Dealing with different floor types

[mattwaddy]

We are just waiting on a completion date for our new house. It needs a fair amount of renovation starting with the electrics and plumbing, but as part of the work we would really like to install wet UFH. The property has mainly suspended timber floors downstairs with only the kitchen as a solid concrete slab. The property was built in 1969 we believe and so I doubt there would be much if any insulation in the slab. 

 

I'll be insulating the suspended floors with celotex and was thinking of using a structural system such as the omnie torfloor to avoid build up, then I'm left with the issue of the kitchen to deal with which would need an alternative. We've been quoted £2.5k to excavate and redo with an underfloor system with screed. I'm just wondering if there are any alternatives keeping in mind we may extend that kitchen down the line and so could maybe include the excavation at that point. I'm concerned that if we went for an overlay there would be a fair jump in floor height between the other areas and the kitchen. Also there would likely be some issue with door heights.

 

I'd like to see if there is a common approach to mixed floor types and how people have dealt with it. Also would be good to know what system you used. 

 

This is my first post, so sorry for the noob type questions. I just really need to nail this so we can plan the work ready for getting the keys, as we have two months to do the key work before moving in.

[markc]

Hi, if you do a bit of searching on here you will find loads of info, pros and cons of the different ways to approach this. Lot depends on the existing structure, build, insulation levels etc.

[mattwaddy]

On 16/09/2022 at 20:52, markc said:

Hi, if you do a bit of searching on here you will find loads of info, pros and cons of the different ways to approach this. Lot depends on the existing structure, build, insulation levels etc.

Thanks. I've gone back through 31 pages of the UFH section but can't see any specific threads where this same thing was covered, but titles of threads could be misleading. 

 

Sounds like the only real sensible option would be to dig up the slab in the kitchen so it can be insulated correctly and then use a structural flooring solution on aluminium plates for the suspended floor to avoid build up. Not sure I can see any other option.

[JohnMo]

UFH and poor insulation are a match made NOT made in heaven (expect big heating bills).  An alternative could be plinth heaters, design them to operate at the same temperature as the UFH would have, or radiators.

 

For the suspended floor, you may find installing PIR a real pain.  The gaps between joists may not be consistent and vary along the length, so getting a gap free install is not easy.  You may be better using something like Rockwool Flexi or similar.

[Temp]

+1  If fitting UFH must insulate properly. We have 80mm PIR and would probably fit double if building again. 

 

You also want to think about what's going on top of the UFH...

 

UFH also works best with tile or stone on top rather than underlay and carpet. If you want carpet it should have a low TOG value. Special underlay and carpet exist. Don't be miss-sold by reps that claim "all our carpet is suitable for UFH", they mean UFH won't damage the carpet, not the carpet will let the heat through well. Hessian backed carpet is better than foam backed but sometimes the T&C on the order form allows them to supply either version.

 

Engineered Wood works but a suspended wood floor must normally be >18mm thick (think it's a building regs thing). With care you can use 21mm Engineered wood on joists. Some people buy 14mm Engineered wood and then discover they need to put 18mm chipboard under it, giving 18+14=32mm. The UFH might still work but that 50% more wood the heat has to get through.