Making a table?
May 23, 2005 7:16 AM   Subscribe

I want to make a table.

I got a nice cast iron table base, and have had it powder coated. I'd like to use a two by two square of slate as the top.

How do I attach the slate to the base? Many tables like this I have seen have a piece of plywood sandwiched between the top and the base, are they connected with glue? What kind? I plan on leaving this table outdoors year round, and don't want it falling apart.

Also, should I apply a finish to the slate? What kind?
posted by Marky to Home & Garden (11 answers total)
You tweaked my interest with this one. It sounds like an interesting project and now you have me interested in trying something similar. Google identified this Home and Garden Television project as a starter.
posted by caddis at 7:28 AM on May 23, 2005

To protect the wood outdoors apply spar varnish to exposed wood surfaces. This will likely need applied every year or few years depending upon the environment. Also, make sure you use an outdoor grout between the tiles.
posted by caddis at 7:41 AM on May 23, 2005

You should be able to use construction adhesive to attach the piece of plywood to the underside of the slate, and bolts to attach the wood to the base. Something like:

1) Drill holes straight through for the bolts, then drill out larger countersink circles to let the bolt heads sit flush or under the wood surface.

2) Put the bolts in (with washers). (You might put a dollop of construction adhesive in the hole to stop the bolthead from spinning later.)

3) Glue the wood to the bottom of the slate slab.

4) Bolt the slab to the base.

Of course, that presumes that you can find or add places on the base to use as boltholes.
posted by LairBob at 8:03 AM on May 23, 2005

If you attach the slate to a piece of plywood, you're essentially tiling, and may want to ask the friendly folks at the Tile Your World Forum. Basically, though, you'd use thinset to attach the slate to plywood. For a piece that large, you'd comb the thinset all in one direction to avoid voids in the thinset coverage. You can use a sealer or enhancer on the slate for protection. The forums have good information about both these issues.

Aesthetically speaking, you may wish to attach the slate directly to the base. This may be a bad idea if your slate is too thin; I'd ask the folks over at the forum on what "too thin" is but I'd offhandedly guess less than 1/2" or so (depending on table use and flakiness of the slate). If you're going this way it would be more difficult, but not impossible--I'd probably use an epoxy to attach brackets to the bottom that would allow the top to be secured to them.
posted by RikiTikiTavi at 8:41 AM on May 23, 2005

Response by poster: I guess I wasn't really clear about the top, I plan on using one piece of 1-1/2" thick slate as the top—the kind of stone normally used for walkways.

LairBob, what kind of wood would you suggest? I'd guess an exterior grade plywood, but I don't want to buy a 4'x8' sheet just to cut off one square foot.
posted by Marky at 8:58 AM on May 23, 2005

Marky, as to your last: Home Depot and other mega-stores have been selling smaller pieces of plywood for some time: half sheets, quarter sheets, circles, etc. Usually in the trim/millwork aisle.
posted by misterbrandt at 9:16 AM on May 23, 2005

You might want to think about the potentially sharp edges of that slab of slate, and the nature of slate which chips easily. In commercially sold slate-top tables (try Froogle for examples) there is a metal edge, part of the base, around the slate.

In the long run, you might be happier if you put a hardwood edge, mitered corners, all the way around the slab, attaching to the aforementioned plywood base. You could either make it a vertical edge, enlarging that table by the thickness of the board all around, or a horizontal one, enlarging the table by the board's width (this would have to be at least the thickness of the slate, maybe a little more so it could be routed to fit around and hide the plywood.)

For outdoor use, this edge could be made of teak or cedar and would work fine without any finish. I would not put a finish on the slate, either, unless you think people are going to spill greasy food on it, or something.
posted by beagle at 9:51 AM on May 23, 2005

I really like beagle's idea of putting a wooden edge around the slate, if it's got a clean enough edge to the sides that you can do that. Otherwise, you're risking having a tabletop that starts crumbling around the edges.

As for the best wood, a good plywood would probably be fine. My only concern would be the thickness, since if you countersink the holes, you're losing width of the bolt head (plus a washer) at each anchor point. The tabletop itself is going to be pretty heavy, so if you leaned on one edge, you could be putting a lot of tension on the opposite bolt. (On the other hand, it's not going to be a very wide top, so you wouldn't be piling up an awful lot of torque.) If you had any concerns about the plywood, you could go with a little thicker piece of hardwood.

The strongest option would be to get some of those little steel plates with a bolt hole in the middle that already have a dimple in them--you could just glue a few of them to the slate instead of using wood--but I think wood would give a nice feel to the table. A cast iron base, joined to slate with steel connectors, would probably feel very hard and clangy. A layer of wood would add a little warmth to how it sounds and feels.
posted by LairBob at 10:58 AM on May 23, 2005

Marine grade plywood will be much less likely to buckle or delaminate because of the water resistant glues, etc. One piece of slate or not, moisture will get in, even a single piece of hardwood might well warp. Trim the outside rim with with marine teak trim pieces attached with brass screws. Fill the screw holes with epoxy. Basically, build it like a boat if you want to keep it outside all year.
posted by Rumple at 12:29 PM on May 23, 2005

Yup. Marine plywood will give you the best resistance to weather (you'll still have to finish it with spar varnish or similar).

Instead of drilling holes and dropping bolts through, later hoping that they won't spin when you try and tighten them up, drill the holes and use "tee nuts". They provide a threaded barrel and spikes that dig in to the wood to stop them spinning. You then put the bolts up from the table base.
posted by 5MeoCMP at 1:29 PM on May 23, 2005

If this were my project, I wouldn't bother with wood - at least assuming that the base has rails all the way round at the top, not just the tops of legs. I'd just glue the slate straight to the base rails with copious quantities of silicone sealant.

I'd start by running a bead of silicone around the top of the rail and letting it set for a couple days, to make a resilient cushion for the slate to sit on while the rest of the sealant sets; I'd want a minimum of about 4mm of silicone between rail and stone at every point (less than that and it may tear when set). Once the first bead is set, just slather the top of the rail with silicone, sit the stone on top and give it about a week to set before trying to move it.

The rationale here is that you've got a weighty piece of stone sitting up there, and it will basically want to stay put; the silicone will be more than enough to avoid it sliding off when bumped.

Leave the stone unsealed. If you're really lucky, you might get a bit of lichen growing on it.
posted by flabdablet at 6:02 PM on May 23, 2005

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