My 3.6 X 7 Meter build, have a base ready to go

[Fil]

This was going to be a slow project, but covid sped it up a bit. Dug out the hole over several weeks last year, ( around 2ft deep at the back and began filling with hardcore, from a garden path and some friends walls and building work. and once complete, will start the same again on the oposite side of the garden, with the use of office, bar, garden summer house type of thing.

Only came across one root from the willow, thats been removed, the root that is, not the tree.

Was never going to be done quick, then covid strikes and due to spending a lot of time in the garden my 4 and 6 year old, kept playing in the hardcore out of bordem, so got 12t of mot type one, used 9ish and made the area safer to them, roll on not spending anything on drink and eating out, in went some sand , dpc, rebar and 3.5M3 of pumped in concrete.

So now i have this 3.6 x 7m x 150mm base, below 30M2 but well within 1m of the boundrys, so is getting the suitable fireproofing, cladding in hardie or cedral board.

Would like a pitched roof, tho it will be low to keep under the 2.5m total height, so im not sure on total internal heights yet, and may have to go flat roofed to get the extra internal height?

Only just really played with sketchup in the last few days, but a rough guide to the two roof types,

Next stage it brick work, once I source a decent second hand UPVC door for the side for day to day access. Plan on making two large 1200mm wide doors the front, for potential vehical access if the need arises


Cost so far,
8, 3.6m 2x6 and 1, 4,8m 2x4, £88
12tons mot type 1 £336
large bag of sand £44
DP plast sheet roll £30
4, 3.6 x 2 sheets of rebar £84
rebar chairs £30
3.5M3 of pumped concrete £999.60

 

[Sheptonphil]

Excellent so far, going to enjoy this one as well.

Is it not worth getting planning permission to enable you to have extra height if you want it?

 

[Blackswanwood]

Looks good - seems like quite a few workshops have been moving forward during lockdown. The picture of your little helpers took me back to when mine were that young - all that grass but a hole full of hardcore is far more interesting at that age!

 

[MikeG.]

That looks like really nice preparation, with loads of making-up of levels. That was hard work!

Edit...

Why have you raised the reinforcing so high up in the slab depth?

As for the roof.....well, you already know which one is the more attractive. If you want to have clear headroom over most of the floor then its perfectly possible to design a pitched roof which doesn't need joist/ ties. A central principle truss and a structural ridge beam scarfed over it and you'll have all the headroom you could ever want.

 

[Fil]

Looks good - seems like quite a few workshops have been moving forward during lockdown. The picture of your little helpers took me back to when mine were that young - all that grass but a hole full of hardcore is far more interesting at that age!

It's money that's pushed this along for me, no holidays, eating out, pubs and clubs!

And their eyes lit up when a jumbo Bag of sand arrived

That looks like really nice preparation, with loads of making-up of levels. That was hard work!

Edit...

Why have you raised the reinforcing so high up in the slab depth?

As for the roof.....well, you already know which one is the more attractive. If you want to have clear headroom over most of the floor then its perfectly possible to design a pitched roof which doesn't need joist/ ties. A central principle truss and a structural ridge beam scarfed over it and you'll have all the headroom you could ever want.

Never counted the amount of wheel barrows full of dirt that came out, but just did a bit now and then,

The rebar was just below the mid point of the slab, sitting on the lower 65mm point of the chairs, tho it does look more like 10mm from the top in my photos.

And yeah I'm hopefull that I can get a pitched roof in and keep my heights, will look into design a bit more.

Excellent so far, going to enjoy this one as well.

Is it not worth getting planning permission to enable you to have extra height if you want it?

Planning was never an option or considered as didn't want a high pitched roof in the first place so 2.5meters was fine, only issue I forgot was including the slab, that's 100 to 150mm above ground level, so will loose some of my 2.5meter limit now.

 

[MikeG.]

.........The rebar was just below the mid point of the slab, sitting on the lower 65mm point of the chairs

Then it may as well not be there, I'm afraid. Structurally, it will be doing nothing at all. Reinforcing should be in the zone in tension (or which could be in tension). You've put it somewhere which can never be in tension.

