Damn floor levels. Dig up or SLC?

[pilsbury]

My new concrete floor in the extension went down pretty well. In fact couldn’t have hoped for better as a first attempt. It’s 12mm lower than the old floor it adjoins. Done on purpose to allow a bit of tolerance if it all went tits up so SLC could rectify. Could have done it higher in hindsight but that’s the way it is. Just more SLC to add now.

My problem is the old kitchen floor. Removed old 80’s tiles and adhesive to reveal the original square 1.5” thick quarry tiles. The levels are all over the place. Dips in the middle, raised at the edges. Not evenly either. Can be 20mm out in places. Most annoyingly it kicks up at the join between old and new.

The photo shows the rough lie of the land and the green lines show the boundary to the breakfast room which is surprisingly flat and level.

I don’t think I can just wack tonnes of SLC down to fix the lot due to immense cost and it will then screw up the levels into the breakfast room.

Wondering if it’s worth just taking up the quarries and screeding the old floor then SLC the new floor to this? Feels like something I’d rather avoid. Thought groundworks were over.

As you can imagine, I very much doubt a DPM is under these quarries. Should I bang one down if digging up?

 

[pilsbury]

On further investigation it looks like I’ve accidentally poured my concrete slab at precisely the correct level. If I bridge the new concrete floor with the breakfast room floor they are bang on level. What are the chances of that?!

Just the old kitchen floor in between that is out. I’ve mapped the highs and lows as in the diagram below. 0 being the two levels at each end. The majority seems over this. Suggests to me a dig out. At least lifting the old quarries which will lower the lot by 40mm. Then have to build it back up. Suggestions?

 

[^woody^]

Follow the path of least resistance

 

[pilsbury]

Sounds like an old Chinese proverb oh grand master!

With the offending floor higher than the rest, I can’t see an option other than removing the quarries. This then looses 40mm off the floor height giving me between 50mm and 25mm to make back up. I’m thinking dry screed. Is that least resistance? Or is buggering off to the Bahamas and leaving it all behind less resistance?

 

[Footsoldier888]

The path of least resistance must mean you should go to the pub and think about it there!

Perhaps the answer lies in whether this is to be your home for a period of time or not. The guy next door to me has exactly this situation and he went for a 300mm dig down with 100 hardcore, dpm, 100 Kingspan and 100 concrete. Note no sand and the levels are maybe too skinny but he told me he is a builder and has done it a thousand times etc etc.

It took a day to break up the concrete into liftable lumps as it was about 150mm. Then another day to do the earth. Then after compacting he ordered 1 cu metre concrete and used most of it. The space was 2.3 x 3.6. What with the unused concrete he needed a medium skip.

I know the books say 450mm and use sand blinding but I am just passing on what this guy did. Mind you I saw his concrete and it didn't look too clever, some pinholes and didn't look very even!

 

[pilsbury]

Yeah, I could go full bore and take it down a foot and do a proper modern floor make up like the new bit. It will be my home for some time.

But I’m kind of looking for a quick fix this close to the end. If I’d have know at the start I’d have done exactly that. It’s a plastered room now open to the rest of the house. Dust is a PITA. Kind of thinking lifting quarries and going bonded screed route. Possibly the most cost effective which is also important. I’m bled dry.

 

[pilsbury]

Right, on mulling this over I have a plan of action. Bonded screed floor. Let me know your thoughts on the following:

Remove quarry tiles (45mm thick)
Thouroughly clean concrete base
Dilute PVA prime it
Mix a cement slurry as the bonding agent
Slap that on the floor as I progress the screed
4:1 sharp sand cement
30-50mm screed depth
Cover with plastic for a week
Leave to dry for 50 days before tiling.

Advice appreciated as I’m gonna hit the tile removal tomorrow

 

[cdbe]

SBR, not PVA.

 

[pilsbury]

Cheers for the thoughts. Change of plan. Full dig out looking likely. New thread started.