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Garden pinball room - base question

Julian

Julian

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Bromley
For those of us that have built a games room in the garden and for those builders amongst us or just those 'in-the-know', I have a question regarding concrete bases.

I am planning to have built a 6.5m x 8.5m games room, now it will either be wood log cabin, or brick, apparently my ground is clay based, and I have 3 large trees within 4m.

I am hearing different things from the 3 quotes I am getting;

One says 2m deep concrete for a brick building.

Another says 4 or 5 strips of large stones/bricks cemented in a rows 1m deep with wooden bearers across is fine for a wooden structure, apparently the flooring will be as strong as that of a house! I guess this is like a suspended floor.

Thirdly, another log cabin company says 150mm deep concrete is all that is needed as this thickness they use in twin car garages, and large structures like welcome centres at Bird World.


I am at a loss to know who is right and which option is best without doing over-kill, any knowledge out there on this subject?


Cheers in advance.
 
2 metres of concrete, are they on crack? I would have thought 150-300mm on 150mm of compacted sub base.

Or you could forgo the base and use concrete piles or screw piles..

But i'm no expert.
 
2m deep concrete for a brick building does seem to be rather excessive but the builder is probably erring on the safe side due to the fact that it is clay with trees close by. Neighbour is just having a brick built kitchen extension, clay subsoil, and his 'footings' are 0.9m which he thought was excessive!

4 or 5 strips would work but again you would have to put concrete in the base of each one and then build up, labour intensive plus cost of wood bearers,

150mm is the usual that most log cabin companies quote and that would be on top of a base of maybe 100mm of road stone whackered down.

I had a base put down last year, 100mm of road stone and then 150mm concrete plus metal grid sheets in the concrete to strengthen it.

Bottom line is going to be what is your budget as 6.5 x 8.5 is one big building?

Brick or block built is probably going to be the most expensive option and depending on final spec could be £15/20k

What you may also have to consider is building/planning regs/neighbours boundary, max size you are supposedly allowed, depending on distance from boundary is up to 15sq m or up to 30 sq m, yours at 55.25 clearly exceeds that.
 
My base was put down last month. For a log cabin, all quotes were for ~150mm, re-enforced concrete.
My space was only 4.1m x 5.6m x0.15m (3.44m3) and that was a lot of soil removal and concrete. I had a chalk where mine was but with some compacted stone.
2m depth sounds really excessive and results in 110.5m3 of concrete and at the prices I was being quoted would cost £11k for the base alone.
0.15m to 2m sounds way to much variation, double check it.
 
The "One says 2m deep concrete for a brick building." would presumably be for the 'footings' and not a complete 6.5 x 8.5 x 2m base?

So would still be quite a lot of concrete but not 110.5m3.

Would still be a lot of digging and would need mini digger, skips (unless you have somewhere in the garden to dump a load of clay?)
 
If it's of any use:

We're getting a local guy to lay our concrete base this Monday. I'll try and do a before and after photo.

It's a 6.5m x 5m square with a step-in on one corner so it fits at an angle next to the house (ensures room for roof overhang and guttering). Will be a dual purpose Architecture office (weekdays) and pinball room (evenings and weekends). Not sure of construction yet, but most likely well-insulated timber with some blockwork. The Mrs. is designing it but busy with real paid work at the moment. Only room for 5 games to begin with, 10 if she decides to relocate to a real office (or kicks me out to another building!).

3sq metres of concrete going in, plus some steel reinforcement over the previous garage base (large car sized patch, but well cracked). So that's only about 10-15cm deep, maybe a bit more towards the edges.

We're paying £950 all in. Skip to remove earth, labour, concrete, etc.

**** knows what soil type we have. 'Brown' coloured is all i can tell you. No trees close by.
 
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Monkeyboypaul, thanks.

Are you getting a sub-base or hardcore compressed before the concrete is poured in? What about steel re-enforcing mesh and depth of concrete.

Please keep me posted.


Cheers
 
Is the '2m' a typo and it should be '.2m', with the caution being its 200mm deep rather than what seems to be the more common 150mm?
 
Hi
I'm a builder myself built a few games rooms through the years if building a brick or blockwork games room dig a test hole at your house down to the underside of your existing foundation that will give you an indication of what you might need to dig to do the foundation for your games room,personally myself when it is clay I dig down about 1.1then put in 450mm of lean mix concrete then put in 200mm of 35n concrete with reinforcing mesh,this will leave you with 450mm frost cover so you can then lay your two courses of blockwork which will give you your floor height,make up of floor as you have got 450mm to play with could be 150mm type1 stone,vapour barrier or dpc,100mm insulation,150mm concrete,for a log cabin I would do the same and sit it on it or keep a course of blockwork off it an fix a wooden shutter around the perimeter and pour concrete to desired height then sit log cabin on it.

Hope this helps
If I can help anymore feel free to ask

Cheers Brian
 
Julian said:
Monkeyboypaul, thanks.

Are you getting a sub-base or hardcore compressed before the concrete is poured in? What about steel re-enforcing mesh and depth of concrete.

Please keep me posted.


Cheers
Click to expand...

I'm not sure what's going underneath the concrete - possible the old base after being broken up. Yes to steel mesh.
Not sure of concrete depth, but i think i worked it out to about 10-15cm in my message above, which equates to @Paul 's comments of 4-6".
 
With regards to steel reinforcing - it depends on your mix. Dont forget to have the polypropolene fibres added (only adds about 20-30 to the cost, however prevents the thing from cracking, which is the key...
 
Julian said:
Please keep me posted. Cheers
Click to expand...

Current progress:

IMG_1420.JPG

There's a deeper channel around the edges, averages about 350mm deep and 200mm wide. Then there's the muddy plateau surrounding the old garage base, averaging about 300mm deep.
The old and knackered garage base is 150mm higher. Then the final concrete level will be 100mm higher again. Steel mesh going all over it and (as you can see) hardcore going in too.

Now looking like 4m3 of concrete instead of 3.

The build will be very well insulated timber looking like a less-fancy version of this (but still with the vertical timber cladding):
office.jpg
Don't forget it's also an Architect's office, so it has to look semi-smart!

Probably have a ring of blocks around the base to drop the screed floor and insulation into, then we build the timber walls on top.

Some rough plans/drawings also attached, including scribbles all over them.

How's your build coming along?
 

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Looks like this is going to be an interesting build Paul so if you haven't done already might be worth starting your own thread specifically for it and then it will be easier to follow :) :thumbs:
 
No movement as yet, although my current logcabin quote includes strip foundations that the wooden bearers will sit on, I was worried about stability but have been assured that it would be like a houses raised floor (where my pins are currently) so I guess that will be ok.
 
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