Caulking Between Siding Boards

If the siding joint is so tight that the caulk only bridges the gap it may split.

Caulking between siding boards.

Sometimes known as acrylic latex caulk. 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. Fill in gaps between crown moulding and baseboards. Do not caulk between siding and any built in receiving channels located at or around windows.

Seal a door frame in place and seal the subfloor at the bottom of a door frame. 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. 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. Vertical trim gap caulking.

Bottom of siding boards should not be caulked water is meant to exit through the bottom of each board. Leave a 1 8 gap between the siding and the trim or other materials to allow for structural movement. Another critical place is where the siding butts together in the middle of the wall. Also where the siding meets corner boards and corner board joints.

These siding joints can be caulked successfully if the gap is wide enough for the caulk to get into the crack. James hardie recommends the use of caulks and sealants that remain permanently flexible. It needs to move and breathe. Use latex painter s caulk inside of doors and windows or to quickly fill cracks.

The siding expands and contracts with temperature and humidity. Think of a wood home as a living thing. 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. Caulking them is a mistake and the caulking is likely to fail prematurely.

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. Always caulk between the siding and the trim.