Curtain Wall Glazing & Perimeter: Setting Blocks, Glazing Pads, Structural Glazing Tape & Perimeter Seals

Apply the GANA Glazing Manual practice: two blocks per lite at the quarter points, block length scaled to glass area at approximately 0.1″ per square foot (industry practice also applies a commonly quoted minimum length around 4″), width sized to the full glass thickness with the edge clearance the glazing design specifies, and hardness in the 80–90 Shore A band per ASTM C864 Option I.

The sizing helper on this page does the arithmetic; the system manual and the project spec govern, and heavy, laminated, or sloped lites get reviewed by the system engineer. [2]

ASTM C864 Option I accepts all three as dense elastomeric blocks in the 80–90 Shore A band, so the decision is compatibility and aging, not load capacity. Solid silicone is the conservative default beside silicone sealants and across temperature extremes; dense EPDM brings weathering headroom where the spec names it; dense neoprene carries the longest service history and remains common in legacy specs.

Whichever you choose, run the block-to-sealant pairing through the sealant maker's compatibility program (the ASTM C1087 framework) and keep the letter in the submittal. [1]

Not as a material substitution. In conventional SSG practice per ASTM C1401, the structural silicone is the engineered attachment and the tape is the spacer that sets joint bite and thickness and fixtures the lite during cure. Systems do exist in which a tape is the tested, engineered retention, but that is a system-level qualification by the system supplier and engineer of record, with project-specific testing, not something an accessory supplier can confer by swapping materials.

H-O supplies the AFTC structural glazing tape (SGB/SGG/SGW, 0.09″ class) for the spacer/fixturing duty and verified compatibility per ASTM C1087; the structural joint design stays with the engineer. [4]

C864 covers dense elastomeric compression seal gaskets, setting blocks, and spacers, the non-cellular parts that carry load or hold dimension, including the Option I setting blocks on this page. C509 covers cellular (sponge/foam) elastomeric preformed gaskets and sealing materials, the compressible parts that seal pressure plates, stack joints, and perimeters.

Practical rule: if the part carries dead load or sets a dimension, it is C864 territory and dense; if it seals by compressing across a moving joint, it is C509 territory and cellular, with the firmness class per ASTM D1056 matched to the closure force.

[7]

Through the sealant maker's compatibility program, which tests accessory-sealant pairings under the ASTM C1087 framework and issues project compatibility letters. Send the sealant package (structural and weather seals, by product) and the accessory list (blocks, spacer tape, gaskets, by material and grade) and request letters for the exact pairings; keep them in the submittal, and treat any accessory substitution as a re-verification event.

H-O reviews your sealant TDS with the RFQ and flags the pairings that historically need attention, plasticized materials and oil-extended compounds first. [5]

Start from the joint's movement range, not the material. The gasket must stay in compression at the open extreme and not over-compress at the closed extreme, which sets the working deflection and, through the ASTM D1056 class, the firmness grade.

Then chemistry by exposure: closed-cell EPDM foam (the RE-series blend) or solid 553/563 EPDM sheet where the joint takes a dense strip for general duty, closed-cell silicone sponge where joint temperatures swing hard or the program wants silicone throughout. Stack joints are access-never positions; qualify one grade, hold it, and verify with AAMA 501-series mockup testing. [8]

Anti-walk (side) blocks sit at the lite's vertical edges to keep it centered in the opening when the wall racks under wind, seismic drift, or thermal movement; without them the glass migrates sideways, contacts metal, and chips or stresses the edge. They are standard practice in seismic designs and tall lites, typically softer than setting blocks because they cushion rather than carry dead load.

Die-cut silicone is the usual choice, sized to the pocket with the system's specified clearance. State the system's drift design on the RFQ and the geometry follows.

The pressure-equalized cavity stops draining at the rate the design assumed. Water stands in the glazing pocket, finds secondary paths, and shows up as a "glazing leak" in ASTM E331 or AAMA 501 water testing, expensive to diagnose because the sealants are innocent. Choose the PPI grade for drainage (lower PPI drains faster) and let baffle depth do the insect and reverse-flow exclusion; the baffle to the weep geometry rather than stuffing stock foam, and keep it on the BOM as a controlled part. [9]

Yes, as part of the tested assembly. Impact and cyclic-pressure qualification per ASTM E1886/E1996 certifies a specific material stack, glass build, retention, blocks, gaskets, tapes, and substituting an accessory after testing re-opens the qualification. Specify accessories by material, grade, and dimension in the tested configuration, and treat any change as an engineering event. H-O lot-codes converted parts so the accessory in the box is traceable to the TDS the test file references. [10]

Yes, that is the core service. Send the extrusion section or shop drawing and H-O gaskets, blocks, pads, baffles, and dams matched to the profile geometry: corner-matched gasket sets, keyed and notched setting blocks, kiss-cut-on-liner parts for the glazing line, and multi-layer laminations where a joint wants two materials in one part. We convert roll, sheet, and bun stock; extruded bulb profiles themselves come through a partner network while H-O converts the accessory set around them.

Usually, yes. Send the system manual's accessory pages, the incumbent TDS, or physical samples, and engineering cross-references to families H-O converts, matching on the spec-relevant properties: dense versus cellular class (C864 vs C509), durometer band, D1056 firmness class, chemistry, and the compatibility posture against your sealant package.

The result is an engineering cross-reference verified against the vendor TDS before quoting, with re-qualification risk called out where the system manual or a tested assembly names a specific accessory. Second-source qualification for glazing accessories is a common engagement.

No. H-O is a converter: we supply the converted accessories, blocks, pads, tapes, gaskets, baffles, dams, and the documentation that travels with them. The wet sealants come from the sealant makers, and the structural joint design belongs to the system engineer per ASTM C1401 practice. What we add on the sealant side is the compatibility review: send the sealant package with the RFQ and we check the accessory pairings against the TDS and flag what needs a C1087-framework letter before submittal.

Every curtain wall accessory is made-to-order to your drawing, including samples and prototypes. We keep common block, gasket, and baffle materials on hand for faster turnaround.

Samples typically ship in 3–5 business days for common configurations on materials we keep on hand. Standard production runs ship about 2 weeks after drawing approval, including kiss-cut-on-liner and corner-matched configurations. Expedited service is available when a mockup date is closing in. MOQ varies by material and part. Send the drawing and quantity through the form below for a specific lead-time commitment with your quote.