Insulating & UFH onto solid concrete floor.

[Andehh]

We are renovating an old property up north, that has a cellar and solid brick/concrete floors onto floorboards/joists in part. These are uninsulated, but in good and level condition.

We can't dig down due to the cellar and solid concrete/brick floor built on top of it, but we desperately need to install some insulation. We also want wet UFH throughout.

We can afford to loose around 60-100mm of floor height throughout (absolute max) , so am hoping to see what you guys would advise as a way of achieving insulation & UFH.

1) celotex adhered down to concrete, with/without grooves for pipe, then a low profile screed over the top for kitchen with tiles.

2) celotex adhered down to concrete with grooves for pipes, then plywood adhered to the top for carpeted and engineered wood floors

3) celotex adhered down, then this (or similar) laid over the top http://warm-board.com/warm-board/

Many Thanks in advance

 

[dilalio]

Explain existing floor in more detail... Is some of it concrete and some suspended? Are joists sitting on concrete? Hard to picture what you have from your description!

 

[Andehh]

Sorry, for not being clearer. The lounge is a simple suspended floorn(floor boards on joists) which we can mostly access above and below. Not too worried about this, as we have all options open. Just worried about the weight of screed on the joists, but trusting the builder on this.

Dining room/kitchen and hallway is less easy, as the cellar below is a mixture of stubby tunnels and small brick rooms. Most of the ceiling of the cellar on this half of the house is bricked arch ceilings and some crawl ways which reveal joists /floors boards which look to have been concreted on and then tiled in the rooms above.

Hence looking to see if I can get away with leaving floors as is and building right on top or the existing floor surfaces and accepting the 3-4" height build up.

Edit;

After a few more hours of research I am running out of confidence on "guranteed" overlay solutions that will do the job vs biting the bullet, ripping it all out to bare joists and starting again. Ripping it all out would also allow us to inspect existing joists and foundations.

Anyone able to comment on any of the above ideas?

 

[dilalio]

Well, raising your floor levels throughout comes with knock on effect for doors, windows, waste outlets etc!
On suspended floors it's normally done by underbattening 90 degrees to the joist, struts to floor where necessary on long spans, put old boards back down onto battens, between joists and thickest insulation you can get that will allow at least 70mm of screed over the top. Don't worry about grooved board, just clip pipe to the celotex or use nail clips with screws through the celotex into the old floor boards below, to hold pipe down. You shouldn't need to stick celotex down as weight of screed will keep that in situ.
To maintain levels of solid floor to meet with suspended then may be best to break out old concrete between joists and rescreed with heating pipes below...

 

[Andehh]

Thanks very much dilaio, why is the need for such thick screed?

Due to where the house is and distance from the ''lane'' that runs through the village we'd never get a mixing truck/large appliances on site to pump large amounts of screed in. Could we get away with a thinner build up of screed, as I imagine much of it will need to be mixed and poured on site?

 

[mointainwalker]

Where possible insulate below the floor as this gives multiple advantages:

1) Minimises loss of height in living areas.
2) Allows use of much cheaper mineral-wool insulation
3) Fixing pipes to wooden floor is much easier than into plastic insulation.

There is no difference to heat-loss insulating above or below the floor.


From memory liquid screeds require a minimum of 40 mm thickness ( 20 mm on top of pipe ) if using a 16 mm pipe.Figures of 50 mm-60 mm total. are often quoted as the "optimum" thickness to act as a heat-store.

I would never - under any circumstances - consider anything except pump-delivery as the quantities are just far too large and there is no cost-saving ( when I did it anyway)for self-mix vs pumped delivery.

 

[dilalio]

Thanks very much dilaio, why is the need for such thick screed?

Because the screed absorbs the heat from the pipes and radiates it out more evenly throughout the space much like the concrete blocks in a storage heater... Once warm it uses little energy to stay that way, initial heat up takes a while, so you keep it at a low level for comfortable warming.

 

[jeds]

Use a simple standard specification. Even out floor, if necessary, with self smoothing compound. Lay insulation - no adhesive required. 1000g poly layer over and clip UFH through poly to insulation. Fix 30-40mm insulation upstands to perimeter and finish with screed. The normal minimum is 65mm but some branded screeds go down to 55mm.

 

[Andehh]

Thanks for the advise guys, I am now leaning fully towards doing it properly and ripping everything out.

With getting the screed pumped in, the lorries obviously have a boom on them to get the pipe in the right direction, how much can the pipe be extended to get into doorways and down hall ways etc?

As for upstairs, again with being nervous about how much weight the 120+ year old house can take, I was looking at extruded polystyrene tiles like the below, then screwing them down to the floorboards (bigger washers & being careful) then over plying before carpets etc are installed.

http://www.theunderfloorheatingstore.com/insulation-boards/water/25mm-solid-floor-panels

Is there a better way of doing it on upper floors?

Thanks again

 

[mointainwalker]

Just to make sure I understand. Are you proposing to simply run the water pipes in the insulation panels without screed ? If yes I'm not sure how effective that would be as the heat output would simply follow the line of the pipe instead of diffusing through the total surface area of the screed and you might be very conscious of cold-spots.

An alternative to this would be to use electric UFH which can work with as little as 10 mm (?) of screed but I don't know how economical that system is or what the components cost.

As far as pump delivery is concerned, this is how it was for me in France, however I have no idea if the same systems are used in the UK. I used a flooring-company and they ordered the pump-lorry with basic mixture from the local concrete suppplier: the lorry pumped into a secondary mixer ( size of a very large air-compressor) which after mixing and further diluting, pumped the mixture through a pipe (30 mm/50 mm ?) into the house. In my case there was probably 40-50 m of pipe in use and I don't have any memory of there being any problem with the length, so probably more available if needed.

 

[Andehh]

Thanks for the reply. Useful to know that's how the screed would be delivered, that'd work refine for us.

I was figuring the plywood, underlay and carpet would help defuse the heat, and the insulation in the bose helps push the heat you and not into the void underneath they floorboards.

The other options us 50-60mm thick polystyrene sheets with the grooves in place for the pipes, then mount these between the joists. This way is obviously just a lot more labour intensive!

Electric UFH would be eye Wateringly expensive in an old property in the peaks, especially as the house is desperately exposed to the elements!