Louisiana-Pacific Inner Seal Siding

LP Inner Seal Siding

LP Inner Seal Siding - A brief history

Louisiana-Pacific Inner Seal siding, commonly referred to as “LP”, exploded onto the market in the early 1990’s. Forming from a Georgia Pacific spin-off in 1972, the Louisiana Pacific brand introduced itself into the market, expanding primarily through acquisitions; firmly establishing itself when the company bought the Fiberboard Corporation and fifteen southern California building centers that provided the needed distribution points for their operations.

Due to the death of the Southern Pine and Douglas Fir market for solid wood lumber production, in the late 1970’s the company began manufacturing Oriented Strand Board (OSB) by slicing logs into wafers mixed with resin and pressed into panels or sheets. First introduced as Wafer-Wood and later renamed as Inner Seal, the product revolutionized the lumber industry by offering a less expensive and stronger alternative to plywood sheathing.

Manufactured from early 1990 through 1996, LP Inner Seal siding was made from this process. As a note, OSB is widely used today as a substitute for plywood. If you watch modern houses being constructed, nearly all of the wall sheathing, sub-floor and roof decking is done using OSB. Louisiana-Pacific used this OSB material and formed it into siding panels and lap siding with an embossed covering meant to look like the natural grain in real wood.

LP, however, was not the only player. The 1990’s saw other “hardboard sidings,” or sidings made from a composite of wood fibers emerge onto the market. Weyerhaeuser had their product, so did Masonite. The other products could be accurately labeled as a hardboard siding, whereas LP’s Inner Seal is an OSB siding product. Technicalities set aside, the whole wood products industry was racing headlong into the composite wood siding business and nearly every one of these 1990’s era wood siding products had problems with premature failure and product defect litigation.

Identification and Problems. LP Class Action Lawsuit.

LP Siding Knot Identification
LP Siding Knot Identification

Louisiana-Pacific Inner Seal siding can be identified by the classic LP knot that is embossed into the siding, as depicted above.

The Inner seal product was sold as both a lap siding (most vulnerable) and in panel 4’x8’ sheets with the T1-11 profile (less vulnerable). With the lap siding, water is known to cling to the drip edge and wick into the bottom edge of the siding. Once water started to penetrate the drip edge, the siding saturated, swelled and delaminated. Once the product failed and swelled, the deterioration could not be reversed (by painting for instance) and required replacement. 

As a result of the defect, LP became a defendant in a major class action suit https://www.lieffcabraser.com/defect/louisiana-pacific-siding/ and paid claims for the product discoloring, disintegrating, and even microbial growth. Two years after the suit and after LP settled all related suits, the product was re-engineered and is now marketed as LP SmartSide http://www.lpcorp.com/smartside/lap/resources/. Since the 1997 re-engineering, the company has sold approximately three billion square feet with no warranty claims. 

As of today, the settlement for lawsuits associated with LP Inner Seal siding has been paid, and the opportunity to file a claim has passed. 

LP Siding Delamination
LP Siding Delamination

Useful life of LP Inner Seal Siding

The useful life of LP Inner Seal siding depends a great deal on the amount of exposure and the quality of the installation. The siding will perform adequately when it is protected by generous roof overhangs and is well-installed. However, it will tend to fail where exposed to the weather, and where sloppy installation leaves the product vulnerable. 

The T1-11 panel siding tends to do better than the lap siding because there is no drip edge for water to cling to.

One way to prolong the useful life of the siding is to keep it well-maintained. All penetrations, such as over-driven fasteners and site cut edges of siding need to be sealed with caulk and paint. A product commonly used to seal the drip edge is a paint primer called Permizer Plus; this can slow the delamination of the bottom drip edge. Lack of maintenance, exposure, and poor installation are common and major contributing factors to premature failure of LP Inner Seal siding.

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