Caulking Fiber Cement Siding

Big stretch acrylic latex caulking sealant by sashco.

Caulking fiber cement siding.

2 house built before 2008 so has no flashing okay to caulk. Sealing caulking fiber cement siding. How were butt joints and end joints treated flashed caulked. 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. Butt joints however should be nailed tightly together and should not be caulked. It is never acceptable to leave a gap of any size at a butt end joint. 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.

Butt end joints should be installed with factory sealed or factory prefinished ends butted together in moderate contact. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. 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. Fiber cement boards are caulked only when there is no metal flashing behind them.

Caulking around windows doors eaves and trim edges gives added insurance that leaks will not occur. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture. Cut ends of fiber cement siding should have been sealed using 100 acrylic latex primer or paint certainteed or in some cases using an approved caulk wiped on the cut surface see our notes on hardieplank installation. Placing caulk over large portions of wood siding prohibits the natural movement of the wooden panels and can cause extensive damage to the exterior of your home.

Do not caulk fiber cement siding butt joints edges. We only caulk butt joints on cedar siding if previously caulked. 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. That is why we are showing you some other products for various surfaces along with our top pick.