Caulking For Fiber Cement Siding

Trim boards wood windows.

Caulking for fiber cement siding.

Dap alex plus 12 pack 10 1 oz white paintable latex caulk. 2 house built before 2008 so has no flashing okay to caulk. And this way you don t have to worry about painting it and you could still have the qualities of expansion and contraction and adhesion so it ll stay put once you apply it. Do not caulk fiber cement butt joints edges.

Applying caulk to the butt joint is ineffective because the gap is not large enough to accommodate the sealant. When james hardie siding products butt into wood based materials a 1 8 gap will allow for expansion and contraction of the wood based product. Caulking around windows doors eaves and trim edges gives added insurance that leaks will not occur. Fiber cement boards are caulked only when there is no metal flashing behind them.

Many professionals like those at james hardie also agree that you should not use caulk on fiber cement siding unless there is no metal flashing underneath. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. We only caulk butt joints on cedar siding if previously caulked. So what i would tell you to do is to use a colored caulk to choose the caulk in the color of the siding.

However this detail may not be effective at sealing the ends allowing water to be absorbed and swell the board ends. 1 i chose this caulk because it has 25 flexibility compared to silicone based caulk. Fiber cement boards don t expand and contract much but leave a little room for expansion at the end joints and then fill the gap with caulk. Item 157140 model 11532.

The specification to omit caulk at siding butt joints is for new installations and is discussed in detail by the manufacturer.