Problems with LP SmartSide® installations

LP SmartSide® is the new high-end siding of choice here in Minnesota.  It used to be stucco, but moisture intrusion problems with stucco siding made many high-end home builders start using James Hardie siding.  In the last few years, this his changed.  Today, I rarely see James Hardie siding used on new homes any more; builders are using LP SmartSide® instead.

For a head-to-head comparison, click on the following link for an in-depth discussion of James Hardie siding vs. LP Smartside, which Ryan Carey posted on this blog over a year ago.

LP SmartSide® is a great product that I have yet to find a single failure on, but I suspect I'll be seeing failures soon enough, because I find installation errors on nearly every home I inspect.  If you install LP SmartSide®, don't make these mistakes.  If you're buying a home with LP SmartSide® or you're having it put on your own house, watch out for these mistakes.  If you're a home inspector… well, you see where I'm going with this.  Check this stuff.  These are the most common mistakes being made by installers today.

Missing Paint

Without a doubt, the most common installation error that I find with LP SmartSide® is missing paint at the cut edges.  The manufacturer requires all exposed surfaces to be primed and painted.

Unpainted cut edge

Unpainted edge above roof

Unpainted edge above window

Overdriven Nails

This is another common defect.  Here's a small collage of overdriven nails.

Overdriven Nails

The diagram below shows the appropriate repair methods for overdriven nails.

LP Smartside Nailing Diagram

Insufficient Clearance

The manufacturer requires 6" of clearance from the siding to the finished grade.  It seems that almost every home has one or two areas where this clearance requirement isn't met.

Lacks required clearance to grade

The manufacturer also requires 1" clearance to shingles.  This is usually done right, but not always.

Lacks required clearance to shingles

The manufacturer requires a 3/8" gap above windows and other similar penetrations.

LP Smartside Diagram Clearance above window

This is rarely done.

Improper clearance above window

A 3/8" gap is a BIG gap.  Even when a gap is left here, it's usually not what the manufacturer requires.

Improper clearance above window 2

Improper butt joints

The manufacturer requires a 3/16" gap at the end of each piece of siding.  This includes butt joints, and places where the siding terminates vertically against windows, doors, and other fixtures.

LP Smartside gap at inside corner

Lacks gap at siding end

Improper gap at butt joint

A 3/16" gap is a pretty large gap.  Here's what a proper 3/16" gap looks like:

Proper gap at butt joint

Insufficient kickout flashing

Kickout flashing is a piece of metal at a roof end that prevents water from leaking into the wall.  See below.

Kickout Flashing

LP SmartSide® requires flashing to have a 4" upper leg.  This means the kickout flashing needs to be 4" high.  This usually isn't done.

Kickout flashing too short

Joint Treatments

There are three options for keeping water out of the butt joints.  The first and second options are to have the joints caulked or have joint molding installed.

Butt Joint Treatments

The third option is to have flashing at least 4" wide installed at the joints, as long as the ends of the siding are factory finished, and the siding is prefinished by an approved or preferred prefinisher.  That means no cut edges at the butt joints.  When field-cut edges are present, flashing at the joints is not an appropriate installation method.


That wraps up my list of the most common installation defects for LP SmartSide®.  Again, this is not a full list of defects.  For the full list of installation instructions, and for more information on this product, click here:   Why does this stuff matter?  Because if the product fails as a result of an improper installation, the manufacturer will not cover repairs.

Related Posts: 

Author: Reuben SaltzmanStructure Tech Home Inspections



Written By

Reuben is a second-generation home inspector with a passion for his work. He grew up remodeling homes and learning about carpentry since he was old enough to hold a hammer. Reuben grew up thinking he was going to be a school teacher because he enjoyed teaching others so much. In a sense, that’s a lot of what home inspections are about, so Reuben truly does what he loves. Sharlene has worked with Structure Tech since 2000 and Reuben has been contributing to her blog since 2008.

Related Posts

Siding Replacement Wars: James Hardie vs. LP SmartSide in a Battle for Contractors, Builders, and You

The current battle of paintable composite siding boards has given rise to quite the rivalry between LP SmartSide and James Hardie... the front line of this battle is taking place...

Photos from New Construction Home Inspections, Part II

Just like the orthodontist will tell you your kid needs braces, the home inspector is going to say you need a home inspection. I get it. That's why I try...

Subscribe to Our Newsletter for Market Updates & Mid-Century Modern Listings

Our weekly HomesMSP Update includes current local market information and a curated list of mid-century modern properties for sale, plus posts from an inspector, a lender, a stager, info about neighborhoods, life in the Twin Cities… even recipes!


Blog Categories


Sharon and John Hensrud

About Us

The HomesMSP Team is committed to meeting you where you are and listening… really listening to understand you so we can use our extensive knowledge of the market and local neighborhoods to give you personalized service.