Mini basement/wine cellar idea

[Rich_t]

Hi all,
I'm replacing my kitchen in the next few months and I'm toying with the idea of creating a void below the kitchen floor and using it as a mini cellar/larder. I've seen ready made spiral staircase wine cellars, but that's way more sophisticated than I'm considering. It seems like an obvious storage place, but I can't find any examples or discussions of it online so I wonder if anyone could suggest any gotchas that make it unfeasible, or at least not worth the trouble.

This is what I have in mind:
A void, roughly waist deep once finished. Basically a cement lined box to install movable shelving into, where I can store homebrew and wine plus other stuff that's better off in a larder/cellar than a fridge or a cupboard. Access would be via a well insulated trap door to create a thermally stable space that doesn't have the daily and seasonal temperature (or humidity) variations that the rest of the house has.

My property is a 2 up 2 down terrace house in London built in the 50s and I own the freehold. The excavation would be over a meter away from either party wall. None of the utilities run under this part of the floor and it isn't too close to anything structural.
I assume the floor slab is about 4 to 5 inches thick, but it's too hard for me to drill through, so I wouldn't know what lies beneath until I hired a cutting tool. There is also some sort of black leveling layer on top of the slab, about 1-2cm thick, which is much softer.

Any advice on whether or not I'm barking up the wrong tree here would be greatly appreciated.

Regards,
Rich

 

[Doggit]

This is always a difficult one to advise on, without being on site. And I can guarantee that this should go through building control to make sure you don't undermine the foundations.

Although you're going to be about a metre away from the wall, you're going to be going down below the existing foundations, albeit not by much. You could do worse than digging a small shaft by the wall, and see how far the foundations go down first.

You say how far you are from the walls, but not how big you intend to construct the pit. Ideally, it'd be as narrow as possible, but long; that would allow you to have a set of steps at one end, but not being wide, you could maybe get a door to act as the trapdoor/floor. But I'm not sure how much you need to bother insulating the door, as the temperature in the pit own't be that low, but it'll be constant. I'm not sure what the black stuff on the floor is, but it may well be the damp course, so you need to make sure the concrete has a damproofer in it. Although it would be easier to dig the trench, put up the shuttering, and then fill behind it, it would be safer to do it in metre sections, with at least a 75mm wall of concrete, or even 100mm thick to play safe. Having got the walls done, you can then fill in the base at 50mm, and then do the steps. But having said that, if you you stick to a narrow trench design, then it could be done in one go. Dig the trench, construct the shuttering, fill the sides, and then do the base and the steps. Then thouroughly tamp down the sides of the trench so that the earth is packed tight back to the frame.

 

[Diver Fred]

The 'Black Leveling Layer' you describe I think is likely to be 'Pitch' (thick bitumen) - the damp proof layer for the floor. Not wishing to be a 'kill joy' but I'd leave well alone without professional guidance (and by professional help I mean a old and wise builder who has worked on properties with pitch dampproof layers).

Pitch needs heat to soften sufficient to lift but is imflammable, can and will 'creep' when cut or lifted. I guess you have a wooden floor which the joists are sitting on metal plates which the pitch is surrounding.

 

[Doggit]

I don't think it's be pitch, as that's also soft, but it's something to be considered, and to be wary of. But if it is, then you should be able to cut it, and then scrape it off. I realised that I'd forgot to mention that if you do this, you need to allow space for the "door frame" when you pour the concrete, so it wouldn't come up to the top. You'd also need to think about setting your trap door in severla sections so that you can actually lift it.

Not bad a dvice to get someone experienced to look it over.

 

[^woody^]

Probably ony useful for keeping fruit cake in.

 

[Rich_t]

Thanks for the replies.
The black material could be some sort of pitch. It is brittle and a little loose in places though and has no tarry smell to it. It wasn't singed when my bit got hot either. There are no floor timbers. Floor tiles (of a melamine like material) are fixed directly to it in the living room.
I imagined it about 1m wide and up to 2m long, then refitting an insulated floor over it and having 2 hatches about 0.5m wide along the centre with various racking under the floor each side of the hatches. I'd make wooden steps so that I could move them to either end. I'd fit pistons to the doors, like the ones that assist a hatchback to open, if I did build this. I don't want doors that did my back in or risked over balancing me every time I opened them.
My builder is a young Polish chap who's been very good so far. He's fitting our new stairs next week. I wondered if a project like this could be done as a DIY or semi-DIY project though as he's worked his way through quite a lot of our savings already and I want enough left for the kitchen.

