Steven L. Smith, Bellingham, WA Home Inspector (King of the House)


Reference For Realtors: ID of L-P Siding

 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

Steven L. Smith

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Comment balloon 2 commentsSteven L. Smith • January 01 2008 06:15PM


Hi Steve,

Just a short comment about LP siding.  You are right about the knot, until you get to third generation LP.  For some reason, they dropped the knot on the newer stuff.  That makes it a lot harder to tell the difference between LP and Weyerhaueser.  Generally, if the house is 96 or newer and has LP, it won't have the knot; or if it had a lot of siding replaced using LP after 96, those will also not have knots.

Posted by David Helm, Bellingham, Wa. Licensed Home Insp (Helm Home Inspections) over 12 years ago


I was refering to the innerseal siding, which is the one with the big class action lawsuit. According to LP, all of that had the knot. That is why the post stated that pre-1996 LP is more of a worry. Also, the Weyerhauser siding with the two knots that we see is hardboard (more like Masonite) than oriented strand board. They call it hardboard in the manufacturer's literature. It has many of the same problems as OSB, and is composition, but should not be lumped in as OSB.

Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) over 12 years ago