Thursday, August 27, 2009

Coping being cut

Our in-ground pool is actually raised out of the ground slightly (18 inches near the house). This makes the side a nice bench to sit on, keeps cut grass from blowing into the pool, and should interfere with running and jumping into the shallow end at a steep angle.

One consequence, though, is that our coping stones are a nonstandard width. We've decided to have bullnosed coping (so these are bullnosed both sides, also nonstandard), and that requires that the coping overlap the waterline tile by over two inches. This kind of thing adds up:
  • Waterline overhang: 2.5 inches
  • Tile thickness: 0.25 inches
  • Thinset: 0.375 inches (that's a lot, to give the mason plenty of freedom to flatten the wall for the enormous glass tile mosaics that are going in)
  • Bond beam: 12 inches
  • Thinset: 1 inches (the outside of the bond beam is quite uneven)
  • Facing stone: 1.25 inches
  • Exterior overhang: 2.5 inches
All up, we've gone for coping that is 20 inches wide.

We actually had a order placed for some very nice pearl white travertine (from Olympic Stone). When it came time for them to come by and pick up the check... they didn't. We called back and found there was some sort of problem... they didn't actually have the stone. it would be a 3 month delay to get it from Turkey.

Well, that's never a good thing to tell a customer. Martha started looking around, and found another very nice stone, this one a three color granite, from American Soil. This one is more expensive, but it really is pretty, and it's available right now. We ended up buying it. (We may use OSM's pearl travertine for the face of the pool rather than the coping, since they apparently have the 1" stuff available.)

[Update 16-Nov-2009: The pearl against the walnut travertine ended up not looking as good as we'd hoped, so we ended up using the walnut travertine on the sides of the pool. You can see this in the mid-November post.]

By "it", I mean a 12 ton boulder imported from Columbia, California. You can get a sense of scale from the pickup truck at the back right. This rock is a little shorter than I am.

It came from over here:

They're chopping this thing up into 20 inch wide by 36 inch long by 2 inch thick coping stones for us.

This is a cable saw. The cable has some kind of abrasive on it (I've never actually seen the thing stopped, it appears to be running all the time). The huge wheels drive the cable through the stone. Above and below, they're whacking the top off the boulder.

Below, they're cutting the ends off. In this pass, the rock stays put and the machine basically drops through it at a half inch per minute (I'm not really sure, as I never saw the saw make any noticeable progress through the rock).

Here's one of the slabs coming off the cable saw, going into their indoor facility for shaping. You can't really see all the color here, but there is white, black, and some pink to it.

Here's the rock all chopped up:

There's a lot of white in some of these. Hopefully they'll be able to cut around that to some extent.

Not so much in others.

This equipment is usually used to make countertops.

American Soil just got a brand new Italian machine for cutting and bullnosing. This isn't it, since apparently that machine can't cut a straight line just yet.

Each stone should weigh about 140 pounds. I'm sure the mason will be very happy to hear that.

I'm really happy with how this looks. We still have some risk, in that the coping could have huge blobs of white in it, or the grain could get mismatched, but the folks at American Soil seem to be on top of that.

We've also picked up all our glass tile. It gets installed after the coping, but I'll try to post some pictures of the pieces assembled in our garage so you can get a feel for it.


  1. Beats the hell out of that tile cutter machine I used. Pretty amazing.

  2. The tile cutter you used is probably going to be used to trim a couple of these coping stones when we do the installation. I intentionally designed the stones so that there is an extra couple of inches along each side of the pool. We'll work from the corners to the middle, and then trim the middle stone to fit. This trim operation will take out any error in my measurements or American Soil's fabrication.

    I'm going up to American Soil today to check on progress. Apparently somebody punched the wrong button on the machine and they don't know how to reset it to it's default configuration, and so they don't know how to program it to bullnose my coping stones. Supposedly the guy who will show them how to do it is coming today, so I want to check the first articles.

  3. I am interested to see images of the finished bull nosed coping stone and also of the coping and glass tiles in finshed pool. If these are posted pl inform link.

