New Shed

Am in the planning stage of a new 14'x14' shed, and have a few questions.
What depth of hardcore to use under the 4" slab? How can I get rid of the tree stump in the way? Bear in mind I'm notoriously cheap. What timber size would be good for the roof frame? Thinking of doing the roof with OSB followed by corrugated steel.
NT
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On 28/08/14 12:22, snipped-for-privacy@care2.com wrote:

Oh. wet fingers depth. Hoew thick is the slab? Ok 4".. thats decent enough Do you care if it cracks a bit? are you on clay? are there any trees nearby...

Get in a mini digger anyway. Dig a trench round the tree to expose any lateral roots, cut em with an axe, and the hoick the whole thing out cutting any bits that seem to prevent you.
Bear in mind I'm notoriously cheap.
Matey a mini digger is about 130 quid for a day. If you use that to mash up the site and level it. you will at least have a more or less predictable scenario under the slab. Then use rebar when laying te concrete slab. With your hardcore and sand under to get decent drainage and have the possibility of some soil movement that can be absorbed by a loose fill later.
In genearl remove any large lumps, and enoiufg depth for waht you want, stick dp0wn 4-6" of hardcore and sand, then revbaber propped up an inch or so, then cast te slab,
You probably can actually build any walls right on to that without a DPc, or foundations, or if its all timber, just make sosme small brick spacers to space the wood work off te damp concrete

2 x 4 should be well OK.

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On 28/08/14 12:22, snipped-for-privacy@care2.com wrote:

On compacted undisturbed soil, you can get away with little more than sand with about 1 part in 8-10 of cement overlaid with slabs on smaller sheds.
A 4" slab would work direct on soil (though it might move a bit over the years), but if you want industrial, 6" Type 1 MOT plate whacked down to about 4" under the concrete would be very very stable.
For less physical effort, have you considered just pouring 2 strip foundations about 6" wide and maybe 1' deep ontop of a trench of well rammed hardcore then running 4x2" decking joists between them at about 400mm spacing?
You'll raise the structure but OTOH you'll have good ventilation under the floor.
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On 28/08/2014 12:22, snipped-for-privacy@care2.com wrote:

Spade, axe and scaffold pole and lots of time depending on how big the stump was. The resulting hole will cause you problems with settlment.
My former pear tree location down to grass is still susbsinding slightly years after removal of the main >1" roots as the smaller stuff gradually rots away and shrinks. Annual top dressing fixes it on a lawn.
Regards, Martin Brown
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On Thursday, August 28, 2014 12:22:02 PM UTC+1, snipped-for-privacy@care2.com wrote:

That sounds like a bit of overkill on the roof. Would corrugated not do on its own. Its likely going to be the strongest component anyway
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Unless there is some reason for having a concrete floor, such mounting heav y machinery, I would go for the raised wooden floor and get the benefit of ventilation. In that case all you need to do is support the floor on piers be it brick, stacked flags, concrete filled pipes or you can use fancy conc rete and metal adjustable piers, see example here,
http://dunsterhouse.co.uk/faq/388/rapidpad-foundations-for-modern-offices
Raising the floor enables you to eliminate rising damp problems and also to insulate underneath the floor.
Richard
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On 28/08/14 16:49, Tricky Dicky wrote:

The BIGGEST problems with a raised floor is getting wheeled garden machinery in and out.
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rare story of which you happen to have first-hand knowledge. – Erwin Knoll
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On 28/08/14 20:02, The Natural Philosopher wrote:

Ramp?
Of course - it depends on how heavy :)
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On Thursday, August 28, 2014 8:02:20 PM UTC+1, The Natural Philosopher wrote:

Too true. I made that mistake with the first shed I built and using a ramp is only a p.i.t.a. Though I loathe working with concrete I built another shed alongside it with a concrete floor. Their both full now.
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Depends on what is there now. Nothing is fine if its well compacted dirt.

There is only one viable approach, dig it out.
And you have a problem with the hole that remains particularly if the hole is quite large.

I'd personally go for a flat metal decking roof instead. You need a lot less frame for that so the total cost is going to be lower.
OSB followed by corrugated steel isnt going to be cheap.
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On 28/08/2014 19:59, Rod Speed wrote:

OSB lets you use that very thin plastic coated steel sheet which is pretty cheap. This sort of thing.
http://www.ebay.co.uk/itm/1-LINEAR-FT-DARK-GREEN-JUNIPER-GREEN-PLASTIC-BOX-PROFILE-SHEETS-SIDE-CLADDING-/121399541888?pt=UK_BOI_Ceilings_Walls_Roofing_ET&hash=item1c43fa0080
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newshound wrote:

    Those sheets look like wall sections and I reckon you're going to need a lot of screws and washers to hold it down. Every screw hole is a potential leak. The sections also need to be held down and sealed at both ends or the water will blow in under the corrugations. My Screwfix nightmare shed used this stuff and it took ages to build, millions of screws and umpteen tubes of sealant to make it waterproof. TMH had an identical bad experience IIRC.
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wrote

