Floor Problem

[Mark A]

Hi chaps,

I have a little problem with a wobbly floor.

The old screed is awful (cracked and undulating) and the difference between the peaks and troughs is 20mm or so in some places. It's also not level.

Plan A was to grind off the high spots and fill in the low spots with something like tile adhesive. Yesterday I had a go at grinding a section and it turns out the screed is actually just a 1/4" thick crust over rough concrete. Over to Plan B.

What is Plan B?

I refuse to take up the floor and lay a new screed as I don't have the time for such drastic work.

Self levelling compound is not an option either, as the existing floor is neither level or flat, so it would raise the floor up more than I'd like. And to cover 38sqm at depths up to 20mm will cost far too much. And I'm crap at laying the stuff.

Any suggestions?

Cheers,
Mark

 

[MattRoberts]

A buddy of mine has laid chipboard loft flooring in his garage, and it's worked a treat.tongue and groove, so easy to lay

 

[pcb1962]

I have no experience with this, but I would think about hiring a concrete grinder machine

 

[Mark A]

I have no experience with this, but I would think about hiring a concrete grinder machine

I already have a setup like this https://www.sunrisetools.co.uk/dust-control/grinding-sanding/g-tec/180mm-g-tec-grinding-system.html which would otherwise have worked well, it it didn't rip up the thin crappy excuse for a screed.

 

[Phil Pascoe]

What is the "room" used for? - obviously something suitable for kitchen isn't necessarily any use for a garage.

 

[Mark A]

Initially just the living room. The other rooms directly connected will be tiled so any discrepancies at the threshold can be accounted for with more or less adhesive.

We're not aiming for a level floor, just flat enough for oak flooring - the house has subsided a few inches at some time between the late 1700s and 1979 when one of the extensions was built on (badly), so in one direction no surfaces are perfectly plumb or level.

 

[Phil Pascoe]

Any dpc's anywhere?

 

[LancsRick]

I might be misunderstanding your post, but you seem to be trying a physical impossibility?

You've got an uneven surface, which you don't want to reduce in level because you don't want to reshape concrete, and you don't want to raise in level. You've got to do one of them to achieve levelling, or am I missing something here?

 

[Mark A]

I would have been happy to grind down the high spots, but underneath the thin layer of cement screed is loose, rough concrete and I really don't want to open a can of worms if that starts to break up.

Raising the levels a bit can't be avoided, but how?

I think self levelling compound is out, as it it will take a lot to level the whole floor. I'd prefer to just flatten the floor with something, but keep the existing small slope, rather than level completely.

 

[Mark A]

No DPC's in the walls as they're stone. The internal walls have been lime-rendered to allow them to breathe, the external walls will be done late Spring/early Summer (if I can get round to doing it).

 

[Dee J]

Given that starting point... and you're going to the expense of oak flooring...

The ideal solution would be dig out and replace to a decent spec with dpc, insulation, screed etc.

A work around could be to lay battens at 400mm intervals... probably over a dpc. Screw and plug the battens to the floor which shims and spacers to level up. Then lay the oak floorboards on the battens and slant nail through the tongues.

Or the horrible bodge method: slather the old floor in dilute pva, patch in up with sand-cement mortar. Then lay the oak as a floating floor and hope it sags enough to follow the undulations.

Good luck

 

[Mark A]

The floor does have a membrane already and it is effective as there's no damp coming through.

I've considered battens but it's going to raise the floor up a fair bit...

18mm flooring + 18/25mm battens = 36/43mm at the highest point, probably more than 56/63mm at the lowest.

I'm concerned about the doorways as there won't be a lot of clearance if I went down the batten route.

 

[HappyHacker]

Won't the grinder take off the high spots off the concrete? Otherwise you will have to increase the level to the highest spot.

Then get a plasterer to lay a new screed or floor levelling compound, I can't lay the stuff either. The floor levelling compound would be a better bet as you can lay a thiner layer.

 

[n0legs]

Use the Ardex levelling system and use the fine chippings to bulk out the compound. It'll go to quite a thickness with these added and can obviously be feathered out.

http://www.ardex.co.uk/products/categor ... -compounds

http://www.ardex.co.uk/products/ardex-aggregates

I've used this quite a bit over the years. In the one place 1" thick feathered out to nothing.
Get a spiked roller to lay it.