ACMV Part 2- Trouble Areas Around Windows & Doors

Start Here to read the first post in this series. This will help you better understand the details for each section of the ACMV series.

If there is one constant when it comes to ACMV (Adhered Concrete Masonry Veneer), it is that you must be sure the moisture can drain from behind the siding. This drainage is achieved by incorporating a drainage plane & weep screed (a place for the water to drain to, and path for it to escape). When you look at all of the detailed diagrams on the subject, you’ll notice that every one of them has a drainage point where the siding meets another horizontal surface. This means that every window, door, trim piece, and the ground must have a drainage point to release the water that will get behind the siding.  If this detail is omitted, and it almost always is, moisture can build up and leak behind the moisture barriers that are in place.  Let’s look at some pictures to see what happens when things go wrong.

Window and Door Heading Detail

Below is a detailed diagram of what you should see when looking at ACMV manufactured stone install.  Notice the weep screed at the top of the window to give the moisture a place to drain, and an expansion gap (with backer rod and sealant to keep wind-driven rain out). When that flashing is missing (and it almost always is), the water that gets behind the stone will collect and build up on top of the window (the head).  I’ve added some rain drops to the image to help you better understand what happens to the moisture, and what path the water takes as the wall takes on wind-driven rain.

ACMV Window-Head-Detail

Here is a colored detail of what the top of a window or door should look like when looking at an ACMV install.


Now let’s look at a picture from an inspection of a typical ACMV install I see in Louisville during inspections. You’ll notice that the mortar was installed around the stones and it was also laid directly next to the window frame. The is no form of expansion gap, and the weep screed is missing.  Every important detail was skipped.

ACMV Failed Window Install

Here you can see the stone and mortar butted to the window. This will crack out over time and allow water to seep in around the window.

Window and Door Jam Details

The sides of windows call for the same backer-rod and sealant as the top, to allow for thermal movement. Remember from science class that almost everything expands and contracts when it heats up and cools down. We must allow for this movement, and flexible sealants are the best way to do so. We incorporate bond breakers like backer-rods  to help cut down on the amount of sealant used, and to keep the bond in the joint even.  I drew a couple of diagrams to help you visualize what the backer-rod/sealant joint would look like.

Backer-rod ACMV Control Joint

Here is an example of a properly sealed joint using backer-rod. This will expand and contract with thermal movement and keep things water tight.


Let’s look at a detail where the backer-rod is missing from the equation. When you don’t utilize a backer-rod, the sealant will flow and move inside the joint and grab more of one side than the other.  Think of this as a game of tug-of-war. One side has 10 people, one has 3 people. Who’s going to win? When one side is stronger than the other, the joint will fail and pull apart. This is what happens when you see a caulked joint that has cracked and opened up.

Sealant Missing Backer-rod

Here you can see what happens to the sealant when the backer-rod is omitted. The left side is going to win every time.


Here is what a typical install of ACMV around windows looks like in my area.  I’ve never seen an installer use backer-rod and sealant. It’s always either mortared straight to the window jam, or “dry stacked.” Both are a recipe for failure.  You know the old saying, “If you fail to plan, you plan to fail.”

ACMV Window Jam Failed Install

Here is what the sides of a window install will look like with the backer-rod and sealant missing. The mortar is installed right up to the jam.


Window Sills

One of the most important details with a waterproof installation of ACMV on your home should happen long before the stone veneer is ever installed. The opening for the windows must be wrapped in sill flashing.  This is usually done with a peel and stick product such as Grace Vycor Flashing.  If this step is omitted, compounded with the other skipped details, you will be left with water that will seep in around the corners of the window sills, and rot out the wall.  How fast this happens all depends on how much water gets in.



Window sills are treated like the sides of the window. There should be a 3/8″ gap between the faux stone and the window. The gap gets the backer-rod sealant to keep water out.


Leaking Window ACMV

This home had failure at the window corner. This picture was taken during the exploratory phase of the repair.


ACMV soaking up moisture

This window is missing the sloped sill material. It was also never caulked around the window jam. Notice how the bottom right corner is much darker than the rest of the wall. That is because it’s taking in water here and stays wet.

Identifying A Problem

Even though I have never seen an installation of ACMV that I would consider correct, I have seen several houses that are not showing signs of problems (to the naked eye).  Sometimes it take the Perfect Storm of circumstances before real problems pop up.  Sometimes it takes the right amount of rain exposure.  Sometimes enough time hasn’t elapsed for a water problem to manifest itself on the surface.

