Setting Out Calibrated tiles

[londonsurf]

Hi

I recently purchased 600x300mm 'calibrated' slate riven tiles. On receipt of the tiles, I note they vary in thickness from 5 to 15mm. My tiler has refused to lay them.

Please can you advise me if there is a British Standard that defines the term 'calibrated tile', and if so what it says. The tile supplier has said to me that calibration does not relate to the thickness of the tile, but its dimensions in plan form i.e. as long as the plan dimension is a consistent 600 x 300, then I have no case. Is this true?

Please help.

[tommyzooom]

Thats not what I would class as calibrated slate, I think the supplier is trying it on

[londonsurf]

They are absolutely shocking tiles - but I need to find the 'legal' definition of a calibrated tile, before I take the supplier to the cleaners!

[Phil Hobson]

I think the true definition of calibrated slate should mean even thickness and size, but I just Googled it and it seems some just calibrate the base of the tile, leaving a riven finish on the top.

That said I have used this type of tile very often, and if you grade your tiles in order of thickness, you can achieve a good result

[Stewart]

Calibrated slate from my store is based on the thickness of the tile....

[Sir Ramic]

Had a similar issue recently where the measurements were the same as your but also the tiles were different sizes. this made the 3 sizes unable to form the correct modular pattern without one joint being 10mm bigger than the others....Client wouldn't accept this of course so they were sent back.

[Bri]

I'd always class the calibration as the thickness.

[peteablard]

As phil says, an experienced tiler should still be able to lay these correctly however extra adhesive will be required!

[Sir Ramic]

I personally think it should be calibrated length, width and thickness. Thats what calibrated means to me.

[deanotile]

are they bad for size other than the thickness? as phil has said they can be fixed to a good standard by grading the tiles and starting with the thicker ones and then working to the thiner ones. *

[londonsurf]

Thank you for all the posts. Slightly confused now. The tiles have a riven finish. Should I be expecting my tiler to sort the tiles by thickness(167 in total) before laying? Isn't this asking too much? I thought the whole purpose of buying calibrated tiles was that they were easy to set out and lay!

I also googled calibrated tile and it seems to relate to tile thickness. The offending tiles are Indian Black Slate 30x60 - Slate - Natural Stone - Tiles

The tiler fitted about 4sqm of tile and then phoned me, said he couldnt work with them, took them up and went home. Tile Giant will give me a full refund on the tiles, but feel like the tiler should be compensated for working half a day with no end result??

[pjc]

calibrated' slate would mean calibrated to thickness riven would be split diamond sawn or chipped edge

[garythetiler]

are the backs ground flat or are they still riven, if they are unmanufactured they are not calibrated in my opinion just "sized" take them back and get your money back

[londonsurf]

Sorry further point - these tiles were £22sqm (reasonable for calibrated tiles). My view is these tiles are 'uncalibrated' as they vary in thickness and plan dimensions. I have been told that uncalibrated tiles are £12sqm. Have I therefore been ripped off?? Wouldn't trading standards have something to say about a uncalibrated tile being sold as a calibrated tile when it is clearly not??! grrrrrrrr

[londonsurf]

the backs of the tiles have a machined ribbed effect running along the length (600mm) of the tile........

[londonsurf]

I note Tile Giant are forum sponsors...may be they can answer the case of their so called calibrated tiles...

[Sir Ramic]

You may have to wait for office hours for that to happen.

[Saltire69]

If it's the sherra slate they can be a bit sizey(is that a word lol). They can be fitted ok though. The calibration on them has change to +-4mm,but of course it can differ quite a bit with it being slate.

[timeless john]

In over 30 years of fixing this natural material I've only ever sent back slate once and that was due to the poor quality and uneven layers in the riven surface.
It's a fantastic product with a unique rustic appearance so if you want perfection rather than aesthetics perhaps go for an alternative lookalike.
In my humble opinion the calibration of the tile is the surface area measurements and due to the nature of the riven surface some variation in the thickness is to be expected.

