Kitchen floor concrete but dips

I take it this is a solid concrete floor and not a 'suspended' type?

Is it the original floor? (Sometimes suspended timber floors were filled in and replaced by concrete when rot or damp issues were found).

Are there any cracks in the floor - the concrete slab?

It could be subsidence (minor - ie chust in the slab itself) or it could have been a poor job in the first place.

If the former, I'd expect the slab to be cracked - it's hard for concrete to sink in the middle of a slab without breaking up!

 

If you need to level the floor, then use the product made for the job - this is superb stuff;

http://www.screwfix.com/p/mapei-ult...kg/4959f#product_additional_details_container

You cant really level a floor with concrete anyway. Closest thing would be a cement screed but then you have limitations on minimum thickness (may be around 20mm but I'm guessing) and you cant feather out the edges

As long as the existing floor isn't actually collapsing and is sound, although uneven, use the levelling compound. Will need to seal the existing concrete first using an SBR primer then away you go - whilst primer is tacky. Very easy to use, minimal prep, maximum pour in one go is 40mm, additional layers can be added if more depth required, you will be impressed for sure

More than likely the original floor is just uneven from the initial pour - good luck

 

I'm guessing that the kitchen would have had a suspended timber floor originally too, tho' there's a chance it was always concrete - perhaps to handle the weight of a solid fuel cooker or summat.

Anyhoo, what to do? Well I suspect it does come down to the state of the existing floor - eg if it was poorly done with a thin concrete slab and poorly packed substrate, then there's a chance it's still 'moving' so levelling it off might result in future cracks. I don't know.

However, if it is nicely solid and free from settlement movement cracks - ie it was just a poor, unlevel, job - then it should be fine with levelling.

I don't know what to recommend - I'm not a builder.

I guess what I would do in your position is to lift the vinyl to expose the concrete, and if I felt confident it was all pretty darned solid and unlikely to move any further, then I'd lay a DPM (to be certain of blocking rising damp) and screed on top with a suitable self-levelling compound.

Not sure what sort of DPM to recommend - plastic sheet or 'chemical' (like tanking slurry) - or the best levelling stuff.

You say it's sloping at around 5 to 8 degrees? How much lower is the floor at the centre - an inch or so?

 

I've got a similar issue at my 1950's gaff, the concrete lounge floor slab has settled over time and its down may be an inch or two in one corner. There are no cracks as far as I can tell and its not moving any more, so I'll likely use levelling compound to bring it up level.

In your situation, you need to establish just what's going on; whether it is a fully concrete slab, whether its stable or is cracked and still subject to movement. The out come of that will determine what's best. If its cracked or still moving, it will need to be fixed properly or the slab removed and relaid. As the rest of the house is timber floor, I wonder if the kitchen timber floor was ripped out and this concrete slab laid poorly.

 

Regardless of whether a DPM was fitted when that slab was laid, you'd be nuts to not add your own at this stage.

The problem with damp coming through a concrete slab is that, once you have fitted a floor covering, any moisture coming up can't evaporate so instead sits there damp and mouldy and smelly and 'orrible.

Are you planning to remove the vinyl anyway? Hopefully you are - so then we'll have a better idea what we're dealing with.

If the slab has numerous cracks - suggesting it has sunk in t'middle but not so much at the sides - then I wouldn't consider that an unstable surface and likely to cause ongoing issues. Any DPM that was added when that slab was laid is also likely to have been breached in numerous places due to the movement.

 

Yep, sweep floor to remove surface dust and debris, doesn't need to be totally dust free as the SBR will seal and bind the dust, but get the worst off 1st

SBR looks like PVA, i.e., thick white gloopy glue looking stuff - more expensive but importantly didn't be tempted to use PVA - totally wrong product

Wickes sell a self levelling primer or S Fix and others sell SBR - just follow manufacturers instructions. Basically it's diluted as per instructions and brush on, allow to go tacky then poor levelling compound

Loads of previous posts on here re using self levelling compounds, have a read up but generally easy to use. Some require some trowelling to help level, some level by themselves - more or less. But yes, I'm diy also and this is a job you can do yourself

Buy a large plastic 'trug' (think they're called, like a large bucket used for garden waste and general building) and a cheap mixing paddle that will fit your electric drill. These items make mixing the compound a doddle (again follow M I)

When you say vinyl floor, is this vinyl tiles stuck down or vinyl sheet / Lino ?

 

We'll know more when that flooring is removed.

Are they flexible vinyl 'planks', or rigid laminate?

Since the damp is at the lowest point, the cause could be anything - a washing machine leak would end up there, for example.

 

One you should have primed concrete floor prior to lay the compound,with SBR diluted with water up to 3 to 1 depending on how porous the floor is, or use a primer, like the Setcrete primer.

 

It will prob dry out. Is the room heated?

 

What flooring are you planning to put down?