1st timer on uneven concrete floor

Jock McG · Feb 27, 2017

Hi all. Good forum - been reading it for years.
Now got to 1st major flooring job (9mm floor tiles) on new conservatory concrete floor base of 17m2 and need some advice - trying not to use a leveling screed and build up with adhesive - what do you think?
Sadly when floor was screeded we had a prob and as aresult have a high spot and depression (not just the floor either...).
On the diagram the RED area is the back/house wall and the slurry did not level down during screed (under an overhang) and has give us a high spot area along it's length)
The GREEN area is a depression caused when trying to polish when still wet.
The follr drops from the RED area to the outermost projection at top of GREEN are and at it's lowest point is 10-15mm below rest of area.
Most of surrounding area is 20mm below our finished surface height (we cannot change that) so minus the 9mm for tiles leaves us a good 11mm for adhesive. Problem occours when we get to the depression which then means upto 26mm adhesive to get to level - that area is about 4m2.
Do you suggest anything other than building up with adhesive as I want to avoid if poss using a leveling compound?

WetSaw · Feb 27, 2017

Why do you want to avoid SLC? You'll find it much easier than trying to build up with adhesive and you don't have to worry about exceeding the depth limits of adhesive.

Flintstone · Feb 27, 2017

I would not attempt to sort Those issues out simply by building up adhesive. You will find it very hard to get a nice flat finish and have adequate coverage between the tile and the floor. Use levelling compound, it's made for this exact situation

Flintstone · Feb 27, 2017

If your concerned about your ability to use it, don't be!

Jock McG · Feb 27, 2017

Have used it bofore on smaller areas - biggest concern, other than the size of the space, is overfilling it! The complete base with floor and brickwork are at the same level. The aluminium conservatory is stood on top of that so what you have is essentially a 20mm deep swing pool type space internally. Now that is the absolute max we can build upto including the 9mm tiles! All 3 doors open inwards and if it is overfilled with the slurry then we are b*gger*d as there will be no room for tiles/adhesive. Even more complicated by the fact that the high spot is the red zone for the house wall and the low spot is the furthest away so by the time you have poured the slurry to suit the red high spot it could be too little or too much! The margin for error is zero.
Does that make sense?

WetSaw · Feb 27, 2017

According to your drawing you have a "pool" . Just level that area if you are worried about the overall level getting too high. You may just have to accept that the floor is flat not level if there's no height to play with by the house.

LM · Feb 27, 2017

Couldn't you take the red area down with a grinding cup then fill up the green area to meet the new reduced height?

Flintstone · Feb 27, 2017

You don't really need to be level, just flat

Jock McG · Mar 2, 2017

The Red area will need to be ground 5.5mts x 4-500mm wide and come down is spots about 10mm but sems as thoug it's goint to be the only way - helluva mess inside a new glass build though!
Decided in meantime to put some levelling compound on the majority area - got Mapei for the job.
Any suggestions for a good runny mix from the experts? Mapei say use only 4.5lts/25kgs - sounds very dry mix and this being winter temps inside theis 17m2 x 2mt high floor to glass unit are understandably chilly when the sun drops.

WetSaw · Mar 2, 2017

Mix to the manufacturers specification, do not add more than the maximum amount of water specified. You'll be surprised how runny it is!

LM · Mar 2, 2017

Jock McG said:
The Red area will need to be ground 5.5mts x 4-500mm wide and come down is spots about 10mm but sems as thoug it's goint to be the only way - helluva mess inside a new glass build though!
Decided in meantime to put some levelling compound on the majority area - got Mapei for the job.
Any suggestions for a good runny mix from the experts? Mapei say use only 4.5lts/25kgs - sounds very dry mix and this being winter temps inside theis 17m2 x 2mt high floor to glass unit are understandably chilly when the sun drops.

Hire a dustless system for the job, it'll be worth it or buy a shrowed attachment for a vacuum.