Planning was never an option or considered as didn't want a high pitched roof in the first place so 2.5meters was fine, only issue I forgot was including the slab, that's 100 to 150mm above ground level, so will loose some of my 2.5meter limit now.

I don't think I've ever come across a case of a shed being measured by Planning Enforcement. If it were, all they would ask you to do would be to apply for retrospective permission.

 

[Fil]

Doh then! Was told ( tho i may have got it arse about face ) by a builder that it needs to be 2" from the bottom to mid point of a 6" slab.

Should it have been 2" from the top?


tho too late now

 

[Sheptonphil]

I don't think I've ever come across a case of a shed being measured by Planning Enforcement. If it were, all they would ask you to do would be to apply for retrospective permission.

Planning enforcement came and measured my shed last month ‘concern’ raised by neighbour.

 

[siggy_7]

Doh then! Was told ( tho i may have got it buttocks about face ) by a builder that it needs to be 2" from the bottom to mid point of a 6" slab.

Should it have been 2" from the top?


tho too late now

I think that is in the right place - reinforcement goes towards the bottom of the slab for reinforcement, since that is where tension builds when under high loads. If it's mainly for crack control (not structural) then it goes near the top. The mid thickness point of the slab is its neutral axis (neither in tension or compression when under load) so for structural reinforcement it needs to be below this line to be effective.

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[MikeG.]

Doh then! Was told ( tho i may have got it buttocks about face ) by a builder that it needs to be 2" from the bottom to mid point of a 6" slab.

Should it have been 2" from the top?


tho too late now

I think that is in the right place - reinforcement goes towards the bottom of the slab for reinforcement, since that is where tension builds when under high loads. If it's mainly for crack control (not structural) then it goes near the top. The mid thickness point of the slab is its neutral axis (neither in tension or compression when under load) so for structural reinforcement it needs to be below this line to be effective.

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You missed the point. It IS in the middle. In clay areas, it is put in the top and the bottom because clay heave can bend the slab upwards.

A 6 inch slab is difficult to reinforce because of the cover needed (25mm min) and the pointlessness of putting it in the middle. That gives you a zone between 25 and 40 or 50 up from the bottom in which to put the reinforcement. Twenty five mm up from the bottom is hard to achieve because of the bendiness and curviness of the grids. A 100mm slab is all but impossible to reinforce properly.

 

[siggy_7]

The OP said the reinforcement was 2" from the bottom of a 6" slab, i.e. about 1/3 the way up? It would be better sitting slightly lower I agree, but if it is an inch below the middle as I have interpreted then it will be doing some good.

Edit: I was going on the post where he cited advice given to him by a builder, assuming that reflected what had been built. If the reinforcing is higher than this then agreed it is of limited utility.

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[MikeG.]

The OP said the reinforcement was 2" from the bottom of a 6" slab, i.e. about 1/3 the way up? It would be better sitting slightly lower I agree, but if it is an inch below the middle as I have interpreted then it will be doing some good.

No, he said this:

......The rebar was just below the mid point of the slab, sitting on the lower 65mm point of the chairs.......

65mm up in a 150 slab is 10mm from the centre line.

 

[Fil]

No progress as such, have roofing/ building membrane, insect wire mesh, some 90mm framing nails, lots of screews, dpc and my bricks turn up next tuesday, 2 courses palnned, as slab, at its lowest point is 100mm above the grass / ground level. Still searching for a suitable door.

As for the roof.....well, you already know which one is the more attractive. If you want to have clear headroom over most of the floor then its perfectly possible to design a pitched roof which doesn't need joist/ ties. A central principle truss and a structural ridge beam scarfed over it and you'll have all the headroom you could ever want.

So talking of roofs, im looking at a very low pitch ( have worked it out to be just over 5 degrees ) and im looking at a metal box section sheeting covering, as its suitable for a min of 4 degrees, https://www.cladco.co.uk/32-1000-box-pr ... -polyester

so from the top of the frame 2x4 at a height of 2200mm, ill have 300mm to fit my roof in.

