Installation Video Series, Part 7: Pre-Finished Lap Siding

LP® SmartSide® products can be professionally prefinished before they get installed on the home. When handling prefinished products, you'll want to use caution so as not to damage the prefinished surfaces. You'll have a few preferred methods of butt joint treatment to choose from. These practices will help control water runoff and house wrap exposure to the sun. For a quick reference, watch our expert demonstrating this repair process.

How to Treat Expansion Joints

Let's discuss the three preferred ways to treat expansion joints when installing LP SmartSide prefinished Lap Siding.

• Caulking. The first and most common method would be to caulk the joints. When two pieces of lap siding are installed with the required 3/16″ spacing, you can simply caulk that spacing with an ASTM C920, Class 25 (or higher) sealant. It is required to achieve two points of contact per bead of sealant. This means just the right amount of sealant. It should be touching both pieces of lap but not fill the gap all the way back to the house wrap. Be sure to follow the sealant manufacturer's instructions to best avoid water intrusion.

• Pan flashing. The second preferred practice is achieved by using pan flashing behind the butt joints. In many cases, you will be able to color-match the pan flashing to match the prefinished LP SmartSide products. Begin by nailing the length of the lap siding but do not nail the ends. The ends that make up the butt joint should be both factory-painted ends and spaced a minimum of 3/16″. Before nailing the ends of the lap, slide the pan flashing into place so the butt joint lands at the middle of the flashing and the flashing overlaps the course below, then nail the ends of the lap into the stud. You will want to do this at every butt joint.

• Joint molding. The third preferred method of butt joint treatment for prefinished lap siding is by using a joint molding or H-clip. Fasten the length of the lap but do not fasten the ends of the boards. Install the lap with a space consistent with the joint molding manufacturer's instructions at the butt joint, then carefully slide the joint molding into place until the bottom is flush with the bottom of the siding. Once the joint molding is in place, fasten the ends of both lap boards to the stud.

For more detailed information on siding products from LP SmartSide and complete installation instructions, visit the  LP SmartSide Installation Video Series.