Lowering the concrete floor in a small room

[chuckf]

My 1950's, ex-council semi has a small (6'x3') cupboard that's potentially an ideal site for a second loo and washbasin. However, it isn't feasible to raise the low ceiling so ideally I'd like to lower the concrete floor by about 8". The new height is OK with the plumber.

Is this a reasonable undertaking? What materials might I lay down and in what thicknesses? And are the walls likely to go down as far as I'll need to dig?

 

[noseall]

i'm fairly sure, well structurally at least, that lowering the floor will be ok.

but there will be issues of damp prevention that will need addressing. there are tanking solutions that can deal with this scenario.

more alarming is the 8" step down into the loo though. at which point do you intend placing the step or steps? at the door threshold?

building control will need to look at the electrics, drainage and ventilation, so i would be interested to hear what they have to say.

 

[chuckf]

Many thanks for the reply.

Yes, I'd originally intended the step to be at the door threshold. The head height where you enter is about 6'2", which is reasonable. Then in the half of the room furthest away from door the height drops by about 6", which means a male of average height with shoes on (I'm thinking of myself as usual) would get a crick in their neck standing in front of the toilet. I can't really drop the height e.g. halfway into the room instead because you need the head height during the step down to avoid banging your head. I don't know if there's a compromise given the small size of the room?

I'd originally intended 8" as the maximum drop simply by measuring a step on my staircase. 5" would still be worthwhile for me at least, maybe 4" if it makes the job simpler somehow but anything below that and it's probably not worth it.

"Tanking solution" sounds interesting (read "pricey?") As regards ventilation, there's a window that I'd intended fitting an extractor fan in. Do you see potential issues with the electrics beyond the need for a pull switch, etc. as per a normal bathroom? As I say the plumber's OK with the new height as regards drainage.