Caulking Cement Fiber Siding

The following information is adapted expanded a bit from certainteed corporations installation instructions for the company s fiber cement siding products as this is the most comprehensive guide we could find for caulking clearance instructions when installing fiber cement siding.

Caulking cement fiber siding.

Siding butt joint treatment. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. 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. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints.

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. Natural siding boards are designed to expand and contract with the elements and we do not want any adhesive to prevent their natural movement. Do not deliberately leave butt joint gaps in fiber cement lap siding and that they do not recommend caulking field cut butt joints in their board type fiber cement siding products. It s got good adhesion and expands and contracts.

We only caulk butt joints on cedar siding if previously caulked. Caulking around windows doors eaves and trim edges gives added insurance that leaks will not occur. However this detail may not be effective at sealing the ends allowing water to be absorbed and swell the board ends. Fiber cement boards are caulked only when there is no metal flashing behind them.

But you are correct that it is very difficult to paint. Both certainteed and jameshardie as of september 2008 have made clear that siding butt joint gaps should never be made that is. Big stretch acrylic latex caulking sealant by sashco. That is why we are showing you some other products for various surfaces along with our top pick.