Soil under suspended floor

KetoOptimized

I've taken a peek under my suspended floor as it was getting a bit whiffy, and found that there is just soil as the ground. My home is a 1930s build so its probably to be expected. I would like to redo the subfloor at some point because the floorboards have gaps and I imagine I should sort out the ground first, but I'm not really an expert on this and my research is giving me mixed signals on what should be done about it. Do I... leave it as is? I've read moisture can come up from it which seems likely in my case. Do I... cement over it? Put rocks? I'm really not sure! Can anyone point me in the direction to make this right before I add floor insulation/new floorboards and maybe some pros and cons of each approach. 

sew_what

Ours has been like that for 80 years!  So long as there is a good flow of air through your airbricks & no running water, I can't see there being an issue.
It's very useful space for running wires & pipes!
Did you find out what the smell was?  We've found the odd expired rodent under ours!

Mickey666

Main thing is to ensure there is good ventilation under the floor.  Check for airbricks and that they are not obstructed.  Ideally there should be airbricks on two (or more) walls to maximise airflow.  This ventilation will dissipate any moisture that rises from the soil.  Laying impervious concrete is unnecessary and might even make things worse by forcing any dampness up the walls. Limecrete would be a breathable alternative but would still require good ventilation of the underfloor space so would really be just a waste of time and money.

My house has some rooms with suspended floors over bare earth and good ventilation means there are no problems.  Not sure how old the floors are but probably well over 100 years.  

twopenny

My house was 90yrs old and this was the norm. There was always a small a draft coming through the floor boards. In the colder rooms I used papier mache to fill the gaps and round the skirting with no ill effect. There is now a sealant they make for old floor boards that does the same thing.

You need to be careful of altering the status quo as your insurance might have something to say about it should things go wrong and you get damp or rot.

scottishblondie

You don't need to do anything about it.  Our house is 1920s with a similar space under the floor.  Under some of it there is cement (an old basement area that was filled in for some reason in the 1990s) and the rest is basically soil and rubble, which can definitely be a bit damp and dirty.  As long as it's well ventilated I wouldn't worry.  It does tend to smell a bit musty, but we only ever smell it when we've opened one of the access hatches. 

Most of our floors have been insulated at some point in the past with fibreglass bats in between the joists held up with netting.  It seems to do the job pretty well.  I would look at installing insulation from below before considering lifting all your floorboards and replacing them, as that is quite a job and will require a lot of upheaval.  It's really only necessary if the boards are in really bad condition.  Most likely the boards that are down were never intended to be the final floor covering, so if you have them exposed currently adding a new hard floor or carpeting will also help to cut out any air coming up from below.

Mistral001

The thin layer of concrete that is put over the soil under a timber floor is there mainly to stop burrowing rodents.  It is also sometimes used as foundations for intermediate supporting walls for the floor joists.  As has been said, if the floor void has through ventilation there should be no moisture coming from the soil.   I would check for rodent problems but they are unlikely to tunnel under the foundations so unless you see signs of them burrowing or droppings etc. I would not worry about the fact that there is not a protective concrete layer.

stueyhants

I had similar and filled with insulation and a new concrete floor with wet underfloor heating. You need to be careful and make sure your wall DPC is robust as the water that used to vent under the floor will just sit there and expose any weakness in the wall and cause rising damp.