What to do about this concrete

[Tomw84]

My flat was built without central heating, and at some point someone decided it'd be a good idea to completely ruin a nice set of floorboards by carving a big concrete monstrosity down the middle of them to carry hot water pipes - pictures attached.

The concrete is in a pretty poor state and protrudes slightly above the floorboards, by about 1mm.

My original plan was to just have floorboards in the hallway, but since I can't do that now my next favourite option would be to lay some engineered wood or laminate flooring over the top. Does anyone know if there's some kind of underlay I could use to mitigate the difference in height between the concrete and the floorboards? If not, then would it have to be some kind of screed over the top of everything?

 

[Tigercubrider]

Thin ply/ MDF.
Halls don’t have as much traffic as you’d think

 

[tell80]

Is the flat on the ground floor?
Are the "hot water pipes" for domestic use or heating?
Whats supporting the pipes, and the thin cover of mortar?
Can you lift a board & have a look below the surface?

 

[Tomw84]

It's on the second floor. The pipes run from the boiler to the radiators.

The floorboards are sat directly on top of a concrete floor slab with joists every 50cm or so, level with the concrete slab. There's no space under the boards.

In the kitchen, the concrete was decayed and I've chipped it away, so you can see what the setup is - picture attached.

 

[Deleted member 174758]

To sort that out I think you need to re-route the pipework along the walls at skirting or ceiling level and concealed behind boxed skirtings, boxing or coving. You don't really want to cut into to that floor without finding out its' composition. For example I once worked on a 1930s library building where the reinforced concrete floors turned out to be just 60mm thick (and I was instructed by the architect to cut holes in the floor to take 70mm deep back boxes... fortunately I realised with the first corner hole ), so if you don't know what the structural floor make-up is then it's best left alone and another solution found, or you could just lay plywood over the top and float a floor on top of that - or even go back to carpet. At least you now know why they reinstated in that way

Take a look at Talon for one ready-made pipe boxing solution (modern, plastic, rectangular - run the cables in Talon clips and their covers clip to the pipe clips) or Pendock plywood pipe boxing. There are other types available, but those are probably the two best known. Of course you can always DIY:

Personally I don't like plasterboard unless it will be tiled over, and in any case MDF seems to paint out an awful lot better than plywood, so that's my go to.

 

[tell80]

J&B offers suggestions - an other suggestion would be:
It would be cheaper to stick with what you've got, esp. if there are no present pipework issues- just remove all crumbling S&C cover and make good with the same.
Lay a flooring with a good quality underlay - wherever you buy the flooring from will have recom underlay.
Be alert to the rise in FFL for doors & thresholds and any transitions.

 

[Nige F]

J&B offers suggestions - :
.

J+B is a whisky . J+K is JobandKnock the pipes need protecting from s/cement. you could use the reflective bubble wrap sold for behind radiators. Stick to soft drinks, tell.

 

[Deleted member 174758]

Cheers!

 

[catlad]

Thick underlay and a good carpet or throw plenty of money at the problem!

 

[dazlight]

Plywood the whole floor with 9mm plywood and glue on the concrete sections. Any loose concrete repair it with a45 ardex rapid repair or similar

 

[Tomw84]

Thanks for the suggestions all.

I'm thinking what I might do is chip away the rest of the old cement, then find some way - probably by hiring a plumber - of making sure the pipes are flush against the concrete floor slab (maybe hold them there by looping something over the top of them and screwing that to one of the wooden floor joists). This would leave the top of the pipes around 5mm below the level of the floorboards. I could then either:

1. Refill the trench with fresh cement, covering the pipes

2. Put wooden supports in the trench

Then cover the whole lot with plywood.

Is there anything about this plan which is likely to go disastrously wrong?

 

[Deleted member 174758]

I'm thinking what I might do is chip away the rest of the old cement, then find some way - probably by hiring a plumber - of making sure the pipes are flush against the concrete floor slab (maybe hold them there by looping something over the top of them and screwing that to one of the wooden floor joists).

Maybe builders band fixed by drilling (7mm), plugging (brown plugs) and screwing (4.5 x 30mm screws) into the concrete sub floor?

Relatively simple DIY job. You can also get the old-style copper pipe clips to do the job as well which are a lot shallower than modern plastic ones (same method of fixing):

 

[Deleted member 174758]

If you take the trench out, how are you going to support the laminate flooring above it? (i.e. how thick is the plywood?)

 

[Tomw84]

Ha! That's exactly the sort of thing I had in mind, but wasn't sure it actually existed - thanks for the links!

I'm slightly reluctant to drill into the concrete subfloor - thought I could screw into the buried joist you can see in the picture attached.

If I refilled the trench with cement once the pipes had been dealt with then that'd support the flooring. The alternative would be to put in a series of wooden supports every 20cm or so. The reason I'm considering the wooden supports option is purely because the previous cement was in such a pitiful state when I took the carpet up (the bit you can see in the photos is nothing compared to the horrendous state the kitchen floor was in!) and I'm worried that'd happen again.

 

[Deleted member 174758]

I'm slightly reluctant to drill into the concrete subfloor - thought I could screw into the buried joist you can see in the picture attached.

If you think about it, that timber is embedded and will be at least 1in (25mm) thick