Caulking For Fiber Cement Siding

Item 157140 model 11532.

Caulking for fiber cement siding.

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. So what i would tell you to do is to use a colored caulk to choose the caulk in the color of the siding. 1 i chose this caulk because it has 25 flexibility compared to silicone based caulk. Dap alex plus 12 pack 10 1 oz white paintable latex caulk.

However this detail may not be effective at sealing the ends allowing water to be absorbed and swell the board ends. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints. 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. 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.

Do not caulk fiber cement butt joints edges. Trim boards wood windows. Caulking around windows doors eaves and trim edges gives added insurance that leaks will not occur. 2 house built before 2008 so has no flashing okay to caulk.

We only caulk butt joints on cedar siding if previously caulked. Applying caulk to the butt joint is ineffective because the gap is not large enough to accommodate the sealant. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture.

Fiber cement boards are caulked only when there is no metal flashing behind them.