17 October 2010

The Stove Wall


Started a fieldstone veneering project about three weeks ago and finished it up last night. The space is located close behind a wood stove, so wallboard or wood was never possible there for the homeowner because it would be a fire hazard according to the local code. All heated elements of the stove need to be 18 inches away from wood (the upper beam's length from the stovepipe is just over 18 inches (whew!). But stone is a fine material to use in an application like this, and really fits with the rest of the house (there is a stone-lined wall directly above this on the first floor), and accentuates the post-and-beam feel in this walk-out basement. The measurements of the wall to be veneered are 7 1/2 feet tall by 9 feet wide.

I hung up the wire lath material last winter in anticipation of getting to it this season when the wood stove was idle (the cement would harden too fast if applied while the stove was in use). With it being against a cinder block wall, the easiest way to secure it was with a Duo-Fast ram-fire gun that used .22 cartridges that propel a 1" cement nail. I placed a #10 washer over the ram gun nail before I fired it so it would be sure to catch the mesh, rather than just go straight through a mesh hole. It took 4 pieces of lath, which had to be cut both for fit and stovepipe and ash door openings. The lath is very sharp, but my usual heavy-duty rubber-lined gardening gloves stood up to it nicely. These types of glove provide a great balance of protection without losing so much tactile grip.The lath is the best material and method to use because it adds a great amount of strength to the project. A bond between previously hardened cement and new cement is prone to failure if materials or specialized liquid additives aren't applied or used. With the lath, the cement hardens around the meshing and gives a strong bond.

Getting to it three weeks ago, the first step was amassing the stone that I'd be using, which I tried to keep at about 2 inches of thickness, give or take, so it wouldn't jut out too far from the 2x8s that frame it in. Some masons like to lay out a pattern on the floor and apply it piece by piece rather than determining fit on the fly. I didn't really have that luxury, but it went all right regardless. That process would be something to try to see if it quickens the pace, but as it went I don't think it would save all that much time. There would also bound to be problems in the translation between the theory of the layout and the reality of when stones go up on the wall. And I think it would kill some of the improvisation and artistry that goes into a wall like this. For example, using a photo from an old magazine as inspiration, I put in some metal tabs for support and laid in a small shelf on the left side.

I took some pictures showing the process that it takes to place a stone. This isn't intended to be a step-by-step of tools and instructions --- that is available in how-to books --- but I'll share my process here quickly, with accompanying pictures in an order that I hope this Blogger software doesn't totally boggle.

First, the stones have to be clean of dirt and debris to ensure good bonding with the cement. The cement should be mixed to a consistency that is often described as peanut butter. Those unaccustomed to mixing cement should be careful and add just a small amount of water at a time. Before applying to a stone, I take a trowel of cement and do several drops of it against the bottom of the mixing tub. This brings out some of the water to the outside of the ball of cement, congeals it a bit into a shiny surface, and makes it a little cleaner to work with.

I wet down the back of the stone because a dry stone will tend to suck out moisture from the cement too fast. I applied cement to the back of the stone, then tapped it down with the side of the trowel, making a score mark pattern, which helps the cement get into the tiny cracks and crags of the stone. I applied the stone against the lath in the position that I wanted it in, and did an initial press-in. Most stones required some wood shims (the wood lets go fairly easily once the cement is dried) to keep a consistent thickness for the finish grouting between stones. The exact time of when to add the shims is dependent on each individual stone's fit and steadiness against the wall. If shimming can be held off briefly, it will reduce the amount of clutter in the way of tapping and troweling.




I used a rubber mallet to tap the stones into place and to force the cement to work into and behind the lath. This is also accomplished with a trowel for smoothing the cement and, in tight spaces and odd corners, fingers must be used (I recommend wearing latex gloves when touching cement for any length of time, as it takes a toll on skin).

Some stones didn't require bracing, but most did. Obviously, as the stone courses got higher, the bracing boards needed to be longer. I leaned them against the stone, kept pressure toward the wall, and butted a stone on the floor behind the brace to hold it in place, and did a few gentle taps on the floor stone with the rubber mallet toward the brace to secure it.


After each course of stone was laid, I brushed them off with a brass-bristle wire brush to remove cement spots. This can get pretty dusty, and wears away at the brushes pretty fast.

The last step, once most of the stones were up on the wall, was filling in between them with cement. This was the most labor-filled part of the project. Tried using a grout bag, but the consistency of cement needed for it to flow out was a deal-breaker on this axial plane, as it would have run down the face of the stones. So, it took a while of shaping small balls of cement and pushing them into the joints (which when placing the stones, I tried to keep at about a finger-width). I usually tried to split the difference and meet at the perimeters or edges of the stones that are in a particular spot. This is also the point where I would fill in smaller gaps by pushing in small stones into the already-packed joints and then smoothing the cement around these space-fillers. I generally tried to keep a slightly concave U shape to the joints, similar to the grouting on traditional brickwork. Then wire-brushing should be done when it was almost dried. This final brushing is one of the critical points in how each stone is going to be showcased. As I just wrote, I generally tried to stick to the tradition slightly concave U shape, but there are some special considerations, such as where a few stones stick out farther than the rest. This is the opportunity to show off a bit of their profile rather than grout all the way to their edges. As much as stonework is about brute heft with a fixed, matter-of-fact purpose, there is a lot of room for artistry.


Following the final wire brushing, which leaves a lot of cement filings, I did clean-up with a Shop-Vac that has an insert bag, so as to keep the cement dust from simply recycling back into the air and redepositing on everything. This vacuum is also powerful enough to get all of the dust so it won't be tracked all through the home. I used the brush attachment to go all over the dried stones, to vacuum off whatever dust and bits of cement that were left, and then the 1/2 inch of the previously mentioned cement filings on the floor. Then again, clean-up is something that happens every day as I try to keep the area organized. Bits of cement fall to the floor --- it's a fact of any veneering like this. In all, six 80-pound bags of  S-type cement (the recommended type for veneering projects like this) were used. And proudly, I can say that the cement wastage I collected over the three weeks would fill about a gallon milk jug to about three-quarters. Not too bad.

It was a process of finding fits and trying to fill gaps (there were a lot of V-shaped gaps while setting stones that I was a little worried about, but which really melt into the picture once finished). There were small trials of having to support stones over the ash doors so they had nothing to rest on at the bottom. There were a few spots where the cinder blocks jutted out a half-inch or more than surrounding parts. You innovate and work around it, you save this thin stone for that spot. No big deal. I was able to use mostly medium-sized stones in this wall, several large stones (one up high on the right side that I particularly like) and some small stones and it all came together in a consistent pattern.

I'm very pleased with how the wall came out. A feature like this is a real eye-catcher and really turned around the look of this area for the homeowner. The time on it was about 120 hours.