Caulking Between Wood Siding

Fill in gaps between crown moulding and baseboards.

Caulking between wood siding.

Any contractor worth their salt knows that you never caulk anywhere where water may need to escape. 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. Bottom of siding boards should not be caulked water is meant to exit through the bottom of each board. Sometimes known as acrylic latex caulk.

Caulking on the exterior siding joints at the corner board if done carefully does not need to be smoothed with a finger. 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. Think of a wood home as a living thing. It needs to move and breathe.

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. Most other areas were caulk is necessary should be lightly smoothed with your finger. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. Matt is 100 correct.

While paint does tend to somewhat glue these pieces together caulking them is never advised and can cause permanent damage. In fact some manufacturers warranties are void if you do. The siding expands and contracts with temperature and humidity. Caulking them is a mistake and the caulking is likely to fail prematurely.

You never ever caulk the underside of lap siding. Seal a door frame in place and seal the subfloor at the bottom of a door frame.