Floor buildup, any ideas?

[Tom's Barn]

Hi All

 

We are installing cast iron radiators in our new house so that they are a feature as well as a heating system. From the insulated slab to the finished floor level (FFL) we have 45mm but could stretch to 48mm if needed. My wife wood like wooden floors (we will go engineered). So far I have come up with a plan for the floor build up but I just wanted to share this to see what the broader BH team felt was the right way to go.

 

So from top to bottom:

 

A. 20 or 21mm engineered oak flooring

B. 3mm Elastilon - very good and used in current house - https://www.jfjwoodflooring.co.uk/elastilon-underlay. This provides the structure for the floating and ensures gaps do no open up

C. 20mm XPS (300kpa) - this is laid across the entire floor area and because we are installing a wooden floating floor it does not need to be glued to the slab.

 

Some general thoughts and points about why I have chosen this approach:

 

1. I am always concerned with leaks and they happen in every house so having an XPS underlay to the wooden flooring will ensure I don't have a chipboard flooring layer (one other approach) that is slowly rotting below are feet if we did have a leak

2, The above approach can be fitted quickly, cheaply and it is much lighter than say using a self levelling compound to bring the floor height up.

3. In some PHs, plus on a recent visit to a PH that had a small radiator system, it suffered with something I have read before which is 'warm head, cold feet'. The visit we undertook was to a beautiful PH in the North Cotswolds, arranged through the Green Builing Store, but the first thing my wife said when she came out as just how cold her feet were - we had to take off our shoes becuase the light coloured wood flooring.

4. We have triple glazed windows, a well insulated roof structure plus we are not over glazed

5. In order to provide some thermal consistency (nearly said thermal mass but I know how you guys feel about that term) we will have wood floors throughout, we built the walls from the ISOTEX 380mm blocks, we have a 25mm service cavity on the inside which will be filled with Rockwool RW5 and then on top, a mixture of wood panelling and plasterboard. I know that we need to concern ourselves with the first 100mm in terms of thermal buffering so I almost have that amount before the concrete core of the wall system.

6. The building is not a PH but simply a well insulated building with expected low levels of energy needs

 

EDIT - I forgot to mention that I could put 25mm battens across the floor area and insulate inbetween; wood fixed directly to battens. This would negate the need for B and overall would be 2mm higher. A lot more work on installation but a much more solid final floor covering.

 

Any thoughts on a better way to fill the space currently described as B and C above?

Many thanks

Edited January 15, 2021 by Tom's Barn

[TonyT]

Can’t comment on the above apart from making sure you have a good noggin in the wall to fix the radiator to.

my cast iron rads have 10mm rods going into brackets fixed to the walls.

we used a few 4x2’s to get a decent fixing