In Plain English
Quick Answer
A material applied to joints and gaps to prevent water, air, or fire from passing through.
Definition
Definition
A sealant is a flexible or semi-rigid material used to seal joints, gaps, and penetrations in building assemblies against air, water, sound, fire, or thermal transfer. Sealants differ from caulks in that they are engineered for specific movement capability and substrate compatibility. Common types include silicone, polyurethane, polysulfide, and intumescent sealants. Joint design must account for movement range to prevent sealant failure.
Context
Why It Matters in Bidding
Sealant scope frequently falls into gaps between trades, leaving joints unbudgeted until a building envelope consultant or punch list catches them. Specifying the correct sealant for movement and substrate up front avoids costly callbacks and warranty disputes, and estimators must align the right product, primer, and backer rod to the joint design the architect detailed.
Example
Example
Reviewing the spec, an estimator notices the exterior expansion joints require a high-movement silicone with a specific backer rod, prices it as a dedicated weatherproofing line item, and flags it in the scope so the curtainwall and masonry subs do not both assume the other carries it.
See Also
Related Terms
FAQ
Questions Contractors Ask
What is the difference between caulk and sealant?
Caulk is generally a lower-cost, lower-movement filler for static gaps, while sealant is engineered for a rated movement capability and substrate compatibility, often a percentage of joint width. Using caulk where the spec requires sealant invites premature joint failure, water intrusion, and warranty rejection, so match the product to the joint movement.
Which trade is responsible for sealant in a bid?
It varies by joint location. Glazing subs typically seal curtainwall and storefront, masonry subs handle masonry control joints, and a dedicated caulking or waterproofing sub may cover the rest. Because responsibility is ambiguous, scope sealant explicitly in each bid package to prevent both gaps in coverage and double pricing.
Why do sealant joints fail and how do you avoid it in pricing?
Most failures trace to wrong joint geometry, missing primer or backer rod, incompatible substrates, or a product whose movement rating is too low. Pricing the specified system completely, including primer and backer rod, and confirming the joint width supports the movement, prevents callbacks that consume any savings from a cheaper sealant.
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