Caulking For Fiber Cement Siding

The specification to omit caulk at siding butt joints is for new installations and is discussed in detail by the manufacturer.

Caulking for fiber cement siding. Check the caulking specifications provided in the installation guide by the manufacturer for your specific siding product. Measure and cut to length the first piece of siding and nail it in place photo 7. So what i would tell you to do is to use a colored caulk to choose the caulk in the color of the siding. 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.

Fiber cement boards are caulked only when there is no metal flashing behind them. Do not caulk fiber cement butt joints edges. Trim boards wood windows. 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. 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. Flashing acts as a waterproofing layer for this type of siding and caulking will prevent the flashing from doing its job. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture.

Applying caulk to the butt joint is ineffective because the gap is not large enough to accommodate the sealant. But you are correct that it is very difficult to paint. Caulk is usually used with fiber cement siding to prevent water intrusion at the butt joints. It s got good adhesion and expands and contracts.

Install the next piece so its end butts lightly against the first photo 7 inset. 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. 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.