I don't think I'd be keeping fruitcake in it (apart from myself perhaps, when my wife tells me "you built it, you can @#$$ sleep in it now").
We have a lot of dry ingredients that would keep better in a dark stable environment and I'm getting into homebrew now and finding I have to keep bottles of ice on hand and stand my brew bucket in a water bath in the current weather (and I'd like to "cellar" my creations too, to see how they develop).
This seemed like it could be a cost effective micro-cellar and welcome increase in kitchen storage space, that hopefully didn't require planning permission.

 

[Doggit]

As long as you're careful when you dig, and you don't come across any services, then it's a diyable project. What's the size of the room though as I'd be inclined to stretch it a bit further. The gas struts are a good idea, but will only work on either end, so you may end up with a small central section that needs to be lifted, but could then be clipped to either side to hold it in place. If you're upfront with him, he may find someone who'll do the digging cheap, the he shutters and pours the concrete, then maybe you fit the doors.

 

[Rich_t]

Downstairs is open plan with a structure that includes the fireplace in the middle, which supports the first floor and loft of the property. The only other walls are the perimeter ones.
The kitchen is currently about a quarter of this, but we'll extend it a little into the living room to take up a floor space of around 4m x 3m. (Approx. 4m from the back wall to this central structure.) There are no utilities under the area that would be excavated.

My wife and I built our own conservatory a few years ago, after I noticed the builder I hired trying to hammer the securing screws into the brick wall. That seemed a but unconventional considering the screws were to join the conservatory wall to the house. I realised I couldn't do a worse job than he was about to do. It was a real learning experience, especially fitting the roof ridge then lifting the roof glass into place. I'd never seen glass bend until then. It has been sound and leak free since and we just about managed to avoid divorcing over my foremanship "skills"
The property seems to be built on the ruins of old London. I'm sure I extracted more rubble than soil from the conservatory foundation excavations (but no bombs ).

 

[Doggit]

The danger you've got from being built on rubble, is that it may slide as you shift it, so be prepared to do a test hole in the middle of the room, and to fill it back in if necessary. Now it may not be as bad as that, as the foundations should be built on solid ground, but they may've thrown the rubble back in rather than get rid of it. Do you have a 105mm diamond core drill to do a test hole.

 

[Rich_t]

Ah, when I said rubble, what I found appeared to be the foundations of previous constructions. I dug up the remains of walls and fireplaces etc. constructed from irregular hand made bricks under the garden. It wasn't material the builders of the current property buried. I don't think I found anything that looked like left overs from these current properties in fact (but whatever is under the house is a different matter of course).
I took a chip of the black material and burned it on the hob. It does melt and bubble a bit, but there was no smoke or smell. It seems to include some kind of resin but not obviously derived from bitumen, unless it loses its flavour after 60 years.
I actually have a diamond cutter set that I forgot I have, so I probably will cut a core out before we start the kitchen.

So far it seems like no-one thinks it's an obvious nonstarter for regulation reasons or because it would cost too much to do it right. To me it felt like a hole in the ground that just needs to be properly constructed to meet building reg's for a safe space within an appropriately insulated home.

I also mentioned it to my wife tonight, very tentatively, and she loves the idea That's a first in over 12 years.

I'll pass it by my builder to see what he thinks about it. Thanks all

 

[Doggit]

I have no idea if a hole on the kitchen floor constitutes a basesment for building regs purposes, so it's up to you whether you put a quiet question to the local office or not, but as long as you're careful not to disturb anything, then I'd say it was feasible. Obviously, the further down you go, the colder it'll get, but I'd say stick to about 4ft, and work out where you will stack bottles etc, and can you get past them. If everything along one long wall was racked about a foot wide, could you sensibly walk along with a remaining gap of 600mm, which adding your foundations, means you'd be digging the hole about 1.4m wide.

 

[Rich_t]

I've emailed our planning office explaining the project and asked them if it requires planning permission and whether there are features I shouldn't include or dimensions below which it would be a permitted floor modification.
All the literature says you need permission to excavate a new room or new story for the property, but floor modifications seem fine. It all depends whether they feel this is a new room or just an alteration to an existing one. Perhaps the feature I'd need to avoid is the door in their opinion "If you plan to have a door then it's a new room sir, isn't it."

