Laying Asphalt (Mastic) on an Existing Concrete Slab

[subzero]

We have an existing 1920's concrete floor with no DPM which we need to make damp proof.
The remnants of the original bitumen coating can be seen in places, but most of this came up when the original floorboards were removed (these were nailed into the concrete).

Approx area 49 sqm. So far we've been quoted the following solutions-

1. Excavate the entire floor and replace with new concrete slab with insulation option. £10-12k
2. Lay a 15mm asphalt layer on top of the existing floor. £1k

As we are on a budget, option 2 appears the best solution, although the floor level will be slightly raised. We've seen the finished product in another property and it looks good. Apparently you can lay any type of flooring on top, although have read that wood flooring should not be glued down, and when laying carpet the grippers can't be nailed down for obvious reasons.

It's a big decision so would welcome some advice on this.

 

[dazlight]

Ashpalt is a good solution if not digging up the floor.
How long it lasts can depend on your water table. If your house has a lot of moisture under it it can cause problems in the long run.
I lay over a lot of Ashpalt with karmdean type floors.

Another way is to grind the concrete and then apply a 2 coat liquid DPM then a smoothing compound.

 

[vinn]

Excellent advice above.

Do you have any signs of damp in the walls surrounding the room?

 

[dazlight]

No not that I've seen.
But all depends. If very damp the moisture will find a way.
Is your floor above the outside of your property

 

[vinn]

I dont follow the above reply?

 

[dazlight]

Your ground floor
Is that higher or lower then the outside garden / path

 

[vinn]

I mean: "No not that I've seen."
It suggests that you may have seen the floor? Or I'm getting things confused?

 

[dazlight]

I lay a floor then go. Never had anyone ring me about it.
Can't see it happening though unless you had a waterfall under your house.

When we take up old woodblock floors we get them ashpalted as its a DPM amd builds the height back up

 

[vinn]

No problem but I'm now more confused.
I asked the OP: "Do you have any signs of damp in the walls surrounding the room?"
You replied: "No not that I've seen."

OK, while writing this I see that you thought I was asking you the above question about damp in the walls on your jobs, and replied accordingly.

 

[subzero]

Hi chaps, thanks for the replies and sorry for the delay responding.

To answer the question regarding signs of damp in the walls, at present no but in the wetter weather then yes there are some signs of moisture. We are getting a DPC put in across the entire ground floor as part of the renovation process. This may involve tanking the walls. We have been advised it doesn't matter whether asphalt is laid before or after the DPC installation.

 

[Nige F]

www.masticasphaltcouncil.co.uk They have a list of contractors. Does your quote come from one of their members ?

 

[subzero]

The contractor who quoted us is not listed on that website.