Concrete floor Damp proof Course

hueknight1969

Hi Everyone

To cut a long story short we have a concrete floor that slopes! Our builder says he cannot level it because
of the DPC. Yet weve had another builder round who advises he can level it with no problems to the DPC. After all surely as we are simply putting concrete on top of concrete then the original DPC is sufficient I Know this all sounds sketchy but id end up writing a book to explain how we got here but please just ask if you need more info.

Many thanks,:T

Nick

Tucker

Is he not meaning that to level it, it will take the height of your internal floor above the DPC on your external and internal brickwork and thus potentially allow moisture to rise above it?

How old is the house? There may not be a damp proof membrane under the concrete floor itself, just the brickwork, which might be what he's getting at if you increase the floor height.

David_Aldred

Can it be levelled with asphalt which itself will act as a barrier to dampness ? Kindest regards David Aldred Independent damp and timber surveyor

hueknight1969

Tucker think you are right, to be sure im getting someone round from a DPC company to advise us, will let u know how we get on..... many thanks to both of u above, not sure bout the ashpalt option, its on the list of possibles though!

iamcornholio

The DPC (in the walls) is irrelevant to the levelling of the floor ..... ie the floor level can be higher than the DPC

The probelm with trying to level out this type of floor is getting the new screed to either stick down, or feather out. In which case a resin compound may be better - look at the products from companies such as Sika or F Ball.

mikey72

iamcornholio wrote: »

The DPC (in the walls) is irrelevant to the levelling of the floor ..... ie the floor level can be higher than the DPC

The probelm with trying to level out this type of floor is getting the new screed to either stick down, or feather out. In which case a resin compound may be better - look at the products from companies such as Sika or F Ball.

Can only be higher if there is a dpm in the floor.
I had an asphalt one laid to level out an old floor I had, which had no dpm.

hueknight1969

the existing floor is less than 2 years old and has dpm so it looks like im all good thnks to all
you have save me at least 400 pounds!!!!

mikey72

It can still bridge the dpc if it's not done properly though.

iamcornholio

mikey72 wrote: »

Can only be higher if there is a dpm in the floor.

If there is no existing DPM, then there is a potential damp issue already, so raising the floor level above any DPC makes no difference at all

If there was no DPM, then a suface liquid DPM could be laid, and then the new screed/levelling compound laid on that.

Or if the floor has no DPM and no damp history, then no need for a DPM

mikey72

iamcornholio wrote: »

If there is no existing DPM, then there is a potential damp issue already, so raising the floor level above any DPC makes no difference at all

If there was no DPM, then a suface liquid DPM could be laid, and then the new screed/levelling compound laid on that.

Or if the floor has no DPM and no damp history, then no need for a DPM

hmm,

If you have a concrete slab below the level of the dpc in the wall, if you raise it over the dpc you will bridge the dpc in the wall, so allowing damp to get into the wall. If you lay a liquid dpm, you need to cover the walls as well, for the same reason.
If the floor has no dpm, it'll have a damp history.

duncan303

mikey72 wrote: »

hmm,

If you have a concrete slab below the level of the dpc in the wall, if you raise it over the dpc you will bridge the dpc in the wall, so allowing damp to get into the wall. If you lay a liquid dpm, you need to cover the walls as well, for the same reason.
If the floor has no dpm, it'll have a damp history.

I agree.... today I am with a property that simply had the fibre bitumen DPC laid to all wall positions directly on oversite slab. No DPM. Now think on this....... next first-fix timber carcassing and internal plastering and then the screed laid last!.

now thats what I call bridging.........


To the OP Tuckers' answer is on the ball.

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