach to the tested seal or joint system, not to its component materials. A converted material carries its own classes (ASTM D1056, D395, UL 94) and supports a listed design without inheriting its rating.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and maker technical data sheets cited throughout this page. Movement and fire standards are cited by designation: they evaluate seals and joint systems, and the fire rating belongs to the tested assembly. Standards editions current as of July 2026; verify against the publishing body before final spec. H-O materials are aligned to these standards through the source manufacturer's TDS, not independently certified by H-O unless explicitly stated on the quote.
[1] ASTM C920 (by designation)
Standard Specification for Elastomeric Joint Sealants. Classifies sealants by Type, Grade, Class, and Use, and defines the movement classes (12½, 25, 35, 50, 100/50) that state the percent of joint width a sealant accommodates. astm.org (C920)
[2] ASTM C719 (by designation)
Standard Test Method for Adhesion and Cohesion of Elastomeric Joint Sealants Under Cyclic Movement (Hockman Cycle). The cyclic water, movement, and temperature test that substantiates a sealant's movement class. astm.org (C719)
[3] ASTM C1330 (by designation)
Standard Specification for Cylindrical Sealant Backing for Use with Cold Liquid-Applied Sealants. Classifies backer rod by cell structure (Type C closed-cell, Type B bi-cellular, Type O open-cell) and defines its depth-control and bond-breaker functions. astm.org (C1330)
[4] ASTM E1399 / E1399M (by designation)
Standard Test Method for Cyclic Movement and Measuring the Minimum and Maximum Joint Widths of Architectural Joint Systems. Establishes the movement a joint system endures; the cycling step that precedes an E1966 / UL 2079 fire test. astm.org (E1399)
[5] ASTM E1966 & UL 2079 (by designation)
ASTM E1966, Standard Test Method for Fire-Resistive Joint Systems, and UL 2079, Tests for Fire Resistance of Building Joint Systems (virtually synonymous). Both establish the fire-resistance rating of a joint as a complete tested assembly; the rating belongs to the tested joint system, not a single material. astm.org (E1966)
[6] ASTM C1330 backer functions (by designation)
ASTM C1330, referenced for the backer-rod functions used throughout this page: limiting sealant depth, breaking the third-side bond, and blocking sealant flow, with Type C the closed-cell class. astm.org (C1330)
[7] ASTM D1056 (by designation)
Standard Specification for Flexible Cellular Materials, Sponge or Expanded Rubber. Classifies cellular rubber by Type (open/closed cell), Class (chemistry and oil resistance), and Grade (compression-deflection), the classification behind the EPDM, neoprene, and sponge grades on this page. astm.org (D1056)
[8] UL 94 (material flame class, by designation)
UL 94, Tests for Flammability of Plastic Materials for Parts in Devices and Appliances. The material-level flammability classification (including V-0) cited by designation for the rated silicone and flame-retardant grades per their TDSs; a material class, not a joint-system fire rating. shopulstandards.com (UL 94)
[9] ASTM D395 (by designation)
Standard Test Methods for Rubber Property, Compression Set. Measures a rubber's ability to recover thickness after prolonged compression (Method B, constant deflection, is the usual one); the property that decides seal service life. astm.org (D395)
[10] ASTM E331 (by designation)
Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference. The reference method behind the assembly-level watertightness a movement-joint seal is specified to. astm.org (E331)
[11] Rogers PORON® industrial microcellular urethane (maker TDS)
Rogers Corporation PORON® industrial microcellular urethane technical data (4701 / 4790 series): compression-force-deflection per ASTM D3574 and long-term compression-set resistance, the basis for the precision low-set closures on this page. rogerscorp.com (PORON industrial)
[12] DIN 18542 (by designation)
DIN 18542, Sealing of outside wall joints with impregnated sealing tapes made of cellular plastics. Defines the BG1 (directly weather-exposed, UV-resistant) and BG2 (concealed) exposure classes for precompressed impregnated foam sealant tape. European standard; no direct ASTM equivalent. din.de (DIN 18542)
[13] Rogers BISCO® silicone foam / sponge (maker TDS)
Rogers Corporation BISCO® silicone foam technical data (HT and BF series; flame-retardant grades): service range on the order of -55 C to +200 C and UL 94 V-0 on the rated grades, the basis for the wide-temperature and flame-class seals on this page. rogerscorp.com (BISCO silicones)
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O converts materials aligned to the methods cited; H-O does not certify systems or fire ratings. Lot-specific documentation available on request.
To review your movement-joint seal, send:
- Nominal joint width
- Minimum and maximum joint width
- Total anticipated movement
- Exposure (interior / exterior / deck / parking)
- Chemical contact (salts, fuel, oil)
- Service temperature range
- Field sealant joint or self-contained seal
- Any fire designation and listed system
- Joint profile or drawing
- Adhesive / liner requirements
- Prototype and annual volume
Get a movement-joint seal engineering quote
Send a joint detail, drawing, or spec. We typically respond within one business day with a sealing-material recommendation, prototype lead time, and TDS verification against your movement, exposure, watertightness, and standards language.
See also: related H-O application pages
Engineering content for the adjacent general-construction sub-applications and the parent hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Sibling sub-application
Building envelope sealing
The wider air, water, and weather sealing of the envelope: perimeter gaskets, foam seals, and the closures around the movement joints this page covers.
Read the page
Sibling sub-application
Roofing, cladding & structural glazing
The glazing setting blocks, structural-silicone backing, and cladding-transition seals that meet the curtain-wall perimeter movement joints on this page.
Read the page
Sibling sub-application
Fire, life-safety & smoke control
The firestop, fire-barrier, and smoke-seal material story behind the fire-rated building joints on this page, where the rating belongs to the tested system.
Read the page
Industry hub
General construction
The full general-construction application family: envelope sealing, movement joints, roofing and glazing, fire and life-safety, acoustic and equipment isolation, and thermal insulation.
Read the page
Material data & standards. All movement, temperature, compression, and cellular-class values on this page are taken from the source maker's technical data sheets with the method named (ASTM D1056, D395, D3574; UL 94 classes per the listed grade TDSs).
Movement and fire standards (ASTM C920, C719, E1399, E1966, UL 2079; DIN 18542 exposure classes) are cited by designation only: they evaluate seals and joint systems, the fire rating belongs to the tested assembly, and the materials on this page support designs evaluated to them.
H-O converts materials; H-O does not design joints, size structural movement, or certify systems or fire ratings, and does not independently certify materials against the standards unless explicitly stated on the quote. Verify against the maker TDS and your project's listed-system requirements.
Conversion scope. H-O and converts sheet, roll, and profile stock to the joint drawing in Winsted, Connecticut: die-cut and kiss-cut compression seals and closures, slit tape and backer, waterjet-cut thick sections, laminations, and kitted joint sets, with material traceability and lot-code TDS records.
H-O does not extrude profiles or fabricate the mechanical metal joint covers in-house; extruded profiles and metal covers are coordinated through a partner network or a separate supplier. Lead-time and MOQ details are in the process strip and the quote form above.