When I can’t simply look at the home and know there is an issue, I use technology to help out.

Moisture Meters- I carry several different kinds of moisture meters.  Each tool does one particular job well, and the specific task dictates which one I reach for.   When dealing with ACMV and windows, I use my GE Protimeter with deep wall probes.  Yes, it’s expensive, but it’s a drop in the bucket to what the repair costs on your house will be.

Your wall cavity is about 4″ thick.  Most of the time, the moisture will take years and years to show up on the inside of the home near the drywall.  However, using the wall probes, I’m able to take moisture readings through the 4″ of wall cavity and reach the backside of the substrate (the OSB plywood on the outside).  This surface is what the ACMV is actually mounted to.  If water is leaking in, the meter should find it.

To use the probes, I first drill two small holes in the drywall. Sometimes we get lucky and find an electrical outlet near the bottom of the window. When that happens, we can remove the cover plate and slide the probes between the electrical box and the cutout of the drywall. This keeps me from having to drill holes in the wall.

ACMV Deep Wall Moisture Scan

Once you drill two small holes in the drywall, the probes can be pushed through the wall cavity to take a moisture level reading while doing minimum damage to the wall.


As with other claddings used in construction, the details around doors and windows are what must be perfectly executed.  Flat walls are relatively easy; it’s when a change shows up in the  architecture that builders and contractors must follow details, or things go south in a hurry.  If you’ve compared your home to what I have detailed here and you’re concerned, I encourage you to reach out to a moisture intrusion expert to have your home examined.  If you are in my area, Louisville, KY, please feel free to contact me about getting your ACMV Inspection.


In part three I show you how the details around the walls should be handled, and how to make sure the water doesn’t build up behind the stone veneer.

The ACMV diagrams from this series were all taken from the MVMA guide. I will sometimes remove extra details or color certain sections to make them a bit easier to understand. If you want to look at the originals, download the full MVMA manual.

ACMV-Adhered Concrete Masonry Veneer- The Next Big Problem in Construction

It’s all the rage these days; fake stone siding (manufactured stone) as an accent on the front of a house.  You can give your home that mountain cabin look, right here in suburbia.  Manufactured Stone ACMV InstallSiding (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 rocks.  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. 

Story Time

A couple of years ago I was called in by a homeowner 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 so wet.  I was able to trace it down to the manufactured stone siding on the front of the house.  The builder had omitted all the important details with the install.  That day was began a fight with his builder that would last 2 years. For that entire period, his dining room was blocked off and unusable. The result: Attorneys were hired and things got ugly. The builder eventually repaired all of the water damage, stripped all the ACMV 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 a 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 siding.  When I am inspecting homes in Louisville KY, I refer to that guide and its details to show my buyers 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 that when it comes to a home…

The Devil is in the Details

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 ACMV 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.


A wise man once told me that water and women can be lumped into the same category: They both always win. Never is that more true than when it comes to the 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 rain water, 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 wood framing, 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 glowing red area.  This allows the moisture a path to escape.

Brick Veneer Air Space

Here you can see the air space in a typical brick veneer wall (red space). The moisture is given a place to drain at the base of a wall. When done properly, this keeps things nice and dry.


ACMV (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 “stuck/mounted” to the framing, and not resting on the wall foundation in front of it (like brick veneer).  If you want a trouble-free install, you must create a drain 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 around here are simply are not installing them.


Here is the first image you come across in the MVMA install guide. I’ve highlighted the drain parts in red at the bottom of the wall.

There is a better way to build it

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 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 to 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 and make work.  ACMV Furring Strip Detail

Here is a detail for the use of a drainage mat used in place of the furring strips.  This too, creates that air gap between the manufactured stone layer and the structure of the home.  ACMV Drainage Mat Wall


What to look for on your house

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.  If you are in the Louisville, KY area, 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.


In part two I talk about what should happen when you introduce doors and windows to your faux stone installation.


In part three I show you how the details around the walls should be handled, and how to make sure the water doesn’t build up behind the stone veneer.

The ACMV diagrams from this series were all taken from the MVMA guide. I will sometimes remove extra details or color certain sections to make them a bit easier to understand. If you want to look at the originals, download the full MVMA manual.