Impact, Blast & Acoustic Glazing Components: Anti-Walk Blocks, Retention Gaskets, Energy-Spreading Cushions & Acoustic Layers

Anti-walk blocks are dense elastomeric blocks placed in the glazing pocket to stop the lite migrating out of position. Under the pressure reversals of a cyclic-loading sequence, and under the in-plane racking a drift design allows, an unrestrained lite creeps a fraction at a time until the edge clearance is gone on one side and doubled on the other; once the glass edge finds metal, the bite geometry the test report qualified no longer exists there.

Specify them wherever the assembly sees cyclic pressure, wind reversal or drift. Dense silicone, EPDM or neoprene per ASTM C864 Option I is the usual material, with impact-duty durometer typically at the upper end of the 80–90 Shore A band and a keyed geometry so the block engages the pocket rather than relying on friction.

They do two different jobs. A setting block carries the lite's dead load to the frame: a steady, one-directional load, sized by glass area, placed two per lite at the quarter points. An anti-walk block resists an alternating in-plane load that reverses thousands of times through a cyclic-pressure sequence and again under drift and thermal movement. The first job rewards a block that does not creep under sustained compression; the second rewards a block that does not indent or take a set under repeated reversal and that keys positively into the pocket.

Setting-block sizing lives on the Curtain Wall Glazing & Perimeter page; this page owns retention.

Not as a purchasing decision. A Notice of Acceptance is issued to a configuration, and that configuration names the accessories by material, grade, durometer and dimension. Changing a block from 85 Shore A to 70 Shore A is a change to the tested configuration even though both are the same chemistry and both read as silicone blocks on a purchase order.

The building would then carry a configuration nobody tested. Treat every accessory inside an approved assembly as a controlled item, lot-coded to its technical data sheet, and route any change through the approval holder as an engineering event.

No. Impact, blast and acoustic performance belongs to tested assemblies, not to components. An ASTM E1886 result against the E1996 specification, an ASTM F1642 airblast qualification, a Florida Building Code HVHZ approval or Miami-Dade Notice of Acceptance, and an ASTM E413 STC classification are each issued to a specific configuration of frame, glazing build, retention method and accessories.

H-O supplies converted parts to that configuration and provides the material documentation that travels with them; H-O does not confer, extend or certify an assembly rating, and no data line on a material technical data sheet is an assembly rating.

They work as a pair. ASTM E1886 is the test method: a missile is propelled at the specimen, and the impacted specimen is then taken through a sequence of cyclic static air-pressure differentials in both the positive and negative directions. ASTM E1996 is the performance specification that decides which missile, which wind zone and which pressure-cycle sequence apply to a given building and exposure.

They are the Testing Application Standards used in Florida's High-Velocity Hurricane Zone. TAS 201 is the large missile impact test, TAS 203 is the cyclic wind pressure loading test that follows it, and TAS 202 is the uniform static air pressure test for structural performance.

Because elastomers and microcellular foams are viscoelastic, so their stiffness depends on how fast they are loaded. A compression force-deflection curve on a technical data sheet is measured at the slow, standardised crosshead speed the test method specifies; a blast or missile-impact event delivers its load in milliseconds.

At that rate the same cushion can be several times stiffer than the curve suggests, which turns a layer meant to absorb energy over a stroke into a nearly rigid spacer that reaches full compression early and passes the remaining load through to the bite line.

Use quasi-static data for shortlisting, keep the thickness the tested stack used because stroke is part of the mechanism, and let the assembly test settle the stack.

Microcellular polyurethane is the usual answer, with the PORON® industrial 4701–4790 family the common specification. Its very fine cell structure gives a long, progressive compression curve, so the layer spreads a short, high-amplitude load into a longer, lower-amplitude one instead of transmitting it as a spike.

Compression force deflection, compression set and density are characterised per ASTM D3574 lines on the published technical data sheet. High-resilience natural rubber such as the BLAST-139 grade serves the retention gasket positions alongside it.

Mullion end dams are die-cut closures that seal the open end of a mullion or horizontal cavity so water reaching that cavity is routed to the weep instead of running out into the wall. Closed-cell crosslinked polyethylene is the usual media; pair the dam with a reticulated polyurethane baffle so the weep drains rather than stands.

Almost always because of flanking, not because of the glass. Transmission loss through parallel paths is governed by the weakest path, so a handful of small openings can pull a field measurement far below the laboratory classification the specification quoted. The usual offenders are an unbaffled mullion cavity that resonates and re-radiates, an unsealed perimeter at the slab edge, hardware and anchor penetrations, and any air gap the seal design missed.

The countermeasures are cavity absorption in the resonant voids, a mass-loaded barrier layer where the cavity cannot be deepened, and die-cut closures on every flanking path, each listed as a controlled part on the bill of materials.

They solve different halves of the problem. An absorber is open and light: it dissipates sound energy inside a cavity so the cavity stops amplifying and re-radiating, and its performance is characterised as a sound absorption coefficient measured per ASTM C423. A barrier is limp and dense: it raises transmission loss through the path it covers, and its lever is areal mass, which is why it is the answer when a cavity cannot be made any deeper.

Ultra-light polyimide foam such as SOLIMIDE® AC-530 and AC-550 serves the absorption role; mass-loaded silicone barrier such as BISCO® A2 serves the barrier role.

Start from the ageing mechanisms rather than the mechanical table. Coastal service adds ultraviolet exposure at exposed faces, chloride-laden moisture in every joint, and atmospheric ozone that attacks unsaturated rubber backbones under strain. Silicone and EPDM take that exposure without a special grade call-out; natural rubber and neoprene are more ozone-sensitive by chemistry and want a grade selected for it, with ozone resistance characterised per ASTM D1149 on the technical data sheet, such as the AMS 3208 weather-resistant neoprene grade.

Put the exposure on the RFQ beside the mechanical requirement, and remember that inside a tested configuration a grade change is still a configuration change.

Usually, yes, and the review starts from the document rather than the catalogue. Send the accessory pages of the test report or Notice of Acceptance, the incumbent technical data sheets, or physical samples, and engineering cross-references to families H-O converts, matching on dense versus cellular class, durometer band, cellular firmness class, chemistry and exposure grade, and thickness. The re-qualification consequence is called out on the quote wherever the RFQ would diverge from the configuration the document describes.

No. H-O is a converter: it die-cuts, slits, laminates and kits roll, sheet and bun stock into the accessory set — blocks, retention gaskets, cushions, dams, baffles, absorption and barrier layers — and supplies the documentation that travels with them.

Glass, interlayers and glazing units come from the glass fabricator; wet sealants and structural silicone come from the sealant makers; extruded profiles come from the system supplier; and the assembly design, the test programme and the approval belong to the system manufacturer and the engineer of record.

Every part on this page is made-to-order to your drawing, including samples and prototypes, and common block, gasket, cushion and baffle materials are kept on hand for faster turnaround.

Typical prototype lead time is 5–10 business days after drawing review, depending on material availability, tooling, and inspection requirements; parts can move in 24 hours when the material is already in-house. Standard production runs ship about 2 weeks after drawing approval, and expedited service is available when a test date or a mockup date is closing in. MOQ varies by material and part.