Im looking at a 2x8 ridge beam of 7 meters long, ( likely two pieces joined )

With 2x6 rafters @ 400mm.

And then would i need joists, that also sits on the top of the frame, again at 400mm centres, 2x6.

Would i need any osb boarding? and if so does it make a differeance where it goes? on top of rafters, or below them, or even below the joists, to make the internal roof flat?

couple of poor sketch up pics, to hopefully aid what im looking to do.

 

[MikeG.]

I've only a second........

You don't need a ridge beam if that is your proposed truss design. If you would find a ridge board convenient for properly locating all the trusses, then use a piece of 6x1.

 

[Hornbeam]

I seriously recommend you have a rethink about the quality of profiled steel you are using for the roof. Polyester is only a 25 micron thick paint system and scratches really easily, the substrate will be a plain galvanised steel. You will get no guarantee (with any meaning) and I would expect to start see corrosion at the sheet ends within 5 to 10 years.
A 200 micron plastisol is a much more robust coating and wont be that much more but be aware there are plastisols and plastisols. The differences appear quite small but its a bit like DNA, humans are 98% the same as chimps but we are quite different.
You have shown sketches of the roof structure but not sure where you are putting the insulation.
If you are using a fully supported steel roof then you will be OK with 0.5mm but if spanning it across purlins or battens go for 0.7mm which should span around 1800mm dependent upon actual gauge and the profile
How are you getting daylight into the building are you having windows or have you considered an insulated roof light
Ian

 

[Fil]

I've only a second........

You don't need a ridge beam if that is your proposed truss design. If you would find a ridge board convenient for properly locating all the trusses, then use a piece of 6x1.

Ill come back with a more final design, but if i can leave out a ridge beem i will, thanks

I seriously recommend you have a rethink about the quality of profiled steel you are using for the roof. Polyester is only a 25 micron thick paint system and scratches really easily, the substrate will be a plain galvanised steel. You will get no guarantee (with any meaning) and I would expect to start see corrosion at the sheet ends within 5 to 10 years.
A 200 micron plastisol is a much more robust coating and wont be that much more but be aware there are plastisols and plastisols. The differences appear quite small but its a bit like DNA, humans are 98% the same as chimps but we are quite different.

You have shown sketches of the roof structure but not sure where you are putting the insulation.

If you are using a fully supported steel roof then you will be OK with 0.5mm but if spanning it across purlins or battens go for 0.7mm which should span around 1800mm dependent upon actual gauge and the profile

How are you getting daylight into the building are you having windows or have you considered an insulated roof light
Ian

Im open to other manufactures if you can link to any with a thicker coating? It was not something i even looked at, just read it scratches easy, I looked at various materials and this was the only one that i found that can be used down to a 4 degree angle ( im going have just over 5 )

Im not sure myself where the insulation is going, or what type im using yet? more a case of when im at the point see what about as in leftovers online, if none get the best valve for money new.

Asd as for 0.5 or 0.7, the costs for the thicker wasn't worth not going for, as not a great deal more.

Will have a window on the side, maybe two. but its in a fairly shaded area at the bottom of the garden most of the time, so will have plently of lights fitted inside.

 

[Hornbeam]

A 200 micron plastisol is fine just as I said there a huge variation, Some manufacturers provide full rectification guarantees for up to 40 years (commercial buildings only) Some offer guarantees but when you read teh small print arent worth the paper they are written on. 4 degrees after deflection is the generally accepted minimum pitch for through fix trapezoidal sheeting, Some manufacturers provide guarantees down to 1 degree and also cover roofs like barrel vaults where the very top is effectively 0.
Dont think thicker is always best. Thicker sheets of the same profile will be stiffer and span further bu the cut edge of a sheet is the most vulnerable to corrosion. Generally the steel will have a zinc or zinc alloy layer which provides sacrificial corrosion protection for the steel. The thicker the steel the less protection is provided. Zinc alloy coatings provide much more cut edge protection than plain zinc