Custom Building Envelope Sealing Gaskets, Weatherseals & Foam Closures

No, and no honest supplier will claim otherwise. ASTM E283 (air leakage) and ASTM E331 (water penetration) are measured on the tested assembly: the window, door, or curtain-wall specimen under a specified pressure difference. ASTM E2178 qualifies the air-barrier material of record for the wall, which is a sheet or liquid membrane, not the gasket.

What the seal carries is its own material documentation: cellular and dense-gasket classes (ASTM C509, C864, C1115), a UL 94 flame class where rated, the test methods behind its properties, and lot-code traceability.

It is one material in the assembly that earns the rating; H-O supplies the converted part and the paperwork, and the assembly designer owns the tested rating. [1]

The perimeter joint is a movement joint, not a static gap. It has to accommodate framing tolerance, differential movement between the unit and the wall, and the installation shim stack, while keeping the air-barrier line continuous from the wall membrane onto the frame. Compressible closed-cell foam sized to the real gap range does the sealing; the joint is designed around the joint's minimum and maximum, not its nominal.

Air and water performance at this joint is a property of the installed assembly, tested by designation (ASTM E283, E331), not of the foam. What happens inside the unit — the glazing pocket, the setting blocks, the sash weatherstrip — is on Window & Door Systems and Curtain Wall Glazing & Perimeter.

EPDM is the durable default: strong UV and ozone resistance (per ASTM D1149 on the TDS), a broad service-temperature band, good compression-set behavior, and lower material cost, which covers the majority of exposed exterior weatherseals. Step up to silicone when the temperature band is wider than EPDM's comfort zone, when a UL 94 flame class is required, or when the detail wants chemistry-matched compatibility with a structural silicone sealant.

Neoprene is a moderate middle for limited exposure. The one rule that does not bend: keep ozone-sensitive rubbers off any exposed line. [9]

The line is the frame. Parts that ship inside the fabricated unit — setting and anti-walk blocks, glazing tape, glazing-pocket gaskets, structural-glazing spacer tape, sash weatherstrip, weep baffles, mullion plugs and end dams — are specified on the fenestration pages, because their selection depends on the section detail and the unit's performance class.

Parts installed on site around the unit — the perimeter joint to the rough opening, panel joints and transitions, closures at rainscreen and roof interfaces, expansion joints and firestop — are specified here, because their selection depends on the joint's movement range and exposure.

H-O converts both sides and kits them together on one drawing package when a project needs it; the pages split so each decision is argued once. Setting-block specifics are on Curtain Wall Glazing & Perimeter. [6]

Decide by the job. A seal or weather barrier wants closed-cell foam (or dense solid), which blocks air and water: closed-cell EPDM, silicone sponge, PVC, or neoprene, with cellular classes per ASTM D1056 (rubber) or D1667 (PVC). A drainage baffle wants open-cell reticulated polyurethane, which lets a pressure-equalized cavity drain water at the weeps while resisting air and insect pass-through.

The common error is a closed-cell part in a weep path, which traps the water it was supposed to let out. State whether each part seals or drains, and the cellular form follows. [11]

Cut the continuity in, don't trim it in the field. The assembly's air-infiltration rating (ASTM E283) is earned in the lab, but it only holds in the building if the seal is unbroken at every corner, stack joint, and splice; a gasket trimmed short or gapped at a splice guarantees the rating will not be met even though the material is correct.

Die-cut, mitered, and taped corners and pre-cut splice geometry remove the field-cut variability, and a field water check (AAMA 501.2) catches the leaks that slip through before occupancy. Send the corner and splice conditions with the detail and they get cut to the drawing. [13]

Precompressed impregnated foam sealant tape is a self-expanding, impregnated polyurethane product supplied in reels; it is an extruded/impregnated item rather than a part, so it is not in H-O's converting scope. Where a joint uses that tape, H-O's parts are the gaskets, closures, and transition seals around it, plus the slit glazing and butyl bedding tapes we do convert. If your detail calls for the precompressed expanding tape itself, we can point you to it and supply the sealing components that complete the joint.

Pick the chemistry first. UV and atmospheric ozone attack the polymer of an exposed seal; ozone cracking under strain and UV hardening are the classic slow failures of the wrong exterior rubber. EPDM and silicone are the UV/ozone-durable chemistries; EPDM carries ozone-cracking data per ASTM D1149 and heat-aging per ASTM D573 on the TDS.

Note that ASTM D1149 is a QC and research method, not a purchase specification, because real outdoor exposure varies by site, so use it as a comparative durability indicator alongside the grade's service history.

Keep ozone-sensitive rubbers concealed. [9]

We help you pick a compatible chemistry, and the final compatibility call is confirmed with the sealant maker. A gasket incompatible with the wet-applied or structural sealant it contacts can stain the substrate, lose adhesion, or migrate plasticizer that hardens the part.

The safe moves: match chemistry where you can (silicone gasket with silicone sealant, especially in structural-sealant-glazing details per the ASTM C1401 guide), avoid migrating-plasticizer PVC at sealant interfaces, and confirm the specific pairing with the sealant manufacturer before the mockup.

Tell us which sealant the gasket contacts and we steer the material choice accordingly. [14]

Yes. Pressure-sensitive adhesive (PSA) backing, a release liner, kiss-cut pieces on a carrier, and pull tabs are all applied in-house as part of converting.

For an envelope seal, the adhesive is chosen for the substrate and the exposure (surface energy, temperature, weather); silicone gaskets generally take silicone-compatible adhesives, and any adhered exterior seal should be validated for the substrate, surface preparation, temperature, dwell, and pressure of the actual assembly. Tell us the substrate and how the part is installed, and we specify the adhesive and liner with the geometry.

Samples typically ship in 3–5 business days for common configurations on materials we keep on hand, and standard production runs ship about 2 weeks after drawing approval. Extruded gasket profiles are coordinated through a partner network on custom lead times (tooling adds weeks). MOQ varies by material and part; prototype quantities through full production runs are equally accepted.

Everything is made to order and to your drawing; H-O is a converter, not a stocking distributor of finished parts. Send the detail and the quantities and we quote the lead time with the material recommendation.