Jock McG · Mar 3, 2017

All good sound advise - cheers.
Final (hopefully!) question - as per attached picture I will be using 300mm x 10mm mosaic tiles for edging and as you can see the cut angle is going to be 11.25 deg (I have to cut 18 of them) - anyone got tips on best way to cut with a wet table top saw?

LM · Mar 3, 2017

Jock McG said:
All good sound advise - cheers.
Final (hopefully!) question - as per attached picture I will be using 300mm x 10mm mosaic tiles for edging and as you can see the cut angle is going to be 11.25 deg (I have to cut 18 of them) - anyone got tips on best way to cut with a wet table top saw?

Fashion a guide from plywood or cementboard at the required angle to rest your tile on and position it on the main bar and simply push through the cutting wheel or pull the blade over which ever the case.

stuey72 · Mar 4, 2017

Similar job few months the back.

Tented entire area off, and ground down high spots with diamond cup wheel on a 4-1/2 grinder. Prepare for zero visibility and a shitstorm of dust on epic Sahara desert proportions. Looked like an earthquake survivor after 3 hours of grinding and a burnt out Makita grinder as a souvenir.

Hire a professional grinder and extract system.

Jock McG · Mar 11, 2017

Update: Used the Mapei self levelling and got 10m2 for 3 bags - did'nt realise floor was so far out!
Now setting tiles in - started with Topps Tiles slow set adhesive - anyone used it before?
Mix says 4kgs to 1 lit water - that mix is like treacle! Torturous to mix and even with the floor level brought up we got only 8 tiles for 12kgs adhesive (not inc water) and thats using a 20x10 round notch trowel and back buttering tiles to get to level. Anyone used it before with a thinner dilution? It's like pushing cold toffee around!

Flintstone · Mar 11, 2017

That trowel will eat adhesive I think. I don't think any regular s1 rated adhesive should be that thick! Ratio sounds right tho.

Jock McG · Mar 11, 2017

Sadly have to use that much to get level with the sole plate - as we get nearer house wall it will go down to 6mm notch - just a bugger to try and mix - will not even try using the drill to do it! Have been doing first couple mixes at 4kgs only till we get a good level then can crack on bit faster - but even mixing 4kgs/1 water is tough!

Flintstone · Mar 11, 2017

What size are the tiles ?

Jock McG · Mar 24, 2017

Not gone away folks - just very busy.
Tile size is 298/499/9mm - approx 190 of them
Lets give you a few stats and a laugh - sadly I'm not!:
To get to height required to reach sill plate each and every tiles nes to be bedded in and leveled - just like slabs. So whats to problem??? Welllll......each bag of 20kg (fast set) adhesive (tiles backbuttered) is working out to.... 9.3 tiles/bag (2.15kgs/tile) - YES 9.3 per BAG! Wasteage is around 2.3kgs/bag. Max I'm trying to lay at a time is approx six to allow to set - so progress is frustrating to say the least. The cost is - mind blowing considering tiles were £1.00 each - adhesive is costing more. Used 4 different types so far: Topps white but was cream (slow set £15/bag Trade but at 4 days drying!) Topps fast set white but again was cream @ £18/20kg, Unibond grey (Screwfix £11 - but they only had 3) ,Just managed to find Tradepoint fast grey at £24/60kgs but they only do in grey - why is it so bloody expensive and difficult to find white? So far the cost of adhesive is about £1.79/tile.....now going down to £0.86. However when setting the edge cuts and mosaics will have to go back to white and prob have to buy on line as no local suppliers do and decent prices on white.
Now the last fact: time to set a tile. Well from setting up/mixing/prep/laying/cleaning it's working out around 22 mins a tile and after a pityfull 81 set so far (albeit they look almost perfect) thats a wage shattering 30hours! Don't see how it can be done any faster and keep the stardard this high. God help me when it gets to the custs/mosaic......
So thats some scarey facts to gas about with your fellow tradesmen folks.