Exterior siding and window jambs: sealant or backer rod and sealant?
We were reviewing some details in our office the other day and I noticed we had been showing backer rod and sealant between a “flanged” window and siding/trim. It get me thinking about all the articles I have seen in JLC, FHB, etc and never recall seeing the backer rod. Even Martin’s recent details in FHB don’t show it. Then I checked several window manufacturers and Andersen was the only one I found so far that says backer rod and sealant. Of course, they do say to leave 1/4″ gap, which to my knowledge is the smallest backer rod available.
So, what is everyone doing? I typically see 1/8″ gaps with sealant only against siding (fiber-cement) and stucco. With a properly installed/flashed window, it really shouldn’t matter except to provide for expansive/contraction and additional air sealing. I would expect a good quality sealant ($5+ tube) to perform with an 1/8″ gap and no backer rod. Thanks.
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