Granite Countertops

[DonTx]

I need either some standards or installation instructions for granite countertops.

Two of the issues I have is the use of a sub counter and moisture barrier (are they needed/required) and where seams can occur.

On many jobs, I see the seams at the sink. My Residential & Light Commercial Construction Standards book says seams should not be near sinks, but they give no references.

Any suggestions?

[chrisprickett]

Originally posted by Donald Lawson

I need either some standards or installation instructions for granite countertops.

Two of the issues I have is the use of a sub counter and moisture barrier (are they needed/required) and where seams can occur.

On many jobs, I see the seams at the sink. My Residential & Light Commercial Construction Standards book says seams should not be near sinks, but they give no references.

Any suggestions?

Going back to my kitchen days... Generally fabricators will try to seam (if a seam is needed) at the sink cut out or cook top cut out, to minimize seeing the seam. With granite, you'll almost always find a seam at the corner of an L shaped countertop.

In a perfect world, there would be no seams. Because garanite is a natural product, it doesn't come in 4x8. I can be almost any size. Seams occur for the following reasons:

1. The desired counter is larger than the granite slab, or slabs, chosen.

2. The granite top must not be too large for manageable transport, getting it through doorways, and safe handling.

3. Some tops will be made of smaller, multiple slabs. This can be true of a cheaper top, or a rarer top that isn't quarried in large pieces.

Regarding the sub-counter, it's usually 3/4" plywood. It can be other materials, I've seen it installed on steel tube frames. No moisture barrier is required.

[BADAIR]

Donnie,

Here's a couple of counter top links with installation standards. Hope you find your answer. The seam issue is a concern when not properly sealed. One trick posted on another BB is to try and slide a piece of paper between the seam to check for sealant on a clear or invisaseal job. At least we can document that seams are sealed. I have used pressure treated 3/4" ply with multiple coats of water sealer for bar tops no moisture barrier. One of the 40'x11' U-shaped bar jobs that I had done in ' 97 was just torn out last year with NO signs of moisture besides a few stains. Wish I could of salvaged the granite for my place, alas they reused it for the newly designed bar...

http://www.marble-institute.com/industr ... /index.cfm

http://sitelevel.whatuseek.com/query.go ... 9330dc8003

[Jim Baird]

Recently I read about granite tops needing to be sealed to prevent stains. The advice-giver even went on to recommend "avoiding spills" on yer granite!

Can't figure why the stuff is so stylish, with the weight, the expense, and the need to prevent spilling stuff on it.