Caulking For Fiber Cement Siding

Do not caulk fiber cement butt joints edges.

Caulking for fiber cement siding.

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. Caulking around windows doors eaves and trim edges gives added insurance that leaks will not occur. We only caulk butt joints on cedar siding if previously caulked. Dap alex plus 12 pack 10 1 oz white paintable latex caulk.

So what i would tell you to do is to use a colored caulk to choose the caulk in the color of the siding. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. Trim boards wood windows. 1 i chose this caulk because it has 25 flexibility compared to silicone based caulk.

Fiber cement boards are caulked only when there is no metal flashing behind them. Applying caulk to the butt joint is ineffective because the gap is not large enough to accommodate the sealant. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture.

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. The specification to omit caulk at siding butt joints is for new installations and is discussed in detail by the manufacturer. However this detail may not be effective at sealing the ends allowing water to be absorbed and swell the board ends. Butt joints however should be nailed tightly together and should not be caulked.

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.