  4. You can see one shot of the finished bull nosed coping here:

    The glass tiles in the finished pool have not been a success. About 2 years after filling the pool, they shattered in such a way that the kids can cut their feet on them. I still don't have a good explanation for what happened, but I have been able to reproduce one of the two failure modes by swapping tile samples back and forth between boiling and freezing water.

    I've been told that other glass tile which is sold specifically for swimming pools will not fail in the same way. When I apply my freezing/boiling test to samples of this better tile, it survives much longer, but it still fails. Porcelain and granite tile does not fail, even after ridiculous numbers of test cycles. We are going to redo the pool interior, probably in granite tile and plaster, probably at the end of the 2012 summer.

    1. Your finished bull nosed coping looks wonderful.

      Have you finalised on going with granite tile? Is the tile the same type of granite as sold/used for kitchen counters?

      How will granite stand up to pool chemicals?

      My India, in ground insulated pool construction has just started and I need to select porcelain / glass tiles or granite tiles or granite slabs. Granite is cheap in India about $2/Sq. Ft for 0.75 thick slabs of 2 Ft X 8 Ft. Can be had cut into smaller tiles at about $1.50 per Sq. Ft.

      In India best way to adhere Granite to plaster walls is with a hydralic adhesive sold by Saint Gobain ( France company) in India but I do not know how well it would hold in swimming pool. What adhesive were you planning for your granite walls?

      My first thought is to use large 2 Ft X 8 Ft granite slabs to minimise the grount lines and simplify maintenance?

      Any comment would be welcome.

  5. Thanks. I think the single aesthetic thing we're happiest with is the coping stone.

    In doing research on granite for our pool, I found that the lighter shades of granite have higher porosity. Apparently it's a direct relationship - the lighter stuff is quartz which shrinks more as it cools, thus the porosity. Although I don't expect much difficulty, all the granite we will use around the waterline will be black or dark blue granite. We'll mix in some lighter stuff for some of the below-water mosaics.

    I expect the granite to be completely impervious to pool chemicals, far more so than the plaster and nearly as much as the glass. It might be susceptible to stains from iron or other metal oxides in the water, as will the plaster. The only way to fix that is to ensure your pipework has no metal, and if it does (heat exchangers), make sure that metal is titanium or maybe 316 stainless steel.

    I talked to a granite fabricator in Florida who did his own pool and four others in granite ten years ago. He put in NO EXPANSION JOINTS and NO GROUT LINES, and fabbed everything, including the waterline, from 2' x 8' slabs butted up against one another. He's had no problems. I am going to follow his example.

    Even with epoxy grout and careful attention to the pool chemistry, I've noticed that in our pool the grout grows calcium deposits, but no the glass surface. I expect something similar with the polished granite. Just as you say, we expect to minimize maintenance by installing the granite tile without grout lines and expansion joints.

    We will use the same stackup we used before:
    Plaster was Quarabella, by General Cement. Grout was SpectraLock. Stackup was:
    * Gunite, which cured for 5-8 months before tiling. Aqua Gunite did the job.
    * Hydroban, which is a Laticrete product which paints onto the gunite and makes a watertight seal, should the joints between the plaster and tile, or grout and tile, leak. It's also supposed to allow the tile to move a little.
    * Thinset: Hydromet Reflex, white.
    * Deck mud, bought at Home Depot. This was screed flat, about 1/4" to 1/2" thick, then allowed to set up a bit
    * Tiles were back-buttered with the same thinset and then mounted on that mud
    * Excess mud around the tile perimeter was cut away.

    This worked really well: we have no examples of the adhesive failing before the tile. The only thing I wonder about is the possibility that either the thinset or the deck or wall mud shrank differentially compared to the plaster, or just shrank enough to put the tile under stress. Could that have caused our glass tiles to shatter? I have asked experts, and I still don't know. The most likely explanation is that the glass we used was simply unsuitable for immersion, and suitable glass would have worked fine. It's definitely true that the thinset shrinks quite a bit when it cures... that's why you put it on thin, and let the screed mud take the flat dimension.