Can Porcelain floor tiles be laid with a 1mm grout line? And if not what's the reason?

I have a customer that i've told he needs at least 3mm, but he has a builder friend that says he can lay them at 1mm. I thought only rectified stone could be laid at 1mm, but i can't for the life of me think of the reason!?!?!?!
The builder friend has laid Porcelain, in his own house, at 1mm, and didn't seal them, but is having trouble with grout staying in.... Do you get the impression he hasn't removed the coating?

Cheers
Scott

I would always go for 3mm minimum to 5mm grout lines for floors, and Porcelain only needs sealing if the tiles are polished porcelain

Originally Posted by Fekin

I would always go for 3mm minimum to 5mm grout lines for floors, and Porcelain only needs sealing if the tiles are polished porcelain

Yeah cheers Fekin, they are Polished (missed that out of the initial post). I've walked away from this one, even though he's a mate. He's insisted on uni-bonding the screed floor, and gone for a 2mm grout line, so i've left him to it... He's doing the cuts as we speak.

What are the potential problems with grout lines below 3mm?

Originally Posted by beanz

What are the potential problems with grout lines below 3mm?

Anyone!?! It would be handy to be able to explain the why's and wherefor's to customers, or they're going to think i don't know what i'm talking about. Which, as you all know, is true enough; but i don't want them to know that!

The main problem beanz is that tiles are rarely the same size unless you buy very expensive ones. It also depends on the substrate you are tiling on to. Anything with the potential for movement needs to have room for the movement, hence a bigger joint.

To have a 1 mm grout line, you will need to have very high quality tiles, a very stable and flat substrate and very good eyes!

even rectified tiles can vary in size (courtesy of gg in an earlier post) so a wider joint can disguise this. I tend to use 4mm for floors, min 3mm, as floors are prone to movement they need to flex somewhere, if you use flexi grout it can act as a buffer if you're joints aren't to tight

Ah okay, thanks guys!

Originally Posted by doug boardley

even rectified tiles can vary in size (courtesy of gg in an earlier post) so a wider joint can disguise this. I tend to use 4mm for floors, min 3mm, as floors are prone to movement they need to flex somewhere, if you use flexi grout it can act as a buffer if you're joints aren't to tight

Yupp, very true, especially for low to mid end rectified tiles. Did a bathroom with rectified polished porcelain bout 6 months ago, and they cost 50gbp/m2, and they differed up to about 2mm from each other, in the same box. I remember it quite clearly because the customer requested thin joints.

Originally Posted by sWe

Yupp, very true, especially for low to mid end rectified tiles. Did a bathroom with rectified polished porcelain bout 6 months ago, and they cost 50gbp/m2, and they differed up to about 2mm from each other, in the same box. I remember it quite clearly because the customer requested thin joints.

You won't believe this, but my mate has just layed the dreaded B&Q 600mm black/brown Porcs, and he reckons they're spot on! All the same size... I'm going round on Thursday for a nose, as i can't believe it. He's only used 2mm joints, so it could be interesting.

Just to give you an idea beanz mate, I have a brochure here from a company called Atlas Concorde. The produce very high quality rectified porcelain tiles with a tolerance of +/- 0.1%. A very fine tolerance indeed but if you equate that to a 600x600 tile, this gives acceptable deviation of +/- 0.6mm. Doesn't take much to lose you 1mm grout line does it!

Yeah i see what you mean Grumps.

Originally Posted by sWe

Yupp, very true, especially for low to mid end rectified tiles. Did a bathroom with rectified polished porcelain bout 6 months ago, and they cost 50gbp/m2, and they differed up to about 2mm from each other, in the same box. I remember it quite clearly because the customer requested thin joints.

very similar story but with Villeroy Boch tiles (about £80m2) variance of about 2 mm, very annoying as they were on walls also!

Originally Posted by grumpygrouter

The main problem beanz is that tiles are rarely the same size unless you buy very expensive ones. It also depends on the substrate you are tiling on to. Anything with the potential for movement needs to have room for the movement, hence a bigger joint.

To have a 1 mm grout line, you will need to have very high quality tiles, a very stable and flat substrate and very good eyes!

Something like this grumpy

yes, pretty much Whitebeam