Caulking For Fiber Cement Siding

Trim boards wood windows.

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. 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. We only caulk butt joints on cedar siding if previously caulked.

Butt joints however should be nailed tightly together and should not be caulked. The specification to omit caulk at siding butt joints is for new installations and is discussed in detail by the manufacturer. So what i would tell you to do is to use a colored caulk to choose the caulk in the color of the siding. Item 157140 model 11532.

Fiber cement boards are caulked only when there is no metal flashing behind them. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture. 2 house built before 2008 so has no flashing okay to caulk. 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. 1 i chose this caulk because it has 25 flexibility compared to silicone based caulk. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints. Caulking around windows doors eaves and trim edges gives added insurance that leaks will not occur.

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