Sorting an uneven concrete floor

[LarryS.]

So my garage floor has rises and dips all over it of up to 25mm at its extremes in various places, and i want to lay a wooden floor down. I've looked through the forum and as a result I'm thinking the best plan is ....
1. Put a DPC down
2. put battens down
3. level the battens
4. insulate between the battens
5. Put 18mm ply on top
6. Paint the ply

Have I got that right ?

thanks


Paul

 

[MikeG.]

That's one way. Another would be to level the floor with some self leveling compound, or one of the specialist 2 part products specifically for that purpose, then do a floating floor in the normal way.

 

[LarryS.]

That's one way. Another would be to level the floor with some self leveling compound, or one of the specialist 2 part products specifically for that purpose, then do a floating floor in the normal way.

Thanks Mike that’s reassuring, and I’ll do some maths to work out how much compound I’d need, got a feeling it would be a lot !


Paul


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[LarryS.]

So I’ve just used my laser level and found the drop from back to front for the garage is 80mm ! From what I’ve read that’s too much for compound so am I back to the floating floor, with a LOT of shims ?

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[rafezetter]

levelling out 80mm I think you'd be safer just using wedges to level it out temporarily - 2 x 40mm at the thick end, then use full length vertical supports at each intersection - attached to the sides of the beams, not balanced underneath, once levelled. Basically build it as you might a deck, if you are thinking down the road of a full on workbench etc, that will be heavy, plus machines etc, you'll need to consider all of that and I don't think "battens" will be enough.

2 x 2 might be enough if you make sure the beams are about 15 inches on centre in both directions, and put a vertical support at each intersection, with a DPC pad under it.

It sounds like a lot, but if you'll be moving stuff about on wheels and possible bench etc, you'll want the floor as sturdy as you can make it.

If it were I, I would make the base in 3 sections length ways then level up after, trying to do it all at once might prove tricky singlehanded.

 

[LarryS.]

Thanks rafe, sounds like a bit of a mammoth construction but definitely doable, I’m also going to have a look at how thin a slab I could lay too as an alternative


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[stuartpaul]

Paul,

Are you looking for a flat floor or a level floor?

Understand why you'd want a flat floor not so much a level floor. Flat is obviously much easier to achieve and with careful use of self levelling or just battens on existing should be achievable.

If you do want level than you're gonna have to do lots of wedges and levelling to get there.

 

[LarryS.]

Paul,

Are you looking for a flat floor or a level floor?

Understand why you'd want a flat floor not so much a level floor. Flat is obviously much easier to achieve and with careful use of self levelling or just battens on existing should be achievable.

If you do want level than you're gonna have to do lots of wedges and levelling to get there.

That is a very good point I hadn’t even considered, I suppose level is probably a luxury I could do without whereas flat is critical


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[Tervueren]

If you've got sufficient height maybe using firrings front to back and lay timber or chipboard over them would do the job. Only other thing I'd mention is being a garage is the slope deliberate to avoid water ingress ?

 

[LarryS.]

That’s another good point about the water ingress , though without a car ever entering it again that’s probably a non issue now

I’m now minded to try and fill in the dips / cracks for a temporary measure , then later put a dpm down, insulation on top, then 18mm plywood floating floor. Insulation as a bit of future proofing as the rest of the garage is single skin and pitched roof with zero insulation

Would self levelling work for dips and cracks ? I’m guessing not as they’re all on a slope, so what substance do I use to fill them ??

Thanks all for the advice so far is sending me on a far different path to what I’d originally intended, that’s the power /value of the forum for you !


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[Bradshaw Joinery]

A good way to achieve level is with a line laser. If you wanted to screed yourself, or use self levelling, drilling rawl plugs into the floor and setting screws in them every 1' square or so using the laser level to guage their height is a nifty way of getting it pretty damm level. (using a short batten as a guage off the top of the screw to the laser line.) this isnt much use if you need DPM.

if you wanted timber floor, maybe get some lengths of 2x4 CLS and start at the highest point with a 30mm thickness and scribe them into the floor at 400 centres. mark where they sat on the walls, lift them, lay dpm, then put them back down insulate with 25mm and 1" ply on top. (could screw some lath between them to hold in place before ply-ing (is use a laser again here, set the timber off the deck to the line mark the scribe and cut..

Alternatively, Lob some DPM down and get a screed laid over the top. unless its heated a lot, isulating under screed is pretty pointless.

 

[TomGW]

Your garage looks like it's roughly 3.0/3.3m wide and if the slope is a gradual gradient from back to front, while being level, side to side, could you not lay a series of diminishing joists/battens from 130mm down to 50mm across the garage to achieve a level surface? If you start with 130mm at the front and 50mm at the back, with lines between, it should be fairly easy to determine what each subsequent batten needs to be and rip them on a table saw.

 

[LarryS.]

Hi Tom,

I'm thinking of that as a longer term plan but for now the suggestion of going for a flat floor rather than level is very appealing (as it should be a lot quicker / cheaper to achieve).

Plan is to get some self levelling compound, and have a go over the weekend. My only concern is the self levelling may not be the right stuff for small cracks / dips - so does anyone know of a better substance for the job (or a specific type of self levelling compound) ?

thanks

paul

 

[stuartpaul]

Paul,

I've only ever used 'bog standard' (i.e. cheap!) compound but I have played with the consistency to try and stop if flowing too far.

There are some designed for deeper (up to 50 mm) use but I've no idea what that's like.

I think if you use smaller quantities and trowel and/or straight edge it carefully you should be able to achieve a flat floor reasonably easily. Might also be worth filling in stages rather than in one go to give you more of a chance to get it to stay where you want it.

Good luck!

 

[Phill joiner]

I'd give a liquid screed guy a ring in your area. Just fix a 80mm batten along the door end and pump it in. Job done.

 

[LarryS.]

Thanks Phil, I’m going to give the compound a go first, if that’s rubbish then it may be the screed option!


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[AJB Temple]

If you need 80mm why not just float a concrete screed down?

 

[LarryS.]

If you need 80mm why not just float a concrete screed down?

I’ve had a builder in to quote for a new screed floor and it’s an option I’m considering (circa 400 quid). However I’m not sure if I’d prefer a wooden floor to level and be softer at the same time rathe than pouring more concrete

Either way I’ll be waiting til summer to make my mind up as either solution means emptying the garage of its contents for at least a couple of days


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[LarryS.]

Just been out the garage to do some odd jobs and I’ve noticed some of the plywood has lift some sort of spores all over it, is this caused by damp ?
I’d be surprised because the garage has a couple of air bricks so I’d assume that’s enough to stop stagnant air ?

Also spotted some of what looks like damp underneath the side door - the ground outside is at threshold level but the floor inside about 4 inches lower, why would the door area be damp and nowhere else? Could it be a leak through the door that’s most likely ? (The door seems really sound to me)

All of these questions are because I’ve decided to put down a floating floor so I’m wondering the best method ( considering the issues above)

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[LarryS.]

Anyone ?


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