I think thermal fluctuation in the house would be the dominant influence on this space, compared to digging a bit deeper. As long as I properly insulate the space from the rest of the property a foot more or less depth probably won't change the temperature. If I'm generous with the wall concrete and sub-floor slab and make sure there's no air gaps between them and the soil then I should have a reasonable thermal mass at subsoil temperatures (and well away from soil that is exposed to weather). I'd also undermine the existing floor slab a little extra and back fit with an insulating material to thermally isolate the new concrete from the existing floor (as long as that can be done without compromising damp proofing efforts or floor strength). I also intend to raise the floor level downstairs a little to retro-fit insulation. That should reduce thermal flow into the ground even more.

 

[garyo]

There are various under-floor storage ideas curated on Pinterest... you'd then be talking more about a cupboard in an existing room that happens to be under the floor. Have you thought about a storage rack that rises up out of the floor on counterweights so that you don't have to worry about stairs? That might then significantly reduce the scale of the excavation (and even the depth) without reducing the overall storage capacity.

 

[Rich_t]

Yes, I've had a good scan through Pinterest. (That’s what inspired me in fact.) Quite a lot of those are spiral staircase boreholes with shelving round the outside but (I'm guessing) that's way above my budget and probably goes deep enough to constitute a proper basement extension to boot.
I feel my idea is no more than a cupboard under the floor and hope the planning office would agree.

I did think about a counter levered cupboard that pops up but there are a lot of compromises with that: If the lifting device fails that would be a pain. When it raises up, everything has to come up together and there's a big weight difference between an empty and a full cupboard. It's technically more complex than a hatch and could easily end up looking jerry-rigged or behaving dangerously or, worse, locking me out of my beer. It would be really cool if done right though, pulling a handle gently and watching a whole wine cellar glide effortlessly out of the floor.

A trench with racking either side would offer as much space as I'm prepared to excavate with complete flexibility on shelf layout (and future reconfiguration) and have more thermal mass with less fluctuation when accessing it. The trench itself could be utilised a bit too, so it wouldn’t be a dead loss. It would be ideal for sitting a brew bucket, demijohns or a beer barrel in, etc. In principle I could even grow mushroom packs down there etc. I am also wondering if I could include a couple of hanging bars under the hatch so that some regularly used things can retrieve themselves by sitting in a gondola, but that's all in the detail, contingent on building the space first.

I think the sump should be as simple as possible and then I can go to town on how I use it at my leisure. I don’t have a great track record of finishing ambitious projects swiftly and the novelty of a ½ finished hole in the middle of the kitchen may wear off quite quickly.

 

[Rich_t]

For anyone else who likes this idea, I've done a bit of lunchtime research and found the following.

Firstly advice from one of those Spiral stair cellar companies, most of which applies to my idea too:
"Planning permission is not normally required because the Spiral Cellar is not considered a habitable space, but may be requested by the Local Authority if a property has already undergone extensive extensions or additions or is a Listed Building."

"Building Regulations Approval is required when installing into a habitable space such as in the home or an attached garage. It is not required if the cellar is to be installed in most single detached garages or outbuildings. A Spiral Cellar is not a habitable space so the cellar does not need to comply with Part K of Building Regulations." (i.e. staircase regulations.)

"Party wall awards are applicable to a Spiral Cellar installation if the excavation is planned to be within 3 metres of a neighbouring owner’s building or structure."

However my proposal is much shallower work and the party wall act seems clear regarding permitted depth of excavation:
Section 6(1) applies where -

(a) a building owner proposes to excavate, or excavate for and erect a building or structure, within a distance of three metres measured horizontally from any part of a building or structure of an adjoining owner; and

(b) any part of the proposed excavation, building or structure will within those three metres extend to a lower level than the level of the bottom of the foundations of the building or structure of the adjoining owner.

The Isle of Dogs, where I live, is reclaimed marshland with London clay about 0.8m below the surface requiring deeper than typical foundations and also the current ground floor level is at least 10cm above the original ground level of the site so, in my case, there seems no risk of The Party Wall Act being applicable. I would only need to be mindful of building regulations therefore, which I think my builder can sign off on himself, as long as he does that part of the work.