Manufactured Siding and LP

Siding, manufactured from oriented strand board and other wood composites, have the advantage of being manufactured from relatively low cost wood and young trees, thus saving money and attempting at a more benign impact on the environment. Such siding products became more attractive as traditional wood siding decreased in quality and/or increases in cost. Unfortunately, most of the experience with such siding products have been poor. Most of these products have experienced moisture related problems.

Louisiana Pacific Corp. came out with an Inner-Seal Lap Siding (LP Siding). Masonite developed OmniWood, and a number of other companies launched other similar products. Of all of these products, LP is the best known, but for the wrong reasons. LP has been involved in a highly publicized legal action and has agreed to pay for some siding damage.

I actually don't think that LP siding is such a bad product, and I hope that one of these years, newer versions of these products will have fewer problems. However, as of now (fall of 2004) I have not seen the evidence that allows me to recommend such a product.

The key issues relating to the longevity of LP and other manufactured wood siding products seem to be as follows:

  1. A better formulation of the materials and the manufacturing process.
  2. Good quality installation and careful attention to manufacturers installation and maintenance instructions.
  3. Low interior moisture levels, good venting systems, wide roof overhangs and the proper control of vegetation next to the house.

One of the problems with this type of siding is the requirement that it must be installed with "hidden fasteners", and not "face nailed." Each piece of siding is nailed along the top edge of the board, the nails are then covered by the next layer of siding. This requirement is intended to prevent water entry into the core of the material. Failure to follow these instructions has contributed to many of the damaged siding installations.

This "hidden fastener" requirement makes partial replacement of LP type siding very difficult. When replacing wood lap siding, a damaged piece is carefully removed and a new piece installed. The new piece is then face nailed into place. With LP siding repairs, such face nailing needs to be minimized and carefully caulked, or the siding needs to be glued into place.

Methods to reduce additional de-lamination - Before doing anything, it is very important to find out what if any help is available from the siding manufacturer. Following all of the manufacturers maintenance guidelines may be required in order to keep any warrantee in force.If the siding shows some swelling or thin fissures at the bottom edge, it may be possible to reduce further damage by priming the siding with "Permenizer Plus" or a similar primer and then repainting. The primer and paint may be applied with a spray gun, but the bottom edge and any other areas of defects must be brushed.

LP Siding Maintenance

Some of the pre 1996 versions of the LP and similar siding products failed soon after installation. Later versions have lasted longer but as of the fall of 2004, I have yet to see such a product that stands up in our wet Pacific Northwest Climate. The most common conditions which seems to warrant some "preventative" maintenance and eventual replacement are: limited swelling and thin cracks along the bottom edge of the siding.

LP (Louisiana Pacific Co.) does not seem to have any official recommendations about the maintenance of such siding. However, some of the LP staff and other suggest the following:

  • quality caulking of any dimpled nail heads and other holes etc.
  • priming with Parker "Flex Bind", Pittsburgh "Permenizer Plus", or similar primer material. Note: brushing the primer into the bottom edge of the siding is a critical element of this work.

  • keeping vegetation, soil, roof drainage and sprinkler water off the siding.

    This type of maintenance work is unlikely to solve all of the problems with this type of siding or help with severely deteriorated material but it should prolong the life of the product.

    How long can the damaged siding be made to last? Will this maintenance work help? I don't know, and no one else will know until the siding fails completely. But if I had some slightly damaged LP siding on my home, I would invest in this type of maintenance work.