blue layer under concrete floor

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mw96472

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Hi - I've doing some cabling and pipe work in the living room and have dug a channel where the concrete floor meets the wall. I noticed that the concrete sits on a a thin blue layer of light blue paint, a bit like the colour of the walls in swimming pools. The bricks of the wall sits on top a black membrane (I assume that's the damp proof course). The blue layer is on the level just under the membrane. I found some central heating pipes there as well which were surrounded by some black almost sticky layer which sits just on top of the blue layer.

I have a few questions now:
1. What is this blue layer?
2. In a few places the blue layer has been damaged; what can I do to resort it?
3. To feed the pipes/cables from the floor into the wall I would need to dig out some of the blue layer, the sticky layer and in some areas even the black membrane; is this a good idea? what do I need to do to restore the various layers?

Any feedback greatly appreciated :D

Cheers
Michael
 
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Here is an image that shows the blue layer and the black membrane:
living room

living room

blue layer and DPC

And here you can see the black sticky layer that's under the central heating pipes:
living room

living room

blue layer, DPC, and pipe protection
 
Could you post pics of your channel, a larger view of the room and the wall?

Can you indicate what the layers are from, presumably, concrete laid on earth?

eg. earth - membrane "sheet" - bitumen etc. to your finished floor.

Are you certain that the blue stuff is "paint"?

Your skirting is in sand and cement - is this an old property?
 
There is no light in the room so I tried to take some pictures with my camera using its flashlight:

living room

living room

showing channel for radiator pipes along the left wall and channel for speaker cables in facing wall
living room

living room

showing channel for radiator pipes along the left wall and channel for speaker cables in facing wall
living room

living room

showing channel for radiator pipes along the facing wall and channel for speaker cables along...
living room

living room

showing channel for radiator pipes along the facing wall and channel for speaker cables along...
living room

living room

showing channel for radiator pipes along the facing wall including the old radiator pipes
living room

living room

showing channel for radiator pipes along the facing wall including the old radiator pipes

The blue stuff looks like paint as it's a very thin layer and it's stuck to the ground; you can also see some blue on the black membrane which further suggests that it was painted on.

The layers are as follows (from bottom up):
some hard layer (looks like very compacted sand, quite solid)
the blue stuff
concrete floor

where there is a central heating pipe there is some black stuff (probably bitumen) on top of the blue stuff

in the wall, at the level just above the blue stuff is a black membrane (looks a bit like some stiff plastic)

The house was built 1972.
 
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If you do indeed have a sheet membrane (DPM) thats showing at the wall, then where is it in the floor layering?
Maybe the flat membrane is all in bitumen?

I now see that the S&C skirting is merely a camera angle or shadow.

Even in 1972 many BCO's required copper in cement contact to be protected, perhaps that (a protective wrapping) is what appears on your C/H pipes now and again. Or, it could be insulation 1972.

Do you now propose to run channels for new pipework and cables above the in place C/H pipes? Or, are you about to replace the C/H pipework with plastic pipework?

I guess that, essentially, you do have a traditional slab floor but some of the details are a bit confusing to me.

The floor and slab appear dry so i doubt that you've done any damage and can carry on with your plans.


FWIW:
Your wall plaster should stop about 30 - 40mm off the concrete floor surface.
 
Thanks damn09 - there is definitely no membrane under the floor; the membrane is only under the bricks in the wall. Under the floor is just that thin blue layer. The bitumen is just where the pipes were and there was no membrane hidden in there. I assume the blue layer is the DPC under the concrete.
Question therefore is: how should I repair this layer where I damaged it when I was digging out the channels?

My plan is:

a) moving the location of the radiators; this requires extending the existing pipes to the new location; I also want to connect the radiator to the pipes coming out of the wall instead of the floor; they will come out of the wall where you see the T-shaped channel in the wall on the pictures
I will ask a plumber to do that for me.

b) I want to bury some round plastic conduit (not where the c/h pipes are but in various other locations along the walls in the room) so that I can feed speaker cables etc to outlets in the walls
Do I have to do anything special when I bury the conduit?
Or can I just fill the channel with a cement/sand mix?
In what proportions should I mix the cement and sand?
 
The "blue layer" is probably some kind or paintable "damp guard" product.
It certainly looks like it, and you have came to the same conclusion yourself.
The "black almost sticky layer" sounds like it may also be a "damp guard" product, just another manufacturers version of it, laid at the time of laying the central heating pipes perhaps?
A bitumen based product as has been mentioned?
Therefore, would it not be possible to purchase some new stuff (the blue paint stuff, or indeed the bitumen stuff) and overpaint the damaged areas (once any flaking product has been removed and the surface is "sound").
 
mw96472 said:
There is no light in the room so I tried to take some pictures with my camera using its flashlight:

The blue stuff looks like paint as it's a very thin layer and it's stuck to the ground; you can also see some blue on the black membrane which further suggests that it was painted on.

The house was built 1972.
Click to expand...

We started using blue DPM mid 1960s and if that is not a blue poly DPM, then I will eat FMT cat.
Question. How can you paint a DPM on sand?
The black material is either DPC or coat of Bitumen paint on two course of brickwork below DPC to bottom of all internal walls
Patch best you can and wrap all heating pipes in Denso
Regards oldun
 
Looks like it could be swimming pool paint to me. I have known people use it to cover up damp problems before a sale.
 
mw96472 said:
The layers are as follows (from bottom up):
some hard layer (looks like very compacted sand, quite solid)
the blue stuff
concrete floor
Click to expand...

How do you scrumpy boys paint on sand Stu? Got magic brushes?

Keep yer head down and a8se up Stu. Gives you another 200 a day
Regards oldun
 
Thanks everyone - bought some "Damp Proof Membrane Liquid 5L" (http://www.wickes.co.uk/damp-proof-membrane-liquid-5l/invt/241217/) today from Wickes.

Is it a good idea to paint any exposed sides of the walls as well or should I just stick to the floor? It looks like (see pictures in my 2nd post to this thread) the bricks above the PC membrane had been painted in black (possibly a black paint on DPC).

Cheers
Michael
 
mw96472 said:
Is it a good idea to paint any exposed sides of the walls as well or should I just stick to the floor? It looks like (see pictures in my 2nd post to this thread) the bricks above the PC membrane had been painted in black (possibly a black paint on DPC).
Click to expand...
Any comments or suggestions on this please?

Cheers
Michael
 
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