Flashing Behind Hardie Board Siding

Joint flashing material must be durable waterproof material that does not react with cement based products.

Flashing behind hardie board siding.

Flashing behind butt joints is an effective low maintenance way to comply with building code and help protect against water intrusion. However some local building codes may require different size flashing. A common problem with cement board siding products and some other types of horizontal lap siding is that older installation guidelines called for caulking the joint instead of flashing the joint. Water which makes it s way behind the hardie siding should hit the flashing layer.

James hardie recommends 6 inch wide flashing that overlaps the course below by 1 inch. Remember one of the main hardie siding problems is water damage however it s also one of the easiest to prevent with proper installation. As you can see in the photo above we ve installed a piece of flashing behind each field butt joint in order to keep water and moisture from getting behind the siding. Flashing is a strip of metal usually aluminum about 8 inches long and bent at 90 degrees with each side at least 5 inches wide.

The flashing keeps water off the sheathing and drains water properly which prevents water damage. Bearskin joint flashing is a plastic sheet for use as a joint flashing behind every butt joint in the siding. The product is a proprietary plastic 20 year uv rated sheet 4 ml thick that is basically a six by twelve post it note. On a wall to be covered with wood cement board vinyl or metal.

One of those recommendations deals with properly flashing behind field butt joints. Some local building codes may require different size flashing. This is a 6 wide piece of weather resistive material to make sure that no water gets through. This has proven problematic over time as caulking the joint results in unsightly surface appearances due to the different textures as well as resulted in failure of the caulk joint and associated ongoing maintenance.

There are several products that can be used in this type of application.