Concrete floor query

[lee666]

After a bit of help/advice regarding my existing concrete floor. Will try and pop some pictures up tomorrow if needed but here's the gist of it:

Our 1900's terrace had the wooden floor replaced with a concrete floor, due to some recent ongoing diy projects it appears that the concrete floor wasn't done right up to the walls. As such I have a couple of questions.

Firstly, would this have been done to possibly allow for any movement/expansion or is it more likely due to shrinkage when it was drying?

Secondly, this gap is filled so it bridges the floor to the wall. It's a very fine, powdery material. Quite dark but not soil if that makes sense, so I do wonder if it's from previous render from the walls or if it was deliberately filled.

We have had issues with the plaster at the bottom of the walls blowing and bulging, and judging by what i've discovered from removing some skirting it appears that the plaster on the walls has been done to the bottom of the floor and in most instances touching this powdery material. I know that doing the plaster down this low is a big no no so I have a plan but would like some advice on if it's the course of action.

Firstly, I plan to remove existing plaster from the floor up to around an inch or so up the wall, and if possible back to the brick.

Secondly, I am looking to remove as much of the material between the floor and wall so there is a bit of a gap. From what I can tell the existing slate DPC is less than an inch lower than the concrete floor so this powder material is potentially bridging the DPC.

Once i've removed the material, would it be ok to leave the gap or could it be filled with something else, and if so what would be suggested. I don't want an issue with cold or moisture coming up from the gap instead.

Sorry for the long post but I'm in the process of removing the skirting in a room that's having wooden flooring put down and I want to do a thorough job to rectify things as well as help the plasterer that would be coming in to repair some damage from the blown plaster.

Cheers

 

[oldbutnotdead]

Some thoughts for you to ponder

Is there any sort of DPM under your concrete floor? (Put some polythene on the floor, weight it down, leave it for a day and if the underside of the polythene is wet then there's no DPM).

Is the floor flat and level and where you want it?

Are there other suspended timber floors that have been deprived of ventilation due to the filling-in of that floor?

While the place is empty you might want to consider chopping a chunk of floor out to confirm/deny the existence of DPC (low odds) and insulation (much much lower odds).

If existing FFL is above the slate course and there's no DPM then now is the time to bite the bullet, break it up, dig down, DPM, insulation, concrete to a level that suits your future floor level plans.

 

[lee666]

Some thoughts for you to ponder

Is there any sort of DPM under your concrete floor? (Put some polythene on the floor, weight it down, leave it for a day and if the underside of the polythene is wet then there's no DPM).

Is the floor flat and level and where you want it?

Are there other suspended timber floors that have been deprived of ventilation due to the filling-in of that floor?

While the place is empty you might want to consider chopping a chunk of floor out to confirm/deny the existence of DPC (low odds) and insulation (much much lower odds).

If existing FFL is above the slate course and there's no DPM then now is the time to bite the bullet, break it up, dig down, DPM, insulation, concrete to a level that suits your future floor level plans.

Thanks for your reply. Answers to your questions are below:

I believe there is a dpc on the floor as when I opened up the fireplace in the same room and had to dig it out I remember seeing blue dpc plastic between the floor and the dirt at the bottom of the fireplace, also, in the hallway where there is a gap between floor and wall I can pop my fingers down and feel what is probably polystyrene type insulation.

Floor appears to be flat and level, not really sure of a way to fully check as I don't have anything long or straight enough to go from one end to the other.

No other suspended floors, the house is a 2 up 2 down with a kitchen/bathroom extension on the back. The living room, dining room and hallway are all concrete flooring.

The house isn't empty so I can't dig a peice of the floor up.

Going by the history of the previous owners bodged DIY work I wouldn't be surprised if the floor wasn't done properly, however I would have hoped that they would have got a company to do it who would do it right.

Any idea if it was proven to be laid incorrectly that I could claim on my insurance? I can imagine it being quite expensive and time consuming to dig up an entire first floor along with the fact that everything would have to go into storage and we'd have to live somewhere else whilst it was being done.

Just out of curiosity, in what order should a concrete floor be laid? I.e if I can feel insulation below the screed, would the dpc for the floor be below that if I were able to check further down?

 

[lee666]

Couple of pics, one is the wall between the kitchen, where you can see the brickwork and above it is a decent render. The brick was covered by the brown, fine material. My guess is that the render line, which runs the length of the wall in a level way, was maybe where the old floor was.

The second picture is of the slate dpc. This is level with the concrete floor. I'm trying to scrape our the material between the wall and floor by the kitchen to see if the dpc is at the same level.

Thete are multiple instances of the wall render touching the floor, so I'm going to chisel this up a bit and back to brick if the render hasn't already perished.

Will try the polythene bit and see what happens. Would a supermarket bag for life be OK to use?

 

[lee666]

Bit of an update as I've spent the last hour or so removing more skirting. I have found more evidence of the floor dpc which is good. Taking off another piece of skirting I found wood between the floor and wall which was rotten.

I've removed a good portion and underneath found blue dpc sheet, can see 2 edges so not sure if it's one piece folded over or 2 sheets.

Would I be correct in assuming that they've laid a hard core foundation, put the dpc sheet on top of that then laid the concrete. Then, using wooden batons they've put down the insulation and screed so that it didn't come up against the walls?

That would explain the gaps, which someone may have removed some of the wood edging, and others they couldn't.

Not sure if this was common practice back then, or even now, but would it be best to leave the gap or fill it with something suitable?

 

[lee666]

I'm after a bit of advice now that I've removed all of my skirting and in the process removed a lot of blown plaster.

As I suspected, all of the walls were plastered down to the floors and then some. As per my previous posts, there is a gap between the concrete floor and the walls which was filled with what I presume was perished render.

I have taken all of this off back to brick to a height that will still be covered my new skirting board, and in doing so allowed the brickwork underneath to dry out. At the time the bricks behind were dark and in the last few weeks have got considerably lighter in colour so I guess they have been drying out.

I now have a conundrum about what to do with the gap between wall and floor as I will shortly be having new flooring put down and I don't know how to go about filling the gap, or if I even should do?

From what I have found, the existing concrete floor has been laid correctly, I haven't been able to see any evidence of my slate dpc, apart on one outside wall so presume it's further down than I can get to so I'm not sure if I should fill the gap with concrete or something else?

My biggest concern would be creating a bridge between the floor and wall so I'm wondering if you can get some kind of pourable plastic that I could pour in and leave to set.

Your advice would be very welcome!