Replacing Cellar Floor

[Algernon]

Hi All,
I joined to get some advice, really.
We have a Victorian terraced house in Kent. Standard little 2-up, 2-down with an extension at the back and a small cellar below the front room.
The cellar floor was (still is, in parts) chipboard on partially suspended timber over earth, sealed round the edges with expanding foam. The foam doesn't seem to have helped at all.
Anyhoo, I recently put my foot through this moist organic layer and have realised at least half of it is hazardously decayed. I have also been farming wood boring beetles under there so will have to get a chap or chapette in to treat the timbers above and around.
I want to put in a new, inorganic, decay-proof floor.
Having done some browsing, I see that trying to seal the damp out is a losing battle, so I am thinking of some chunky gravel on the earth, topped with limestone flags. I am pondering grouting it - I don't want to seal moisture in but equally I am keen for an appealing appearance -I hope to use the room as a workshop / man-cave.
Can anyone see any problems with my plan, or make any suggestions as to how it could be improved upon (e.g. should I use sand over the gravel, or will this be likely to wick moisture up from the earth below?)
I am currently running a dehumidifier down there which pulls about 5 litres in 3 days but I have not measured the humidity itself.
Looking forward to hearing your thoughts (unless they be horribly expensive and preceded by lots of digital tooth-sucking, of course ;-)
Cheers,
Algy

 

[JanJonWestWales]

Dont try to seal it in - waterw illalwys find a way - it needs to breath and then be removed - open door, window fan, de-humidifier(expensive) - adding warmth accelerates the process.

Lookup limecrete floor.
Essentialy a layer of blown glass - which acts a breathable water barrier (if thick enough the water cannot wick up through it)
layer of breathable membrane
Layer of Lime - usually NHL5 or NHL5z (with pozzolan) for a hard but breathable floor

I've layed this in a damp hallway (8'x8') and it works a treat

Alternatively, and still with lime - I have a cellar that had a cobbled floor direct onto shale bedrock. It had a small stream runing though it, run-off from the shale house foundations, and water running out of the walls. Subsequently most of the joists of the room abaove were shot, and a supporting post for the main beam was dangerously rotten.
Dug out the cobbles, diverted the stream through a channel with perforated pipe (in a bed of gravel).
Covered with a thick (6-12") of NHL5, and layed the cobbles back in
Limed the walls (putty) and fitted a solar powered fan into a small cellar window
worked a treat, practically dry, in all but the wettest days.

http://blaencwmbychan.blogspot.co.uk/2015/05/back-to-basement.html

 

[Flyfisher]

'Man cave' is probably an apt description in the sense of caves being generally damp.

We have a small cellar with a dirt floor and soft brick/lime mortared walls. At some point in the past it has been limewashed, though it's no longer in great condition. In short, it's all eminently breathable and the dirt floor (sandy soil) is fairly dry to the touch, plus there is ventilation on one side, so hard to see how it can be significantly improved really.

However, in the summer it is quite prone to condensation and I've seen water droplets on the joists of the floor above, which is clearly not ideal for their long term survival - indeed there has already been some historical repair work where the ends of joists have suffered by being embedded in the cellar walls, but it's all basically stable. To keep the condensation under control, I've been using a dehumidifier during the warmer months and it has completely stopped any water droplets forming on the joists, which is not entirely surprising as it seems to extract a couple of litres per day.

Fortunately, I'm not trying to make it a habitable room, mainly because I don't really think it's possible - it's a permeable structure buried in the ground and damp will be ever present, well until my dehumidifier has thoroughly dried out all the land for a couple of miles around! :wink:

Underground structures can be easily built to be completely damp-proof, but permeable ones are rather more difficult to change. I've heard of building an impermeable 'shell' inside a cellar and having some sort of siphon/pumping arrangement to collect and remove the water that will inevitably build up outside it, but clearly this moves us into the realms of some serious engineering.

I suppose it should be possible, with enough heating and extraction, to remove moisture as fast as it percolates into the cellar, but it all sounds too high-maintenance for me. I've no doubt that the cellar conditions can be substantially improved, but I have my doubts about habitability. A garden shed is generally a much drier place than a cellar but have you ever left a box of books in a shed for a year - mouldy pages galore

I guess I'm not coming over as a big fan of cellars as habitable spaces.

 

[Roger H]

Hi. As you don't have a historic floor to conserve, I'd be inclined to investigate a drained cavity system with a sump e.g. a Newton membrane.

 

[Tony.]

I don't see any issue with dehumidifiers, I have one set to a specific level, comes on and off as required.

Far cheaper than having to lift floors and replace.

A bit of heat/ some vents will work wonders, check exterior ground levels and with your post indicating a close water source, make sure this isn't going near the house.

I have an automatic fan I my kitchen with a humidistat, coming on when we cook and switching it's self off.
I think investing in fans, heating, humidifiers are a good long term investment.

All the best

 

[Algernon]

Thanks for all the replies so far - I'm glad none of them said "Stop! You're creating a monster!"
I am not aiming to get it dry. I have had a bench, fridge freezer and various bits of stored stuff down there and the only things that suffer are ungreased tools if left long enough, and cardboard if in contact with the chipboard floor.

Tony - I like your thinking with the fans and humidistats. I wonder if I could get something like my STC1000 brewing temp controller but for humidity. Then I could control a range of mains powered machines (extractor, dehumidifier etc) automatically.

Jon/Jan - I have looked into NHL5 - it looks affordable and if the gravel alone doesn't give me a solid enough base I will lift the flags and put a layer of that over/among the gravel.

I have looked at tanking etc and for what you'd get (a 10x12 ft room with damp creeping up the party wallsinto the ground floor proper) it is not something I would consider. Not worth the "investment".

Thanks again

 

[a twig]

Tony - I like your thinking with the fans and humidistats. I wonder if I could get something like my STC1000 brewing temp controller but for humidity. Then I could control a range of mains powered machines (extractor, dehumidifier etc) automatically.

Depending how "smart" and spendy you want to get - the Samsung SmartThings systems is rather fun. A small wireless hub in your home can take data from all manner of sensors and log it. It can also trigger actions via "smart" plugs. It can also send warnings to your phone if things are getting beyond set parameters.
http://www.samsung.com/uk/smartthings/ Details start halfway down the page, it can be found a lot cheaper elsewhere online.

For example you can set up the wireless humidity sensor, and put in a rule that once the hub sees a reading of 70%, it activates the smart plug that the dehumidifier is plugged into, thus turning it on. All the data is logged, so you can see the humidity of the room over time, and you can correlate that with the times that the smart plug (i.e. the dehumidifier) is switched on, and judge its effectiveness accordingly. There are a range of other sensors (water sensors for flooding, soil moisture levels for plant watering) and it also plays nicely with other non Samsung sensors, products and accessories.

You could also use it to aid with your brewing

I'm slowly putting together such a set up at home now, so I can track how the various changes to the house (lime replastering, insulation etc) are affecting dampness, warmth etc. Can you tell I'm an engineer!?