Uneven concrete floor

[eviltoad]

Hi, I've had a look through the past dozen or so pages and can't find anything similar, sorry if I've missed a post.

I've just purchased a 1950's 3bed semi, at some point the previous owners (now deceased) removed the load bearing wall between front and rear rooms, removing the two back to back corner fireplaces in the process.

The flooring looks to be concrete with a black coating of some kind. There are occasional bumps (on average 70mm diameter and rising up to 10mm from surface).

My real concern and focus for this post are two filled in excavation type trenches running from each end of the house towards where the old fireplaces used to be. I am guessing here in thinking they used to have a gas pipe in, but not sure. These are prominent and show signs of efflorescence.

In one particular half of the room the floor has a noticeable rise in the middle particularly around the excavation. The change in height is about 10mm over 1m. There are no signs of cracking, radial or otherwise, however there is a slight change in tone when tapping the floor.

I have heard scare stories about the cost and actions associated with repairing sulphate damage to flooring and hope this wont turn into one of those.

I've included a couple of photos in case that may help.

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• eviltoad
• 2 Apr 2013
• 1

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• eviltoad
• 2 Apr 2013
• 1

Any suggestions or advice would be greatly appreciated as I've reached a standstill and cant consider leveling the floor off until I can find a solution.

Regards

Simon

 

[dazlight]

Can you clean a small bit with water and see if the floor is Ashpalt ?
Looks like it could be which is a dpm too. But it might of had some of it cut into and then filed in.
What are you planing on laying on top?

 

[eviltoad]

Hi Dazlight,

I will give that a go when I get home, how will I tell if it's asphalt other than being black?

My hope is to level the floor and seal it but not sure if I'll need to have the existing floor scraped, old DPM removed from floor and walls and replaced.

Plus I'm a little concerned about the slight hollowness sounds and the 'trench', which I'm hoping hasn't breached the barrier between the concrete slab and the aggregate underneath.

Simon

 

[eviltoad]

Hi Dazlight,

This is how a patch of the floor looks after cleaning it up a bit.

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• eviltoad
• 3 Apr 2013
• 1

I've now pulled all the carpet up so here are the images of the whole room.

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• eviltoad
• 3 Apr 2013
• 1

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• eviltoad
• 3 Apr 2013
• 1

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• eviltoad
• 3 Apr 2013
• 1

I've just looked outside at the walls where the two excavations run to. There are air bricks on the outside walls (filled in). I wonder if they were for providing air flow to the two fireplaces?

Is the slope either side of the excavation too much for self leveling scree to cover up? I've put a 1m spirit level on it for scale.

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• eviltoad
• 3 Apr 2013
• 1

Thanks

Simon

 

[dazlight]

Hi Simon, looks at lot of work to put that right. What you planning to lay on top? Carpet?
If carpet on top that can hide alot an let the floor breath a bit.
To me it looks like Ashpalt but alot of repairs been done as well. If you don't want to dig it up then you could screed and dpm it. Won't be cheap though.
Are you going to live there a long time? More then 5 years.

 

[eviltoad]

Hi,

Yes it would be carpet on a good underlay and plan to be there for a good 10 years min.

The floor is in fairly good condition, on the whole it is reasonably level with just a few 'nodules' . Most of those marks could just be efflorescence and they seem to lift when scrubbed/washed.

It's just where those excavations are that things start to get a bit iffy.

I had an idea after my last post and checked outside. There are air bricks on the outside walls where the trenches hit the walls so maybe they weren't for gas pipe but were air flues for the two fireplaces? There is efflorescence on the them though so either a high water content cement mix or water has got in somewhere.

Any idea how much screeding and dmp might be? rough figure will do.

btw would this whole thing be a job for a flooring specialist or a damp course specialist?

 

[dazlight]

Flooring specialist mate. Where about are you.
Cost is hard to work out mate but to buy the gear approx
Screed £4 per m2
Dpm £5 per m2

 

[eviltoad]

Hi,

Lancashire, well, Greater Manchester actually.

The room is about 24 m2 so the materials are within what I can afford. Might see what a flooring specialist might charge to do the work and what options they may give.

Cheers

Simon

 

[eviltoad]

Hi,

I've had a damp specialist company out (found on mybuilder .com)and one of the things they have suggested is excavation and replacing/rebuilding the floor as they suggest leveling it would leave a 'step' at the edge where it touches the adjoining room and doorway. Also, as there is a noticeable tone difference when tapped in the middle (where it is highest) suggesting it has an air cavity.

They have explained that building control would need to be called in to inspect during and after the works but when I prompted them to see if they would offer an insurance back guarantee they said they would not. This has left me somewhat cautious of them now.

If the works needs doing then fair enough, but could anyone suggest companies or organisations I can approach who may be able to do the work, insurance backed?

Regards

Simon