Self Levelling Help - slab split into two?

[Dean A]

Morning all,

I need to prepare my kitchen floor so that it can take tumbled/chipped edge trav and need a little advise.

The area is approximately 5 x 4m2, and the current concrete slab is split into two parts. Each part of the slab was poured at different times (they were previously two separate rooms).

The slabs have been down at least 5 years, so are stable, and were previously screeded with sand/cement which came up with the previous floor tiles. The previous screed was about 50mm-70mm thick (head height is an issue is/was an issue in the room).

There is a 7-10mm different in height between the two slabs, but this varies along the full width of the join (4m wide).

My plan is to screen the whole lot in a single pour of F-Ball Stopgap 300HD SLC, and have calculated that 12 bags should do the job. The slab is quite level, it's just the height difference which will swallow quite a lot of the SLC. There is also a low point in one corner that will need probably 12mm-15mm.

I have taken some pics to try and show you the area, but they are only happy snaps - sorry about the poor quality.

Question is, is my plan to try and fill the area with Stopgap 300 and tile onto this a wise one, should I be concerned about the split in slab under the SLC moving and cracking tiles and finally, from your experience will this take more than 12 bags?

The materials involved are expensive and I want to get this one right.

Thanks in advance for your help :smilewinkgrin:

 

[nybor62]

you will need to prime the floor with stopgap p131
at the depths some of the slc needs to be 12 bags may be cutting it fine imo
you will get 5m2 at 3mm thickness approx

 

[Ajax123]

Repairr that chasm first before you lose a small herd of goats down it and they give you greif for years to come. That crack will reflect through whatp ever you put on top of it if you dont. A low viscosity resin stictch should do the trick.

 

[Dean A]

you will need to prime the floor with stopgap p131
at the depths some of the slc needs to be 12 bags may be cutting it fine imo
you will get 5m2 at 3mm thickness approx

Hmm, I thought it might be cutting it fine, I might increase to 14 bags - this is when it starts to get very expensive at £20 a bag!

I forgot to mention that I will prmie with neat stopgap p131

 

[Dean A]

Repairr that chasm first before you lose a small herd of goats down it and they give you greif for years to come. That crack will reflect through whatp ever you put on top of it if you dont. A low viscosity resin stictch should do the trick.

Thanks for the reply.

The angle of the picture doesn't help, there isn't really a chasm, the two joints butt up against each other. There is just a height differential.

I haven't seen anything about a low viscosity resin stich in my research, is it quite common to use this method? I did consida Ditra matting as I have used this before, but at 20m2 it will add significant cost.

 

[Sean Page]

Have you looked at Mapei Ultraplan Renovation Screed?

 

[Dean A]

Have you looked at Mapei Ultraplan Renovation Screed?

Hi Sean,

No but looks good, and Mapei Eporip sounds like it could do the trick with the join of the two slabs. I used Mapei Fiberplan for the bathroom and it flowed well, do you have experience with the renovation screen product?

 

[Sean Page]

Yes, I've used a fair amount of it and it can be poured to 30mm in one go if needed. I've not used Mapei Eporip before though. I would maybe go for a crack suppression membrane to bridge the join then slc over the top, but it's hard to call from a photo.

 

[Mike]

Is it not possible to have a grout line over the joint and use colour match silicon in the grout line as an expansion joint?

tapatalk on my HTC

 

[Mike]

Oh, and hello Sean, welcome back:thumbup:

tapatalk on my HTC

 

[Dean A]

Is it not possible to have a grout line over the joint and use colour match silicon in the grout line as an expansion joint?

tapatalk on my HTC

Hi Mike,

I am planning on using an opus or french pattern so not ideal!

In addition, there wasn't a split before and the other half won't understand!

 

[Rich]

That looks like a crack and a half. It will need repairing if you are planning to slc over the top of the crack or as Mike has said a movement joint over the top of it.

 

[Diamond Pool Finishers]

you can baulk-up the SLC with aggregate , and have you thought about using an uncoupling -membrane over the joint between the slabs of oversight...

 

[Rich]

How wide is the crack? Im pretty sure that a decoupler will only bridge a gap of 3mm.

 

[Dean A]

That looks like a crack and a half. It will need repairing if you are planning to slc over the top of the crack or as Mike has said a movement joint over the top of it.

Thanks for the reply.

It's not so much a 'crack', it's the join in the 2 substrates. They are stable and about 4-5" thick - just different heights.

There is no gap between the joints, the picture is very deceiving - apologies for the poor quality.

 

[Dean A]

After a few more hours of research, I notice some people suggest using Ditra, but just bridging the crack... this would bring the cost down to a more sensible level, but would this be effective?

 

[Diamond Pool Finishers]

i would say if you repair the crack like grumpy says, then SLC bulked-up to make it go further over the repair, then use ditra/shuluter then tile ......

 

[Dean A]

i would say if you repair the crack like grumpy says, then SLC bulked-up to make it go further over the repair, then use ditra/shuluter then tile ......

ditra/shuluter on the full 20m2 or just over the crack, spanning maybe 1/2 over the crack?

 

[bugs183]

You have to get this baby right, and it will cost, or it will cost you more later if the slabs move.
As everyone says the joint needs to be stitched. Angle grind at 90 degrees and insert threaded stitch bars (i think screwfix sell these, fill with Ecorip. Prime both slabs as said above and cut a 500mm wide strip of Ditra of Dural matting and fix this across the gap with flexible floor tile adhesive. You shouldn't need to use an uncoupling mat on the whole floor.
Level etc as above.
There is a chance the two slabs may move and the combo of stitching and the ditra should do the biz. We've done it between concrete slabs and from concrete onto wood floors, and touchwood we've had no agro.

 

[Diamond Pool Finishers]

i would go for 1/2 m ether side of the crack with uncoupling membrane .
not grumpy but Ajax i was referring to above sorry.....

 

[Ajax123]

Thanks for the reply.

The angle of the picture doesn't help, there isn't really a chasm, the two joints butt up against each other. There is just a height differential.

I haven't seen anything about a low viscosity resin stich in my research, is it quite common to use this method? I did consida Ditra matting as I have used this before, but at 20m2 it will add significant cost.

Resin stitching is a very common method of repairing unstable or fractured screeds.

 

[Dean A]

Thanks for all the advise.

I have taken another close up of the join.

The previous tiled floor was fine for the 3 years we have lived here, it would be sods law that it cracks for me after the laying the new floor!

 

[bugs183]

Yep you can bet it would move now!!!!

 

[Dean A]

I will probably do the lot in uncoupling membrane to be on the safe side, £200 is better spent now than trying to dig up the tiles later to fix

Appreciate all the help chaps!

 

[bugs183]

Not a bad decision. Belt and braces job!
Go to to www.radetiler.co.uk and use the durabase ci matting. Great stuff and a good price, and Dave's a very helpful fella. LAy the mat as above and leave overnight (even if you use fast set), and tile the next day.

 

[bugs183]

sorry it's Tradetiler.com Home

 

[Diamond Pool Finishers]

good -luck Dean

 

[bugs183]

Just reread the thread, Mapei Renovation is the best leveller i've used. Pours nicely, but i've not gone to depths of 30mm, it may take you a few pours over a few days to get it just right.

 

[Ajax123]

You could use a gypsum screed to 30mm but maybe that would just complicate things.....