Understanding Hurricane Product Approvals - Why sealants are a CRITICAL FAILURE POINT.

I learned something new yesterday from an engineer colleague about unsupported storefront jambs (the typical installation method), joint size, and sealant stretch.

Your 10'-12' tall storefront jambs are going to deflect under wind load and cause your sealants to stretch. This product approval assumes you are using DOWSIL 790 which has extension/compression joint movement of +100/-50% and it is very unlikely your window subcontractor is using that product.

This product approval REQUIRES a 3/8" gap a 9' or above so that the sealant can stretch up to 3/8". If you only have 1/4" shim space or are using a sealant with a lower stretch rating that sealant WILL FAIL AND LEAK!!

Is your window subcontractor using the proper sealant? Are they using backer rod? Are they using anchored or unanchored jambs?

A fenestration engineer should be reviewing your shop drawings and ensuring your subcontractor is following the detail to the letter. The building inspector is generally only spot checking the product is anchored properly, do not rely on them to certify your sealants.

I help architects and builders select, specify, and detail luxury hurricane glazing systems without dealer and manufacturer bias.