The floors in my 1930's bungalow are concrete covered with bitumen into which floorboards were laid (presumably when the bitumen was hot) and then nailed down with flooring brads - apparently this was common in this area at the time and the architect who handled the kitchen extension gave me a name for the technique, which I've now forgotten :-(
Anyway, I'm now looking to sort out the bathroom and want to re-lay the floor.
Googling around has given me the suggestion of pulling up the old (warped) floorboards, scraping off the loose bitumen and sealing with Ardex Epoxy Primer.
The question then, is what to replace the old floorboards with.
I'd like some sort of insulating filler to then lay floor tiles on, but what is there?
Closed cell polystryrene foam with both faces finished with glass mat impregnated with cement.
It takes tiles wonderfully (use a Class S2 flexible adhesive and flexible grout - essential).
But for this application, you really want to bond the marmox down to the subfloor, which may be difficult with the bitumen. Even if scraped off, bitumen is a bastard for shearing the bond with almost anything else poured on top that isn't itself bitumen.
One solution that was employed by my plaster when he was doing a flloring job in Germany in a previous life (old underground military complex, bitumen on floor, needed levelling compound and new floor surface) was, under the guidance of an expert in such matters:
Drill loads of short holes (say 1cm deep, every 5cm) in a grid.
Pour on self levelling compound.
The compound runs into the holes which gives it something to lock onto. I'm not sure what the thickness of the compound was though. a 1cm thick pour would almost certainly have enough strenght with such a hole spacing, but
5mm may not.
As it is only a bathroom My inclination would be to hire a small floor grinder (angle grinder sort of size, but has a guiding frame) and take the top mm with the bitumen off completely.
Messy, but if you tape yourself in with plastic sheet and wear a mask and googles it should be possible not to destroy the house(!).
I used a lawnmover sized tungsten flail grinder on mine as I had a 21m2 floor and I wanted to grind 1cm off in places - that *was* messy.
I suppose it might also be possible to bond the marmox down with bitumen.
The last resort method would be to screw the marmox down - you'll need stainless or brass screws in a grid - check the marmox data sheet for recommended spacings, they do have this as a method.
Someone mentioned Marmox, I think Depron might be another alternative.
Marmox is piggin expensive - so look for PCS and similar...
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look at underfloor heating, insulation and they do 6-10-20-30-40-50-60mm. Only Marmox AFAIK do 12.5mm thickness which is more useful re butting up to plasterboard and such like (usefully stiffer than 10mm re batten positioning).
Floor insulation makes quite a difference, had one quarry tile area over uninsulated concrete and with rubber tredaire & carpet it was miserably cold on the calves. Replaced with a felt backed carpet and thickest Cloud 9 (might have been Tredaire equivalent). No cold, room warmer, soon flattened down to feel little different to rubber tredaire but kept the insulation (TOG rating).
I must admit I was thinking of using the (possibly bitumen) stuff to repair felt shed roofs - I got tin of it to fix a shed roof which I didn't use in the end as I had to completely re-felt it.
Dumping a load of that on top of the old bitumen (it is a small bathroom BTW) and then laying/fastening something on top seemed like a possibility.
The problem I have with screwing/nailing through the bitumen is that it makes a hole in the damp course - mind you, that's what the original flooring brads did anyway ;-)
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