New shed advice for base and window please

Discussion in 'Landscaping and Outdoors' started by joelmb, Oct 1, 2013.

  1. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Yes, if not on slab.

    Mr. HandyAndy - Really
     
  2. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Er, really handy. Really Andy.

    Not really handyandy.

    Just Handy-Andy-Really  ?????
     
  3. joelmb

    joelmb New Member

    Blimey guys, even without bearers and base timbers, the concrete slabs alone are going to cost new £2 each and for 7' square thats 28 so nigh on 60 quid. Had no idea there would be so much cost involvced on top of the shed (well, under it). Cant find any freebies/recycled going anywhere. The concrete posts are just if not more expensive that paving the whole area....

    Could I get away with just six slabs to place the bearers on? Wouldnt the base frame strengthen the t&g floor sufficiently?

    Actually, I'm getting a bit confused, do I need concrete base, then bearers, and then base on top of that, then shed on top of that?? Starting to look a bit like a game of Jenga if so lol.

    Thanks for your patience, theres me thinking this was a straightforward cheap project
     
  4. Joel, do you actually have this shed yet? If so, have a look at what's under the floor and report back, please.

    As Mr Ha says, there's bound to be 'something' there (or else your T&G floor would roll up...) and we need to know what size they are. That will help with any decision.

    That's a decent quality shed, and you shouldn't compromise on its installation.

    Timber posts in the ground will rot before the actual shed will. Are you planning to move in around 10 years?!

    Whatever method you end up using, any timbers underneath need to be kept well away from ground contact and isolated using some DPC where they do touch whatever base you use. There also needs to be a gap under the floor so's air can flow to keep the timbers dry under there.

    You certainly can use the 'slabs-on-sand-bed' method, but it needs doing properly, and so you need to be confident that the ground won't move below it - which it will unless you dig it out enough and add some hard-core first. A moving base risks distorting your shed, making doors stick and the floor spongy...

    I think my preferred method would be to dig some neat post holes - ooh 6-8" diameter - deep enough so's the ground feels more solid. That could be a foot and a half deep easily, if not more. But could also be less.

    Get any rock 'n' rubble you have handy and then mix some batches of concrete (aggregate and cement in a weakish mix - 5:1 I think, but check).

    Fill them holes by adding a bit of concrete, throwing in some rubble in between, tamping it down, a bit more concrete etc etc. Finish at the top by making sure the concrete is taken comfortably above ground level, tho' only around 3" inches are needed - use a round former as shown in your link above to make it neat.

    You will need, I reckon, 5 such posts - one in each corner and one in t'middle. You can vary this number, tho'; more posts mean thinner joists will be needed.

    (The corner ones will be positioned so that the joists which will be laid on a frame above it will run inside the outer shed skin - yes, you don't want any water running on to the tinber underneath.)

    Obviously, you will have made all these post tops dead level, an easy job.

    Then you'll need to build a supporting frame for the shed. Simplest way is to run a couple of main bearers down the outsides, and then sling cross bearers between them held by cheap joist hangers (less than a squid each). Size of timbers? I dunno - 6x2 for the two mains, and 4x2 for the cross? Others will no doubt advise on this!

    Obviously this is going to raise the whole caboodle a good 10" off the ground.

    Or, go your 'slab' route. Even with this method, I'd be tempted to lay cheap bricks at regular spaces on the slabs - with a piece of DPC on each - for the floor bearers to sit on. Keeps it completely off the damp ground.
     
  5. joelmb

    joelmb New Member

    Great comprehensive answer, thanks! Not received shed yet as only just ordered yesterday so cant tell you what underside is.

    Posts sound best as I'm not confident about ground shift/sink as there's a tree directly adjacent that I've cut back to site the shed as its only place it can go. (This might be a mistake?!)

    Few questions, are the concrete posts best topped with dpc before the timber bearer is placed on top? How is the timber best attached to the post tops? Finally what would you guestimate your solution is going to cost in materials?
     
  6. joelmb

    joelmb New Member

    Ok, so I'm guesstimating the total material costs of building a decent base and bearer frame from all thateverybody has said is going to be probably 100-150 quid then two men labour on top. I've come across this solution ust now which on the face of it costs an equivalentto the concrete type solutions (its £113 for 7' x 7' area) but has far less labour involved, and it seems to provide an equal load bearing area. Plus I like the fact it isn't permanent and could be re-used if we moved the shed, say. And it's a lot 'greener' I guess.

    Anyone have an opinion on them?

    Edit sorry forgot link now above
     
  7. Sean_ork

    Sean_ork Screwfix Select

    that's quite a good idea, make sure you lay some membrane down below it to stop weeds growing through

    if you wanted a proper green shed you'd be collecting old pallets and building your own ;)

    [​IMG]
     
  8. joelmb

    joelmb New Member

    i like it! bit drafty looking though ;)

    Yep membrane. I take it I would still need bearers if went the plastic base route would I?
     
