I recently inspected a new construction home that had LP Smartside lap siding installed. This type of siding has specific installation methods that must be adhered to in order to prevent water damage, expansion and contraction issues, and to maintain its warranty. It was obvious from the start that the installer was not trained in this type of product or installation. I have found this to be very common with LP Smartside and James Hardie – Hardie Plank fiber cement products. So let’s review the issues.
The installation of LP and Hardie products is similar but not the same, so for the purpose of this article I will be concentrating on LP Smartside Specifically.
Nailing Patterns
As I walked around the home in the mud I realized that they had face nailed the siding. My first thought was “Why did they face nail the siding?”. One of the benefits to this siding is it is generally blind nailed so no fasteners show. As a matter of fact, when it is face nailed the fasteners must then be sealed with an approved sealant and painted. Face nailing of the siding is not required in 6″ and 8″ wide lap siding. Face nailing IS required for 9″ or greater wide siding.
The second item I noticed was that they had nailed all of the siding with wire brad nails from a finish nailer. The manufacturer specifies that the nails be: Hot-Dipped galvanized with a .270 inch head and a .113 inch diameter shank. Wire brad nails do not meet any of these requirements. LP has very specific nailing requirements such as:
- Nail Type
- Fasteners must penetrate each stud a minimum of 1 1/2 inches and be spaced not more than 16 inches on center
- Nails must not be over-driven or under-driven
Wall Penetrations
The second area I usually look at with LP siding is the wall penetration flashings such as window openings, door flashings, hose bibs, light fixtures, etc. At the top (header) there is required to be a 3/8 inch gap with an aluminum cap flashing to allow moisture to escape. Condensation can form behind the siding and must be able to escape. This area is not allowed to be caulked as that may trap moisture and lead to water damage to the siding. On this particular home they utilized vinyl J-channels which would likely hold water and lead to water wicking into the siding via capillary action. At window flashings the ends of the flashing must also incorporate 1 inch of caulk to prevent water from penetrating down the window jamb area, if this step is skipped water can get behind the siding leading to water damage.
One of the most important parts of the installation is maintaining proper clearances. Required minimum clearances are:
- 3/8 inch from all flashings – DO NOT caulk except into the corners
- 1 inch clearance from hard surfaces – Roof, Concrete, Deck, etc
- 6 inches from grade – Grass, Ground, or Gravel
Siding Installation Requirements
Siding installation requirements are also very specific to prevent damage from nailing patterns to touch up sealant.
- All siding butt joints must be at a framing member
- Maximum nail spacing is 16 inches on center
- 3/16 inch gap at window and door jambs and corners, gap must be caulked
- Fastening below windows and the last row beneath the eave shall face nailed at 8 inches on center
Butt joints also get special consideration vs other siding products. With LP Smartside there are 3 acceptable installations. The first method is gapping the joint, a 3/16 inch gap is required at each joint. The gap is then sealed with Class 25 sealant. If the ends of the siding are not factory sealed they should be sealed in the field prior to installation and caulking. The second method is with a metal H molding. If H moldings are used, the thickness of the web must be added to the minimum gap width. The third option is a metal flashing behind each butt joint that extends over the siding below. In my experience this is the most common and best butt joint detail if done correctly. The joint does not get caulked and does not require the H molding, but the ends of the siding must either be factory sealed or sealed in the field.
Flashings
One last item that was incorrect on my recent inspection was the distance from the base of the siding to the roof line. one inch clearance is required. On this particular installation they ran a vinyl J-Channel and tucked the base of the siding inside it. Water will likely be present in the channel and lead to water wicking into the siding over time. At the eave where a wall extends past the gutter or fascia, a kickout flashing is also required to adequately divert water away from the wall. The roof step details are very important to prevent water intrusion.
In Summary
I would say that a large majority of Fiber Cement siding installs I inspect are installed incorrectly. The product is a good product but its life expectancy is heavily dependent on the correct installation, attention to penetration details, and maintenance (just like most products). It seems to me that many contractors install it like they would install wood siding, and that is a no, no.
I have not heard what happened with this particular inspection, I advised my clients to have an LP certified contractor evaluate and repair the siding, which I am guessing would require removing and replace the siding completely. That’s a big expense for a product that is brand new.
So if you are buying a home, even a new one and are on the fence on whether or not to get a home inspection, this type of story is not necessarily that uncommon. A $450 inspection may save you tens of $1000’s in the long run.
As always, I hope you took some value from this post. If you have any home related topics you would like to learn more about, please send them to my email below.
Aaron M. Zuehlke is the owner and a Certified Master Inspector® at Zuehlke Inspection Service, LLC, a full-service home inspection company serving Southern Wisconsin. Specializing in Home inspection, Radon Testing, Mold Testing/inspection, Well Inspections/Well Water Testing, Residential Thermal Imaging, and Manufactured Home Foundation Certifications. He also manages several rental properties through Zuehlke Properties, LLC. He can be reached at Aaron@zuehlkeinspections.com.