Caulking Between Siding Boards

Sometimes known as acrylic latex caulk.

Caulking between siding boards.

Use latex painter s caulk inside of doors and windows or to quickly fill cracks. Also where the siding meets corner boards and corner board joints. 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. The siding expands and contracts with temperature and humidity.

While paint does tend to somewhat glue these pieces together caulking them is never advised and can cause permanent damage. If the siding joint is so tight that the caulk only bridges the gap it may split. The hypothesis that if it is properly sealed with caulk no moisture will get behind the boards has not only been proven wrong by building scientists it s dangerous and could lead to problems such as sick building syndrome and mold. James hardie recommends the use of caulks and sealants that remain permanently flexible.

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. It needs to move and breathe. Do not caulk between siding and any built in receiving channels located at or around windows. Fill in gaps between crown moulding and baseboards.

Best for use with drywall wood and masonry. Think of a wood home as a living thing. Seal a door frame in place and seal the subfloor at the bottom of a door frame. Leave a 1 8 gap between the siding and the trim or other materials to allow for structural movement.

In my opinion caulking between the seams in any lapped siding either horizontal or vertical is not good practice but not just because of any potential vapor barrier effect. Another critical place is where the siding butts together in the middle of the wall. 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. Bottom of siding boards should not be caulked water is meant to exit through the bottom of each board.

Caulking them is a mistake and the caulking is likely to fail prematurely. These siding joints can be caulked successfully if the gap is wide enough for the caulk to get into the crack.