[londonsurf]

some variation in thickness is to be expected....but from 5mm to 15mm?? How can these possibly be calibrated?

[timeless john]

I'd only be interested in the quality of the surface.
As I said - due to the nature of this product - I don't believe that the calibration term refers to the thickness of the slate, but it may be calibrated from 5-15mm, and on that note I may well be refusing to fix the 5mm tiles.
There have been occasions when tiles have been thick enough to split and get 2 tiles from 1!

[AMtek]

I think the true definition of calibrated slate should mean even thickness and size, but I just Googled it and it seems some just calibrate the base of the tile, leaving a riven finish on the top.

That said I have used this type of tile very often, and if you grade your tiles in order of thickness, you can achieve a good result

as phil said these tiles can still be laid, sort them from thickest to thinnest, lay the thickest tiles first and i normally step up to a 20mm trowel when i cant get 100% coverage with the thinner tiles. its not slate but my pictures of the limestone floor in the "show us your work thread" were calibrated but up to 10mm variance in width, length and thickness and they are all flat with no lippage

[Phil Hobson]

Another thing to consider is joint width, I would recommend 20mm minimum. Any bad lips can be dressed with a chisel, prior to sealing.

I have some pics somwhere, I will try to dig them out

[Daz]

I've done calibrated & uncalibrated slate on floors and walls (now that was a challenge!).
I've found there to be a fair amount of variation where thickness is concerned as everyone has said.
I always use a wider grout joint (as per Phil's post) and I always use a pourable thick bed adhesive for floors.

Daz

[Gall.B]

I note Tile Giant are forum sponsors...may be they can answer the case of their so called calibrated tiles...

Think I may have used the 300x300 of these tiles from what I remember they where a cracking price reflected in the quality tho, not very square and a lot of diffrent widths.

Id be taking the 5mm ones back. If you want better they will cost more.

[Sir Ramic]

Another thing to consider is joint width, I would recommend 20mm minimum. Any bad lips can be dressed with a chisel, prior to sealing.

I have some pics somwhere, I will try to dig them out

My client wanted 3mm joints....or less

[jay]

My client wanted 3mm joints....or less

Has he been told today

[pjc]

In over 30 years of fixing this natural material I've only ever sent back slate once and that was due to the poor quality and uneven layers in the riven surface.
It's a fantastic product with a unique rustic appearance so if you want perfection rather than aesthetics perhaps go for an alternative lookalike.
In my humble opinion the calibration of the tile is the surface area measurements and due to the nature of the riven surface some variation in the thickness is to be expected.

john in thirty years i have never sent any slate back

[impish]

Calibrated refers to uniform thickness. Rectified refers to machine-cut edges with uniform dimensions to tight tolerances.
Riven means riven. You can't have calibrated riven. That's like having a cold cup of hot tea!

You can normally see the marks on the back of the stone where it has been through the machine to calibrate the thickness.
As it's a riven face you can expect variation but it shouldn't be massive. 1-2mm most.

I recently refused to fix some slate from Topps. The brazilian stuff they used to sell was cheap and OKish but now it's coming from India and it is complete and utter cack.

[PHG Wetrooms]

In the case of natural split slate tiles (or sandstone & limestone ) Calibrated is a term used to describe when the tile or paving has had some form of processing carried out to its back face to reduce the variation in thickness caused by it being naturally split, as opposed to sawn/machined.

It cannot give you totally uniform thickness due to the fact that you still have a natural split top surface (otherwise referred to as a riven top surface).

The 'calibration' of the tile could be as little as the use of a sanding disk to take of the worst of the peaks as in typical Indian or Chinese slates (+/-3mm or more!) or a proper machined flat back surface as in a good Brazilian slate (+/- 1mm).

As far as i am aware there is not a controlled standard of what the thickness tolerance should be on these types of material, always check with your supplier before buying and ideally see the variation yourself to avoid nasty suprises.