Sure, but what matters is the total price.
I doubt that would compete with metal decking and a flat roof with the total cost of the roof including the roof structure.
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It is a while since I bought this stuff but my recollection is more like £1.00/m for 0.5mm painted finish. More for plastic coated obviously. Check the price with a local outlet.
One problem with any metal roofing is underside condensation. Worst case is cattle housing in frosty conditions where it *rains* inside when the Sun comes out:-) You may want to consider some waterproof layer protecting your OSB. Roof pitch is an issue with 12.5deg. the minimum for agricultural buildings.
Pitched roof is nice as you can store lots of junk on the tie beams. Downside is two lots of gutter/rain drip to deal with.
There are issues with how close you can construct a timber building to a boundary as discussed previously.
--
Tim Lamb

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On 29/08/2014 08:31, Tim Lamb wrote:

True, but with panelling on OSB you are limiting access of moist air to the underside of the metal. Can't see that a couple of coats of bitumen paint would do any harm though.

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Fixing screws have neoprene sealant washers and are fitted in the VALLEYS:-)
Expanded foam strips are available to seal the ridge.
Stitcher screws every 0.5m up the laps. You can get rolls of butyl strip (sticky one side) to seal the laps.
One point... metal roofing is noisy. Every time a cloud covers the Sun the stuff shrinks.
You might find something useful on the Steadmans site http://www.steadmans.co.uk/
--
Tim Lamb

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writes

Don't get any effect like that with metal decking.

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On 28/08/2014 12:22, snipped-for-privacy@care2.com wrote:

Don't forget to check out what you need in respect of planning and/or building regulations approval first.
--
Peter Crosland

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I should explain more. Interior climate is important, it must remain dry an d avoid extreme temp swings. Hence the choice of an underboarded roof and a slab that will moderate temp swings.
The shed will contain floor loads of 5-10 tonnes. The plan was to do a 2 st age build. First a quick cheap timber structure will go up, then just insid e that will more slowly go up a breeze block structure. When the wood rots the breeze wall will be rendered. However it seems it would be cheaper to j ust do block - which is better largely comes down to timing, there are issu es I wont bore you with about that.
So a suspended timber floor is impractical, it'll be concrete slab - unless scalpings would be workable. We don't have anything set up to heat or comp ress them though.
The Natural Philosopher wrote:

There's a biggish tree right next to the proposed shed. The soil's clay & w ell settled. I guess masonry means no cracks, otherwise I wouldnt worry.

Yes... that works, but. The question of who'll do the work is unsettled. I wont be able to, and I'm not comfortable putting an axe in the hands of one of the prime candidates. Drill, no problem, saw ok, chainsaw no.

With the tree right next to it, I can see the value of rebar. With masonry walls I guess I'll need to dig down round the edge for the wall. Frost dept h is about 45cm, so presumably need to go deeper. Unless I'm missing someth ing.
Re damp the plan so far is no built-in dpc, just bitumen the floor and inte rior of the 1st course of blocks.

What's the snow load for 4" & 6": with roof overhangs its 4.5m x 4.5m x 0.1 m x 200-300 kg/m3 for settled snow = 405-607kg for 4", 607-910kg for 6".
Half of 900kg on 4.5m of 2x4 gives 1" sag with clear spruce according to sa gulator. A central support could be added to improve that, so 2x4 sounds qu ite workable.
Tim Watts     

fred wrote:

n > its own. Its likely going to be the strongest component anyway
Corrie on polystyrene might be better. I assume poly isn't robust enough to just lay between frame & corrie & screw through, leaving the timber frame on the interior side of insulation. So how to avoid condensation & rot?
Tim Lamb wrote:

I clearly need to read up on how it should be fitted. I didn't find any inf o of use on that site.
We definitely can't live with indoor rain, though if the roof could be pers uaded to act as a dehumidifier that would be very welcome - but only if it doesnt take the bulk of the indoor air to dew point, which I presume it wou ld.
Noise is a nonissue.
So in short a lot of questions remain, at least one of which only we here c an answer, namely whether to build block from day 1 or begin with timber. I wish it were more straightforward.
NT
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OK, that describes my passive solar house very well.

I did the house much better by using galvanised pressed metal beams, inverted J profile. Full width rigid foam paper faced panels drop into that and are held in with metal wedges. Much cheaper than OSB and much better thermally too.
The inverted J beams have timber rafters bolted to the top flange with the depth of the timber rafters providing the very minimal slope to the metal decking roof that goes on the top of the timber rafters.
Those inverted J beams will span 14' trivially.

No point in that timber structure at all. Makes a lot more sense to use the block walls for the roof beams to go on.

Yep.

Yeah, I don't like timber floors anyway.

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