Ask The Trades - Print Page

Ask The Trades
https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Building Questions >> Cracks in floor https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1632829041 Message started by TrevorP on Sep 28^th, 2021, 12:37pm

Title: Cracks in floor
Post by TrevorP on Sep 28^th, 2021, 12:37pm

More problems, after removing carpet files we found we had ceramic tiles underneath and these had around 6 cracks from wall to wall in. There are no cracks in the walls. I have removed a few tiles and broke out the under floor were a crack was, found that it is about 50 mm thick sand and cement screed on top of a concrete base. The cracks do not appear to go into the concrete. In my onion the s&c screed is very weak and I think it was only the tile adhesive holding it together.
I think that I will have to remove the screed completely and re-lay new floor , unless anyone has a better solution? I thought a 3:1 mix would be stronger. The house was built in early 70s and not even sure if there is a dp membrane under.
Is this the way to go, is my mix ok any help please.
Thanks

[gallery fullsize]TrevorP/1632826176.png[/gallery]

[gallery fullsize]TrevorP/1632826177.png[/gallery]

[gallery fullsize]TrevorP/1632826178.png[/gallery]

Trevor

Title: Re: Cracks in floor
Post by woodsmith on Sep 29^th, 2021, 9:18am

What flooring are you planning to use in this room?

Title: Re: Cracks in floor
Post by TrevorP on Sep 29^th, 2021, 9:36am

Because it is is a type of conservatory/garden room we thought either re-tile or a Karndean type, needs to be mopped regularly with wet dog.
Would it be possible to put some type of insulation down?, my restrictions are height as can only get total including the finish a max of 60mm due to door opening, just a thought!
Trevor

Title: Re: Cracks in floor
Post by woodsmith on Sep 29^th, 2021, 11:44am

Right, you have a few options.

Firstly I don’t think the cracks sound like anything to worry about. No decent tiler would lay tiles directly onto concrete these days as they are so prone to cracking.

I’m just coming up with a few ideas as only you can judge the conditions as you move on with the job.

So, if you want to lay tiles I would recommend using one of the tile backer systems, normally a plastic mesh, but there are other systems. Because of the height issues you will probably have to remove the tiles, then you could possibly use a self levelling compound rather than dig out all the screed before putting the backer down.

If you want to add insulation then you would need to dig out all the screed. If it’s soft it will come up easily with an SDS breaker. If it’s really hard I would go back to previous plan and tile. Once you have the screed out, unless the floor is flat and smooth, level the floor with self levelling screed. Once completely dry use 25mm roofing laths all round the perimeter and lay a few across the room. Fill between with 25mm foil sided insulation boards then lay a damp proof membrane over the whole floor and ideally up behind the skirting. You can then put t&g chipboard, loose layed, on top glueing all the joints and leaving 10mm round the edge. There are different thicknesses of chipboard so you can pick one to give you your required height. This gives you a perfectly flat floor on which to lay a vinyl plank type flooring.

So, if you count a few mm for levelling screed, 25 for insulation, 22 for t&g and 6mm for flooring you are just below your 60mm max.

Hope that helps. I’ve fitted insulation like this on my own home and it makes quite a difference to the comfort levels in the room.

Title: Re: Cracks in floor
Post by TrevorP on Sep 30^th, 2021, 8:58am

Many thanks for a very comprehensive reply, you have given me some good ideas to think about.
I have started removing the tiles and boy they are really stuck down, but what I don’t understand is why the screed cracked so badly, was perhaps because 45mm to thin a screed, and it comes away perfectly from the concrete base, should it have been sealed before laying, or should some kind of reinforcement been added?
At least getting my moneys worth from my sds, thanks for your good advice.

Title: Re: Cracks in floor
Post by woodsmith on Sep 30^th, 2021, 1:44pm

45-50mm is normal thickness for a screed and screeds often crack especially if they dried too quickly. Under most flooring it doesn’t matter but that’s not the case with tiles which is why they have developed various methods of decoupling the tiles from the screed. If it’s coming up really cleanly then that’s a bonus if you want to go down the insulated floor route.

Title: Re: Cracks in floor
Post by TrevorP on Sep 30^th, 2021, 7:08pm

Ok, tiles removed and as screed coming up quite easily we have decided to take your advice and put down insulation as per your comprehensive suggestion. Very difficult to get builders around here at moment, so this looks like a nice diy job over winter.
Thanks for your assistance
Trevor

Title: Re: Cracks in floor
Post by woodsmith on Sep 30^th, 2021, 10:09pm

Best of luck, much better to do it yourself then you know it’s done properly.