Insulate over existing concrete floor

[nimzv]

Hi I have a two bed purpose built ground floor flat, mid 60's construction.
Decided to rennovate and move in after my last tennants left.

The entire floor is concrete, and in most areas the original lino is still on and refuses to come off!

After much debate I decided against installing UFH, and will stick with radiators.

I had previously installed cork tiles and then laminate flooring over, but as I was not living in the property I really don't know how warm/cold the floor would have been but my tennants did say that it was always pretty cold all year round.

Basically my question is what would be the easiest and best solution to put down on top of this concrete floor before I put down my new lino to provide some insulation from the cold concrete floor below?

I have a decent ceiling height 2460mm, so I have no problem raising the FFL by 40-60mm.

A friend of mine mentioned that I should first put down some DPM folding over and taping at the joints and also leaving 100mm around the perimeter of the room, he then said I should put in Kingspan K3 boards, and then put my lino on top.

I am unsure as the information I found about that product indicates that you must screed over it, also the cost per sheet is out of my budget.

Another suggestion was to again place the dpm down first and then cover over with 40mm thick polystyrene sheets, and then either a layer of chipboard or plywood before having the latex and lino.

I like this idea but am not sure if it is a viable solution and would appreciate some advice.

As I am also having all new electrics and plumbing being installed, I thought I might be able to save myself the hassle of cutting floor channels for the pipes and cables into the concrete floor, as by putting down this 40mm polystyrene I could run all the services on the existing floor and then they would get covered over with the ply or chipboard, and then all I have to do is chase the walls and ceilings for the electrics, whereas the radiator pipes can just come straight up through the new build up of floor.

Again does this sound like a viable plan?

Untitled

• nimzv
• 25 Nov 2013
• 1

Untitled

• nimzv
• 25 Nov 2013
• 1

 

[Architexeter]

I'd go for a DPM, insulation and chipboard floor. The chipboard floor should be a good high density board as Eggerboard or similar. Now the insulation, there are loads of options but generally the thicker and more expensive the better. I have used rigid boards as Celotex/Kingspan/Ecotherm and used 50mm boards. Polystyrene is cheaper but not as insulating. Current regs are about 80-100mm of Celotex etc so you fall short but will see a huge improvement. In theory under the latest building regulations if you touch more than 25% of an element you are meant to upgrade the insuation to current standards but it has to be practically possible to do so.

Something is better than nothing.

 

[nimzv]

Thanks for your advice, I was already looking at celotex rigid boards so you have given me some confidence to pursue that route.

The chipboard I was going to use would be 18mm MR T&G, do you think standard egger chipboard 8 x 4 sheets could be used just aswell?
If so that would work out a damn sight cheaper.

 

[Architexeter]

I used MR but then I had a lot of wet rot, dry rot and woodworm in my property so just wanted to be sure, I would defo go for MR in kitchen and bathroom if you are doing these areas. Other areas are your call and subject to the soundness of your building, to be honest - any defects would probably take many years to show anyway. For example, in my property the sub floor ventilation was blocked by a 1937 extension and dilapidation took until the 90s to show.

If its really a cost driven exercise then I'd say MR throughout is overspec.

 

[Blagard]

Your mid 60's floor should already have a DPM so another seems pointless unless you have damp issues. Toss down some cheap insulation, say 25mm polystyrene and lay 18mm chipboard floor over with joints in the chipboard glued to give you a floating floor.

Note all your doors will require quite a bit chopping off the bottom and maybe not all will let you without having to insert new timber, if hollow cored.

You may need to refit skirtings and cut back architraves for best effect. Don't skimp on the external door details as the thresholds will need raising. If using a laminate refit skirtings afterwards to avoid quadrant - urgh!

Personally I would search for "warm" type of floor finish and carpets with a quality underlay. I think most hard finishes have a cold feel.

 

[nimzv]

Thanks For the Advice

The property has suffered from Damp in the past, as the old timber framed windows were letting water in.

I have since replaced and treated all mould and will be putting in appropriate vents in each room this weekend

It seems that all the ground floor flats within the development suffer from condensation and mould which makes me wonder how well the slab is insulated.

If I forego the DPM before I put down my insulation should I still put a Vapour barrier between the insulation and the chipboard floor?

 

[Newboy]

Appreciate the reason for doing this but I suspect that if you're raising the internal floor level by 60mm you're going to create a few problems - height through doorways being the most obvious - anybody at 6'2" or above is going to have a close shave getting through!

Also the entrance door is going to be a bit strange with a 60mm step up into the flat from the (presumed) common hallway + the front door to the flat is going to look a bit strange with a 60mm cut-off - might be worth checking fire regs aren't compromised

 

[nimzv]

At the moment FL to CL height is 2460, so the I can live with losing 60mm.

I have a small bespoke joinery so will be changing all the door sets including main entrance, raising the floor level isn't an issue.

As it is at the moment when entering the front door the threshold is already 90mm higher than the floor level in the flat so currently you step down into the flat.

Should I be putting a barrier between the insulation and the chipboard floor if I am not putting a DPM under the insulation?