I have posted about this before, probably almost a year ago, but the issue comes up enough that I think it is worth spending some time on it again. If you are a real estate professional, you might want to save this for easy reference. Realtors, often the seller's realtor, have to deal wit the home inspection and a home inspector called out that the home had Louisiana Pacific (L-P) innerseal siding. If the siding is composition wood and the home was built from the early 1980's until 1995 or even later into the 1990's in some cases, then that is certainly possible if the inspector got it right. Some inspectors are better at identifying these products than others. In my region, the Pacific Northwest, L-P was the most common of the composition sidings (oriented strand board or hardboard) and they are basically ground wood fibers, or wood wafers, and resins.
Realtors need to know that Masonite and Weyerhaeuser brand composition wood sidings are not uncommon and these products had similar problems, and their own class action lawsuits, as did L-P. Bottom line: The word L-P siding might scare people and the buyers more but, if the siding is not L-P but another brand of a similar material and vintage, you are probably still faced with the same issues if the siding has problems.
Regardless of this fact, that other sidings can be just as problematic, when the term L-P comes up, the biggest issue involves the older innerseal siding. While many of us are not exactly sold on the new composition wood sidings, the products that receive the most attention are those that were installed pre-1996.
Below, for your study and future reference, are photos to help you easily identify L-P innerseal for yourself -- to confirm if the inspector was right or wrong. The L-P innerseal siding came in both panels and lap siding with a signature knot. Often there are coats of paint over the knot, so it might be a bit hard to make it out and it might look a bit funny if you highlight it, if you get off the indentations. However, with a little effort you can see the shape of the knot, especially if you take a pencil to highlight the indentations, as shown below.
Note: You might really need to look all over the house to find any knots. In other words, if you do not see a knot on one side, keep looking before you give it up. Often the lap siding was cut so the knot was chopped off many boards when they were cut to length. Sometimes I find the knot right away but other times I have had trouble finding the knots and then, suddenly, found several of them in one area -- like pieces of board that were cut and used in that area because they fit there. FYI: The Weyerhauser siding also has a couple possible knot patterns, but we will deal with those in another blog. Right now, let's focus on L-P innerseal siding and what the knot will look like.
Factory supplied photo of the knot Red arrow is the L, Blue arrow is the P
L-P knot on a panel, not lap siding View of the wafers below, oriented strand board
Thanks for looking.
Steven L. Smith
Bellingham WA Home Inspector