Caulking For Fiber Cement Siding

Measure and cut to length the first piece of siding and nail it in place photo 7.

Caulking for fiber cement siding.

Gap where the end meets the corner board photo 7 inset and make sure the other end lands on a stud line. 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. However this detail may not be effective at sealing the ends allowing water to be absorbed and swell the board ends. But you are correct that it is very difficult to paint.

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. Applying caulk to the butt joint is ineffective because the gap is not large enough to accommodate the sealant. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job.

Fiber cement boards are caulked only when there is no metal flashing behind them. It s got good adhesion and expands and contracts. Trim boards wood windows. Caulk is not to be installed in j channel f channel nor in fiber cement siding butt joints though it may have been applied later by a homeowner or maintenance contractor.

We only caulk butt joints on cedar siding if previously caulked. Check the caulking specifications provided in the installation guide by the manufacturer for your specific siding product. Install the next piece so its end butts lightly against the first photo 7 inset. What you want to use is a silicone caulk because it s the most permanent one.

The specification to omit caulk at siding butt joints is for new installations and is discussed in detail by the manufacturer. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture. So what i would tell you to do is to use a colored caulk to choose the caulk in the color of the siding. A mark parlee a general contractor in des moines iowa responds in my experience water that gets trapped against fiber cement sidingcan be absorbed by the material causing joints to swell and shrink during freeze thaw cycles.