New Flooring – Damp Proof Membrane?

paperclap

Hi all,

We're renovating our first home, a 1955 bungalow.

When first buying the property, the HomeBuyer's Report didn't seem to think the property had a damp proof membrane, under the floor.

Just to save any confusion, I don't mean a damp proof course (running along the bottom of the brickwork).

Under our existing laminate, we have fibreboard underlay (being replaced), along with dark red tiles. I presume these tiles don't contain asbestos?

If they do, may be best to keep them, so as to not to disturb the asbestos. If they don't, is it worth removing?

Anywho, prior to laying new underlay and flooring, is it worth laying a damp proof membrane, or applying a bitumen-based membrane?

Want to do it once and do it right. We've no signs of damp issues. I don't want to find I've introduced this new layer, and find we then have damp issues, due to even more lack of breathability.

Thoughts?

Thanks!

Doozergirl

Doing things like adding damp proof membrane where there isn't a problem could end up causing one. 

I wouldn't put one down if the house has been stood this long and is dry.  

You haven't said what type of flooring you're laying.  

tacpot12

As the property is built in the 1950s it is likely that the tiles are laid on a concrete slab that will be pretty tough and hard to dig out if you wanted to do so. So it is going to be easier to lay a DPM on the tiles, then install some insulation and then a concrete screed on top of that. The floor will be cold without some insulation, and even if it is dry now, with no DPM, it won't necessarily remain so for long. The downside to this approach is that it will raise the levels of the floors by the thickness of the insulation and the screed, digging the existing floor out would avoid this increase in levels. 

The building regs will required at least 50mm of the very best insulation, or more if cheaper insulation is used, and the screed will probably need to be 50mm, so your floor height would increase by at least 100mm. 

stuart45

The majority of houses built after WW2 and before 1965 don't have a DPM.
It does not mean the floor in all of these houses is excessively damp.
It depends on various factors such as the water table etc.
Sometimes asphalt was used as a screed for a DPM.
I think as Doozergirl said, if you don't have a problem leave it. Raising the floor a lot does pose other issues like door frame heights etc.
There is a method where the screed is knocked off, a special thin insulation added and a polymer added thin screed laid to keep round about the same heights, but it does cost.

paperclap

Thanks all.

We'll be laying new underlay and laminate flooring.

Digging out the concrete isn't really an option to be honest. It would cause far too many major issues. Especially if the minimum is 100mm.

I hadn't really anticipated insulating the floor, as presumed a good underlay would do that job.

The underlay I'd planned to use will be foil-backed too, so some sense of a built-in damp proof membrane. But, not sure if these are really true damp proof membranes?

Doozergirl

laurencewhymark said:

Thanks all.

We'll be laying new underlay and laminate flooring.

Digging out the concrete isn't really an option to be honest. It would cause far too many major issues. Especially if the minimum is 100mm.

I hadn't really anticipated insulating the floor, as presumed a good underlay would do that job.

The underlay I'd planned to use will be foil-backed too, so some sense of a built-in damp proof membrane. But, not sure if these are really true damp proof membranes?

It'll be fine.  

plumb1_2

Doozergirl said:

Doing things like adding damp proof membrane where there isn't a problem could end up causing one. 

I wouldn't put one down if the house has been stood this long and is dry.  

You haven't said what type of flooring you're laying.  

Totally agree, plus I bet there’s a layer of asphalt under those tiles

paperclap

Thanks welcome news, thank you.

Makes my life a hell of a lot easier!

Though, pretty sure there is nothing beneath the tiles. I’ve not seen anything. Looks like they’re directly on top of a layer of concrete.