Caulking For Fiber Cement Siding

Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture.

Caulking for fiber cement siding.

Do not caulk fiber cement butt joints edges. However this detail may not be effective at sealing the ends allowing water to be absorbed and swell the board ends. Applying caulk to the butt joint is ineffective because the gap is not large enough to accommodate the sealant. Butt joints however should be nailed tightly together and should not be caulked.

1 i chose this caulk because it has 25 flexibility compared to silicone based caulk. Trim boards wood windows. We only caulk butt joints on cedar siding if previously caulked. The specification to omit caulk at siding butt joints is for new installations and is discussed in detail by the manufacturer.

Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. 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. 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. 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.

Item 157140 model 11532. 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. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints.

Dap alex plus 12 pack 10 1 oz white paintable latex caulk.