Replacement Floor + Overlay UFH

[capson]

Hi,

I'm renovating and old (~1870) house. Having pulled up the floor coverings and original (knackered) tiles downstairs, I've discovered that 2 rooms and a sort or corridor area have a solid concrete-like base, although all at different heights, while another room has a suspended timber floor. The concrete seems to be in a decent condition with no serious cracking or evidence of damp coming through. I'm wanting to get all of the floors to the same level and then fit them out with water UFH. I'm thinking of the following:

1. Pull up the old floorboards, insulate between the joists and replace with 18mm chipboard.
2. Paint-on DPM in the concreted areas.
2. Self-levelling compound on the concreted areas to bring them up the the same height as the top of the chipboard.
3. UFH set into 25mm overlay insulation boards throughout.
4. A plywood backing with battens set into the insulation at all edges.
5. Laminate floating on top.

The reason for wanting to use plywood over the UFH/insulation is that I'm hoping to be able to use a reduced thickness. Anything too thick and I'll be getting close to fouling the existing front and back doors which look to be quite new and in good condition. So my questions are:

1. Does the above sound okay?
2. What's the 'thinnest' ply I could get away with for step 4?

Cheers

 

[theprinceofdarkness]

It is less then a mornings work to plane a bit of your two doors, I would ignore this and use 22 mm T&G P5 flooring boards and glue the joints. I think you are very brave or you are doing this to sell the house. Any water leak and you have to lift the whole floor after moving all the downstairs furniture out.
Frank

 

[capson]

Thanks Frank,

Should have said that the doors are uPVC, so a bit difficult to plane anything off them!

I've done the laminate throughout thing in other houses. Luckily never had a problem, but I always figured if there was a leak of something I'd be able to cut into the laminate at a door and just lift one room's worth - obviously that would lose the uniform effect, but better than doing the whole lot.

 

[cjard]

With 25mm of insulation you're going to lose a considerable amount of your UFH heat downwards into the ground.. What scope have you got for smashing the whole lot out, hardcore, dpm, insulation and screeding over UFH? Is this a house for life or for sale?