Shrinking grout

[Ookysoft]

I tiled 2 walls on plasterboard on Wednesday - grouted today [ Saturday ].

Used Dunlop Waterproof ready-mix - supplied to me to use.

As it's drying, I can see it shrinking - 'V' shape into the lines and some cracking.

Am I in error here?

I normally mix my own grout a little wetter than this stuff. The room was temperate [ ie I needed a T & Long sleeved shirt ]. The tiles are 250 x 330 ceramic - applied with Bal Grip.

Have I to scrape it all out or just re-grout over the top, as it's an epoxy I assume it'll stick like the proverbial?

Thanks

 

[Richard C]

Dunlop is owned by BAL whose products I know & use exclusively but I’m unsure if they are identical or even similar so am not really familiar with Dunlop products; you say it’s an epoxy but why? What exactly did you use?

You should really be using a powder cement addy with tiles that size/weight (but gypsum must be primed first) &, personally, I would not use addy/grout products supplied to me unless I was 100% happy with them!

 

[Ookysoft]

Sorry - I assume it's an epoxy product, as it's branded as a pre-mix waterproof product, as opposed to a water resistant product.

 

[Richard C]

Most adhesive manufacturers use the term “waterproof” rather loosely although some do elaborate more in their data sheets. What it generally means is that the adhesive/grout is waterproof in the sense it won’t dissolve when exposed/immersed in water, it’s not impervious & will still absorb water which is why it’s important to have the correct tile base. Exceptions are rather expensive epoxy products which you seem to have picked up on but true waterproof epoxies are usually a two part mix. I’ve looked at the Dunlop stuff & they only make one redimix grout so pretty safe to assume that’s what you have. Unfortunately neither their data or COSH sheets state what it is but as it’s only single part, pretty safe to assume it’s not an epoxy.

Why has it shrunk back; apart from possible problems with adhesion on large format tiles, tub mix will take far longer to dry out before you can grout as it relies on evaporation to cure rather than the chemical cure of cement powder addy. Two days may not have been long enough & it could be there was still excess moisture in the adhesive when you grouted as shrinkage tends to happen when it’s overly wet. Did you ensure it was forced well into the grout lines? Was there excess adhesive filling the grout lines?

Getting good adhesion between the two will be the problem with just going over the top again once its set & unless you rake out again, it’s likely to start to flake off before too long.

 

[Ookysoft]

Though I appreciate that the adhesive in the centre of the tiles may still have been setting, poking around the edged seemed set - the lines were pretty much clear & I picked out the few areas of concern. The idea being the grout jointed between the full tile edge to tile edge. Yes, it was well pushed in - to the point that their 8M estimate for 150mm sq tile coverage [ I think ] ended up being approx 4M when I'd wedged in as much as I could, between these larger tiles.

Too much used, do you think?

I'm rather hoping, as they clearly market it as waterproof [ whereas I see their powdered microban stuff is marketed as water resistant, that it is.

I over-coated the shrinkage and advised that I'd come and re-do it if there was an issue. Lucky it's supplied product. Last time I used pre-mix, it was Evo-stick and it did exactly the same thing.

Thank you for your input here.

 

[Richard C]

Thank you for your input here.

You’re welcome. Tip for the future is that quality really does matter & with the correct preparation & materials will give you the consistency necessary for trade work. Not cheap but for me it’s BAL or nothing; I know there are other products just as good but it’s what I’m used to working with that matters for me

 

[gcol]

Pre-mixed shrinks, powdered doesn't.

 

[Ookysoft]

Thanks! That's become very apparent as I did 2 walls with powdered.

Kinda thinking the adhesive and wall sucked too much moisture out of the pre-mix.

Lesson learned for me - keep away from re-mix [ which I feel is less manageable anyway ]

 

[Richard C]

Pre-mixed shrinks, powdered doesn't.

Merry chrissy gcol; does the Messiah return or did too much brandy in that pud sauce cause an error

 

[Jasonb]

Its probably the depth of the joint or even the width (you don't say what gap). Large format tiles tend to be 8-10mm thick and the premixed can't cope with that, it may be OK on 150x150 thin tiles eg about 4mm but after that it will shrink.

Jason

 

[Ookysoft]

Hmmm!

3mm gap, 6mm [I think, or maybe 7mm] tile on a 6mm notched adhesive [ so another couple of mm when that's dried back, assuming I squished it flat ].

I'm just going to steer clear of the damn stuff.

Thank you!

 

[jctilingservices]

going by the size of your grout line gap, you should have used " wide joint grout"

 

[Ookysoft]

Tub says it'll be fine for 4mm so given my 3mm is 25% less.... ya kinda hope it'll cope! Though my previous coverage statement does suggest it doesn't do what it says on the tin!

 

[Richard C]

it doesn't do what it says on the tin!

I think youve got the jest of it ; my moral is only put your trust in quality products which you know will behave as you expect, even if they are expensive, it’s still an awful lot cheaper than having a failure which you then have to put right at your own expense. If you had the product forced on you then you could argue it’s not your fault & walk away but I would have made my feelings clear right from the very start!

I think JCT misunderstood your grout line thickness

4mm is wide joint territory IMO but you should have been OK with a 3mm grout line. I don’t think your problem was just about the grout you used; as myself, others & god

have said, your problems really started when you used a tub mix addy/grout instead of powder mix on that size of tile.

 

[jctilingservices]

I think JCT misunderstood your grout line thickness

quote]

you are correct Richard mate, i think i got confused when he brought up 6mm alongside 3mm, i assumed he had a 6mm joint