Good day all ,

I’m working my way through a renovation of a listed barn/oast, been a building on the site since around 1750 though how much of what’s here today is open to interpretation, it’s been much altered over the years.

Works so far have incorporated wood fibre bonded to external walls and baumit lime plasters, suspended ground floors have wood fibre and added airflow.
Now i’ve arrived at the ground floor in what was part of the barn. After removal of the 1980’s screed a couple of test pits show 3” of old concrete (probably around 1900) , 4” of crushed chalk , then 24” of made up ground mix of crushed chalk , clinker , soil. The bottom of this seems to be a compressed floor , possibly the original barn floor. Excavation for a foundation, uncovered an existing spread brick footing with air bricks suggesting that at some time the area had a suspended ventilated floor. This wall was not tied into the barn walls at either side so seems to be a later adaption and had air bricks stamped “doulton lambeth” and date 1858-1910. The building was repurposed in 1907 so this may tie in.
The area was last altered in 1980 (prior to this the area had been a handymans workshop and feed store for stables since the early 60’s), a liquid dpm between the slab and screed. Rear external wall has an exterior ground level 400mm higher than internal floor , this was similarly painted in liquid dpm ( wall is a mix of flint, brick and rendered partially on interior) then battened 25mm of glassfibre , polythene ( badly fitted) then plasterboard.

Stripping all this back reveals absolutely no signs of damp or rot. My preference is for a timber finished floor covering. ( previously the floor was finished with varnished cork tiles in the living area and a melamine type tile in the kitchen.)

The conservation officer is in the retain as much of existing as possible camp but is open to reasonable well argued options and has been very amenable to date. Costs are becoming very much an issue and saving on labour is becoming the easiest way to restrain the budget. A full blown excavation , foamglass, limecrete floor is whilst not impossible going to severly constrain the rest of the project. The simplest and most easily reversed option is 50mm max pir and a 22mm for the floor ( this is not much more than the screed i removed, any greater thickness of insulation is impractical due to two 9” deep beams running the length of the room) , external walls treated with bonded woodfibre as before.

Any suggested floor makeups? Is the simplest solution asking for problem in the future? My other post looking for a discussion revolving around the benefits of “dry” substrates having insulation benefits , was in relation to the infill in what was seemingly at some point a suspended floor.

Heating is gas boiler and oversized radiators , for a bit of future proofing and move to ashp.
There will be mvhr , more for continuous ventilation and negating the need for fan outlets in bathrooms ensuites etc than heat recovery as achieving really good levels of air tightness is unlikely , with the retention of existing windows and doors along with the timber frame remaining on show where possible and its likely movement as the place finally dries out properly.

Any thoughts / insights appreciated.