Siding materials naturally expand and contract as temperatures change. This is a normal part of how siding performs, but if it isn’t accounted for during installation, it can lead to large gaps, buckling, or other issues over time.
One of the most common questions is whether this movement is a problem. If the seam is caulked, the movement will eventually crack the sealant. A better way to deal with this is to protect the seam with butt joint flashing behind the siding instead of caulking the joint. Leave a gap to allow for the siding to move naturally without compromising your moisture barrier.
Different siding products expand and contract at different rates, so it is important to look at manufacturer’s recommendations for spacing and flashing. James Hardie fiber cement products will differ from LP Smartside, both in expansion rates and in their recommended sizes for joint flashing.
In the end, siding expansion and contraction is normal, but it has to be planned for during installation. Following the manufacturer’s recommendations and using the right joint treatment can help the siding perform better, look cleaner, and last longer.
