How to Remove Samples
When investigating problems with an EIFS project, sometimes samples of the EIFS are taken. Taking samples can have several purposes, such as providing a piece of the wall for testing, as well as allowing one to see what is happening inside the wall. Either way, it’s often a useful exercise. There are lots of ways of removing sections of EIFS from a wall. This month’s column will give some tips on how to remove samples.
Although not a “sample” per se, the pair of pencil-size holes that occur when moisture meter readings are taken do need to be plugged. Long probes must be used to get through the insulation layer and into the substrate and framing. Ram the long probes through the EIFS and it is likely one will bend the probes and thwart the ability to take moisture readings. Thus, first make pilot holes through the EIFS lamina. It’s not necessary for the pilot holes to go through the insulation, as it is soft and the probes will go through it easily.
Hint: I use a nail set and a hammer to make the holes. First, I drill some holes that are slightly larger in diameter than the probes in a 1/4-inch thick aluminum bar. The hole spacing is the same spacing as the probes. That way I’m sure the long probes will fit through the EIFS lamina, without bending them.
After the reading has been taken, the holes need to be plugged. I use sealant that comes in a toothpaste-type tube. Since most EIFS finishes are acrylic, acrylic sealants work well as they stick to themselves. Clear silicones also work, especially if you cannot get a good color match.
Small cutsCutting small samples, to see why something is cracked or to peek into the wall, can be done in a number of ways. A hole saw and a high-voltage cordless electric drill works well. EIFS coatings are highly abrasive, so bring a replacement drill bit. Bring extra batteries, too. Cordless drills work and are especially handy on ladders, manlifts and swing stages, and other places when power is in short supply. Make sure the saw has tungsten carbide teeth, otherwise the drill will get dull immediately.
The hole saw needs to have a deep enough barrel that can get all the way through the insulation; longer still to get through the substrate. The foam will get up into the barrel of the saw and can be a devil to get out. But first get the sample out of the wall. Rocking the drill back and forth gently will usually snap the foam. Try using a hole saw that has large slots on the sides and large holes where the bit meets the drill chuck. This will allow you to wriggle out the foam and coatings without mutilating them. Better yet, try making a disk out of masonite that just fits down into the barrel of the saw. Then, after you’ve drilled the hole, press the masonite through the hole in the mandrel and force the foam plug out without mashing the foam.
Now that there’s a hole, how does it plug? If looking for a look-see into the wall, then put the sample back and caulk it shut. If retaining the sample, here’s an easy way to seal the hole: Get a hunk of foam of the same type and thickness used on the wall. Using the same hole saw, drill almost through the foam. Then push the drill. The foam plug will snap off, with a bit of foam hanging out of the end of the drill. Then gently wriggle the foam plug, and draw it out. This is a lot easier than trying to get the foam plug out from being stuck up inside the saw barrel.
One will probably need to shape the foam plug to fit the opening. At very least trim it so it does not hang out past the outside face of the EIFS. A hacksaw blade in a hand grip, some coarse sand paper, or a keyhole saw, works well. One can even use the EIFS finish on the wall to “sand” the foam plug.
To do a quick, temporary patch, dab a big blob of sealant on the inside end of the foam, and then put a ribbon of sealant around the shaft of the plug. Then stuff the plug in the hole. If you’ve used enough caulking, then it should stay in place. Then place a big blob of sealant across the outer, exposed piece of foam. Gently smear the caulking onto the foam and onto the adjacent EIFS finish. If the color matches closely, it makes a neat patch. One can even get fancy with a towel and give it some texture by dabbing the surface. Remember, this is a temporary patch and mostly serves to keep water from getting in for the short term.
Cutting loose a large sample can be done several ways. A circular saw with a masonry blade can be used to precision cut the EIFS all the way to the substrate by adjusting the blade height. Obviously, the thicker the foam the larger diameter saw blade is needed. This creates a lot of dust, so protect yourself. Another option is to cut through just the lamina using a diamond grinding wheel. Then use a hot knife to slit the foam back to the substrate. Remember that a hot knife works only with EPS and not with polyisocyanurate foam. With poly foam, try using a thin-bladed knife or saw.
The hard part is getting the foam loose from the substrate. Adhesively attached foam is difficult at times, as it may be fully bonded to the substrate. Likewise, mechanically attached foam can be a devil too, as the foam tends to get mashed by prying it loose. Work the sample a bit in order to remove it in usable condition.
If the EIFS is mechanically-attached, use a magnetic stud finder or a Tramex scanning type moisture meter (“Wet Wall”) to find the fasteners. Then take the sample at a spot where there is not a fastener; the sample will simply fall out.
Size importantSample size is important. If you are trying to do some sort of physical test, such as measuring the bond of the various EIFS lamina layers, take a sample large enough to get a good grip on it in the test equipment. Keep in mind that the foam is relatively weak, so if trying to pull on the foam, the foam will probably fail first, leaving a worthless partial piece of a sample. Small “plugs” of EIFS, taken using a hole saw, are often adequate to get an idea of what’s in the wall, and to do basic, small scale chemical tests. The minimum diameter for round “plug” samples is about 2 inches. Plugs larger than about 31⁄2-inch diameter require a sturdy drill. It’s often better with large samples to make rectangular cuts.
Clearly, with large samples, the smear-the-caulking technique described above is not the ticket for making a patch. Large holes should be patched the same way that a patch is done when repairing impact damage. This involves cutting out a rectangular hunk of the whole EIFS and then attaching it to the substrate. The basecoat adhesive, mesh and finish are then applied. EIFS manufacturers have detailed instructions on how to do this.
With the sample, store each one individually in a clear zip bag. It’s smart to mark up on the building’s elevation drawings with the location where they were taken, as well as the date and some sort of unique identifier for each sample. A before and after photo is handy too. Write the sample number, date and project name on a slip of paper.
Attach the note to the EIFS by pushing a push pin through the note into the EIFS lamina. This tag can then be placed in the storage bag and can be seen from the outside.
Maintain control of where the samples go during their life. This is sometimes called a chain of custody, and helps people know who has what samples, where and when.
How many samples needed to take requires some planning. The more taken, the more holes will occur on the building. But take enough so that the sampling is valid. In other words, just a sample or two often is not predictive of the overall condition of the building; take enough for the sampling process to be statistically valid.
Make sure permission is granted to take whatever sample is removed, unless you own the building. It’s good form to try to take them in areas where the patches won’t look so bad—in other words, not at the main entrance. Also take samples of whatever the various types of alleged problems there are, such as cracks vs. stains vs. delamination, and so on.
If working on a stud wall and cutting through the sheathing, keep in mind that the stud cavity may have wires or plumbing pipes in it. You could zap yourself or flood the wall cavity by cutting into a 120-volt power cable or a water pipe, so be careful!
Like a human being that is sick, EIFS buildings can have problems that are not obvious from the outside. Thus invasive investigation techniques are often the only way to be sure of the wall’s actual condition. Unfortunately, EIFS, unlike many other building materials, cannot be disassembled and then reassembled, without ruining the EIFS in the process. So be prepared to spend a couple of days patching the holes after the samples have been taken. W&C