  9. Yes, a nice 'solution'. Except it isn't a solution

    'Cos you still have to make sure the ground is absolutely level and firm enough not to move. "Prepare a well compacted levelled area for your plastic shed base..."

    Which I presume means digging out a layer of soil and compacting down some hardcore? Just as you would have to do for the slabs. So, £113 for what is effectively 'slab-replacement' sounds pricy to me.

    Unless I've got that wrong.

    The concrete post method? 10 bags aggy and 2 bags cement - £30? And then around 4m 6x2 and 8 or 10m 4x2 - that should be around £40? (Have a look on eBay too, and see if there's any being sold near you - you can pick up 2nd hand timber for next to now't). Joist hangers - £10. And a bag of nails...

    To answer your other Qs, you'd place a piece of DPC (a 100mm-ish wide plastic strip which is used in building) on top of the concrete post and sit the joists on top. That's it. I don't believe you'd even have to fix the shed down. (Most garden sheds just 'sit' there under its own weight - have you ever seen one fly?)

    By all means - if your ground is pretty firm at all times of the year - you may get away with removing just a skim, pouring over a few bags of aggregate, tamping it down, then a thin layer of sand - tamp down - and level with a length of timber, slightly rough the surface and lay concrete slabs gently on top. If the bed is firm, they'll likely only move a teeny bit over time, so your shed will 'absorb' this. The slabs can even have large gaps between them, which will help drain away any surface water.

    For the cost of bricks (unless there's a cheaper alternative?), I'd still like to add something that will then hold the timber floor bearers clear off the slabs, and you'd still place a piece of DPC between this spacer and the timber.

     
  10. joelmb

    joelmb New Member

    Once again, a brilliantly detailed reply thank you for taking the time! The pricing up is also so useful. £70 doesnt seem all that hard to swallow. By the way as you asked, I had this response regards the floor underside which is by sounds of it just batoned "The floor joists are the same thickness as the walls which is 1''
    1/4 square  (35mm x 35mm) with rounded edges. There is usually is 6 joists spread equally apart with an approx spacing guide at 35cm.
     
  11. joelmb

    joelmb New Member

    What lengths would you say should the 6x2 lengths and 4x2 cross pieces be cut to? I've no idea what sizes they'd be supplied in. Or do I just ask for 4metres and 10 metres of? Lol any more help and you'll be building it for me ;)
     
  12. Hopefully a builder/chippy on here will first confirm that the joist sizes I've mentioned are ok. It may be that the 6x2s aren't needed, just 4x2 all round (especially with a centre cross rail which will sit on a middle post to take the centre floor weight.

    If you go to a timber yard (builders merchants) they should have this timber in standard lengths usually going in 300mm steps - 3.6m, 3.9, 4.2 etc. You then choose the best fit - in this case 4.2m, which - when cut in half - should do the job.

    So, once you've designed your frame, you figure out how many you need.

    If you go to a place like Wickes, I doubt you'll get 4.2m lengths, so will have to plumb for 2.4m pieces (the nearest usable size).


    (The battens already on your floor are thin - they're just to hold the floor together and keep it off whatever surface the shed is sat on.)
     
  13. joelmb

    joelmb New Member

    Thank you you've been really helpful I'll let you know how it all works out shed arrives in a fortnight apparently been told today
     
  14. Ray Retired

    Ray Retired Active Member

    Do folk not use railway sleepers any more for this kinda thing?

    There's an auld shed and a greenhouse on my allotment taking no harm sitting on sleepers, been there 30+ years and look no worse for it.
     
  15. chippie244

    chippie244 Super Member

    A sleeper is going to cost £25-£30 each.
     
  16. Ray Retired

    Ray Retired Active Member

    In old money that'll be two bob each and the price of a few pints for the man with a horse n cart.

    Last I heard, railtrack was ripping up the wooden track supports and replacing 'em with concrete sleepers from the USA.

    Would have thought they'd be an abundance of the bitumen soaked back breakers around nowadays.
     
  17. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    It's time to stop faffin about.

    DPM, 16 slabs, 8 3"x2" tmber bearers, done.

    Mr. HandyAndy - Really
     
  18. joelmb

    joelmb New Member

    Reason we're "faffin" is that using slabs is, for me at least, cost prohibitive so seeking the cheapest yet effective long lasting method which on face of it the concrete pillars provide. Thanks for suggesting 3x2 though, you think these should suffice?
     
  19. The only way 3x2s will work is as 'bearers' and not as 'joists'. Bearers will be fully supported along their lengths by the slabs or whatever underneath; joists will be supported at 'points' and need to be sturdier.

    4x2s should be ok.

    Where abouts are you? Have you looked in your local paper/ gumtree/ ebay/ etc to see if there's stuff you can pick up for next to now't locally?
     
  20. Sean_ork

    Sean_ork Screwfix Select

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