SFA

Long time reader. First Post

What is an acceptable thickness variance within a slab. I could not find anything in the MIA design manual. Is there a standard out there.

We just recieved two slabs of which the thickness varies from 15/16" to 1&3/16" within each slab. We needed material for a project with an island size of 130". The slabs were selected by a customer from pictures from a reputable supplier's stock. I just started cutting the slab late yesterday and ran into an issue with setting the ogee hieght on the CNC since the material was as small as 15/16" in some locations.

The slabs are first quality and were very expensive. (Double the cost of Antique Brown). Does first grade material mean a greater tolerance in thickness variance? What are the responsibilities of the supplier?

Please advise.

Phil DiMambro
Dimanti Stone Works
Windsor, Ontario Canada

I've never seen a standard that dictates uniformity in slab thickness. 1/4" is not an acceptable variance in thickness within a slab, especially in your application.
In my opinion, the supplier needs to help you out on this, given the excessive variance.

I agree. Our suppliers have always replaced the stone in cases of extreme variances, not that it happens often.
We once cut a slab that was thin in the middle and our supplier still replaced the slab even after we cut it.
Call the supplier and get them to replace the stone then explain to the customer the issue.

From Section 17 (Countertops) of the MIA Design Manual:

10.4 Slab Thickness. The thickness of the stone slabs used in a given project shall not vary by more than 1/8" (3 mm) between the thickest and thinnest slabs.

There is also a specification for flatness across a slab.
Is your supplier an MIA member or claim to adhere to MIA standards?

Good luck.

There are times when the thickness problem isn't visible until the slab is cut. We had a 3 slab job, 2 cm laminated edge, and when cutting the 3rd slab found it was onle 9/16" thick in the middle. No other slabs available. The custy purchased the slabs. Ended up re-fabbing out of new slabs from new supplier and the custy filed against the original as they would not step up. Never did hear how that ended.

Mark Meriaux wrote:From Section 17 (Countertops) of the MIA Design Manual:

10.4 Slab Thickness. The thickness of the stone slabs used in a given project shall not vary by more than 1/8" (3 mm) between the thickest and thinnest slabs.

There is also a specification for flatness across a slab.
Is your supplier an MIA member or claim to adhere to MIA standards?

Good luck.

Can someone let the Black Galaxy Quarries know this!!!

Black galaxy... amen! Here it is the saudi colors: TB, GL, and violetta. We just had one that had a 5/16 difference.

This is getting to be a regular thing. slab thickness, also polishing swirls on surface, I have recently received bundles of slabs with swirls all over and thickness problems. I find over the last few years the slab cutters have been slacking.

So your sayin your 3cm slabs are under an 1" thick in areas? We've had thin 3cm Slabs before but never under an inch!

Time Consuming..... but if your supplier gives you the run around you can always even them out! 3cm Ogee Edge wont look right on 15/16" though.

Danno wrote:This is getting to be a regular thing. slab thickness, also polishing swirls on surface, I have recently received bundles of slabs with swirls all over and thickness problems. I find over the last few years the slab cutters have been slacking.

Agreed!

We always used the +/- 3mm standard. So technically slabs as thin as 1.05" and as thick as 1.30". If it's under 1" I don't think it passes as acceptable as any standard. That's less than 2.5 CM and closer to 2CM than 3CM!

That is not first grade, it is commercial grade......

We have seen this exact same slab thickness issue, also. If the thinner area is in the center of the slab that couldn't be seen until cutting, then I would think the supplier would back you and replace slab. If it was noticable before cutting, than I feel it is your fault for cutting a slab with noticable issues and good luck with the supplier on this one. I have always told my guys to inspect slabs first as once we cut on them, we have no recourse with the supplier. This is also why your relationship with your suppliers can help you in many ways

I have seen slabs vary nearly 3/16" - 1/4" before. To me it is unacceptable. The worst I've ever seen was 3/4" ming green. The center of the slab was 1/4" thick, but all 4 edges revealed 3/4". But to be honest these problems are far and few between for us. I agree with scott that if you are seeing this very frequently, more than likely these are commercial slabs.

If I'm not mistaken there is even an ASTM standard for thickness variance as well. I'll have to check when I get back to my other PC. I would reject the material if you have time to do so.

What Peter said. The commercial grading does not have to do with processing tolerances. Any good supplier will replace or credit a slab that varies that much.

Just thinking back to some of my customers. I've had customers reject jobs because there was an 1/8" thickness between seamed pieces. It was feathered out but if you looked closely you could see it. I think the customer was unreasonable but tt was sold through a designer so they absorbed part of the cost, we absorbed some and remade it.

If you slab is 2.5 then the supplier needs to eat it. Shame on your guys for cutting it but double-shame on the supplier for selling it. I understand slight variations, but the supplier and the slab producer should have known (and probably did know) that was way under spec. They're not responsible for our fab costs, but I think they're definitely responsible for replacing (or refunding) the slabs. If they don't then find another supplier.

Left side, center, and right side of a 112-inch vanity in Uba Green, a month ago.
Sold as 3cm stone.