It’s all the rage these days; fake stone siding (manufactured stone veneer) as an accent on the front of a house (or it can be the whole siding in some cases). You can give your home that mountain cabin look, right here in suburbia. Manufactured Stone Veneer Siding (or Adhered Concrete Masonry Veneer as it’s technically known) is a thin, man-made siding made to look like natural stones or rocks. It’s basically molded concrete that looks like real stones. It’s normally installed over wood framing, but when installed incorrectly, it will let water in next to your wood framing, trap it, and wreak havoc on the structure of the house. And so far, I’ve yet to see an install done correctly in Louisville KY (or anywhere for that matter.)
Manufactured Stone Veneer Moisture Problems
Around 2012 I was called in by a homeowner here in Louisville, KY to look at his 2-year-old custom built house. His wife had tried to hang curtain rods on the front wall and his drywall was too wet and mushy to hold a plastic wall anchor. They had no clue why things were wet. I was able to trace it down to the manufactured stone veneer siding on the front of the house. The builder had omitted all the important flashing details with the install. That day began a fight with his builder that would last 2 years. For that entire period, his dining room was blocked off and unusable because of the extensive wood rot and mold problems that came along with it. The result: Attorneys were hired and things got ugly. The builder eventually repaired all of the water damage, stripped all the manufactured stone off, and replaced it with real stone (they did not try to install ACMV again). The final repair cost was close to $80,000.00.
Moisture intrusion experts have made the connection between manufactured stone veneer and traditional stucco (stucco homes in Louisville, KY are very rare to find). When problems arise from a botched install, a house with manufactured stone veneer shows the same moisture related issues as a house with a botched stucco system. It leaks behind the cladding and the water gets trapped. Then the house rots. In fact, one of the brightest minds in the world of building science, Dr. Joseph Lstiburek refers to manufactured stone veneer as “lumpy stucco.” He has a great article about that here: Stucco Woes.
Most manufacturers of ACMV are members of the Masonry Veneer Manufacturers Association or MVMA, who are now under the NCMA (National Concrete Masonry Association). I know, enough with the acronyms already. The MVMA puts out an installation guide (download the guide here) that is considered the “end-all-be-all” of how-to installation guides when it comes to manufactured stone veneer siding. When I am performing home inspections in Louisville KY, I refer to that guide and its details to show my clients how things should be done. The problem is I have never seen a home that has manufactured stone installed as the guide says it should be. Most every detail is usually skipped, and we all know the devil is in the details.
Flashing Details Make or Break Manufactured Stone Veneer Siding Installation
When big problems pop up with a house, you can usually trace its origins to a bunch of small things that add up to the train wreck at hand. That seems to be the reoccurring theme with the manufactured stone installs I am seeing. The most frustrating part for me as a home inspector is that by the time I get to see the house, most of the critical steps that must be done are covered up by multiple layers, and I’m left only to guess at what is (or isn’t) underneath the surface. But if the install crew can’t get the small, simple things correct, how could I expect them to actually do the really important stuff under it all.
Anyone who’s ever spent any time on a job site knows the attitude of most construction workers today. In the many years I worked in the trades, one of the more popular things to hear was “Looks good from my house,” or “We ain’t building a piano.” That’s a creative way of saying they don’t care. They do not care if you have problems later on. If it’s good enough to get things cleared, and them paid, let it roll.
Water Will get behind your manufactured stone veneer
A wise man once told me that water and women can be lumped into the same category: They both always win. Never is that truer than when it comes to the manufactured stone (ACMV) installation on your home. Water will find a way in. I repeat water will find a way. It will seep in around the cracks, and it will be absorbed into the chunks on concrete. You didn’t think this stuff was waterproof, did you? It’s colored concrete. It absorbs the rainwater, the sprinkler water, melting snow, etc. What we must do as construction professionals is design and build a wall system that can control the water, and not let it reach the structural framing of the house. The moisture will get past the concrete veneer; it’s what happens next that is vital to the integrity of your house. Every type of siding (or cladding, if you will) needs to be able to drain the moisture that gets by it.
Take brick veneer for example. Building codes have required a 1″ gap (brick manufacturers recommend a 2″ gap, by the way) between the sheathing on a house and the back side of the brick. When the water gets absorbed by the brick (No, brick veneer is not waterproof either), that gap is there to make sure we don’t soak the wood framing behind it and gives that moisture a path to escape at the base of the wall via weep holes. Take a look at the detail below of a brick wall and you’ll see the drainage plane present. The air gap is the colored red area. This allows the moisture a path to escape.
Manufactured stone veneer is typically installed on top of the wood sheathing on a house, and doesn’t have an air gap since it’s adhered or “stuck/mounted” to the framing, and not resting on the foundation wall in front of it (like brick veneer). If you want a trouble-free install, you must create a path for moisture to drain and a place for it to escape at the base of the wall/window/door/etc. If you do not have an escape point, the moisture will simply build up and rot out the base of the structure. I’ve never seen a home with a weep screed (escape point) installed, and I look at new construction houses every week. The builders are simply are not installing them.
Check out the wall detail below. You can see I’ve highlighted the weep screed in red at the base of the wall. This small piece of flashing will allow any moisture that has built up behind the manufactured stone a place to drain and allow fresh air a place to get in to help dry things out.
Proper Installation of Manufactured Stone Veneer Siding
Hindsight is always 20/20, and now that the problems with manufactured stone are coming to the surface, we’re getting smarter about it from an engineering standpoint (but in the field, it’s still all screwed up). If you actually read the whole MVMA install guide (you did read it, right?) you’ll see at the end of the document there are alternative methods for building the ACMV wall system. These include a drainage mat or furring strips mounted to the sheathing of the wall. In doing so you’ll essentially create an air gap between the house and the concrete veneer. Sound familiar? Just like our age-old friend, Mr. Brick Veneer, that air gap will allow for moisture control and drainage to occur, without the risk of the moisture soaking into the wood structure of the home. Is anyone doing this you ask? Not here in Louisville, but I hope they start soon. It’s likely going to take a couple of really big lawsuits to get this ball rolling. The process does require more planning, work, and careful execution to pull off and make work.
Inspecting Your Home for Manufactured Stone Problems
In future posts, I’ll break down the most commonly found incorrect areas, and give you details on how they should have been installed. I’ll be sure to update this post as well, as I gather new info and images from the field. If you have this material on your home and have questions feel free to contact me. More than likely your home’s veneer was poorly installed. I hate to say it, but I’ve never inspected a house that had a proper install of manufactured stone. There are ways we can take minimally invasive moisture readings from the inside of the home to get a better idea of what type of damage may be occurring on your home. If you’d like more info on this, just give me a call and we can talk about it. I have and can travel for this type of work as well, so don’t think just because you are not in Louisville, KY I can’t help.
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