TW Builds a Garden Room

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  • I'm finally getting round to building this, and think I'm done with the design.

    It's roughly 3.5m x 5m on the outside, with an office on one side, and a shed on the other

    To stay within permitted development, it will be 2.5m high at the highest point, with a 1.5 degree pitch.

    It's mostly going to be timber framed & clad, with aluminium bifold doors on the office, and aluminium framed roof & rear windows.

    I say mostly, as I may have a steel frame for the door opening, so that there's no door problems caused by expansion / contraction of the wood.

    The foundations will be 300mm diameter x 600mm deep reinforced concrete pilings, and the floor frame will sit on adjustable pads.

    The office floor will be insulated with 100mm PIR, chipboard, then various layers to give me underfloor heating.

    The shed floor will be t&g chipboard, then a 5mm rubber mat.

  • First things first, removing the old shed (and moving all the crap in side it into a storage unit)

    The old shed was freecycled, and now live in North London somewhere.

    The cat still lives here, but has lost a bed.

    Then it's ground clearance time. After moving a load of paving, Ive discoved at least three separate concrete pours, all of very poor quality (meaning I only need the breaker on a couple of occasions), and 4 very deep concrete posts.

    I also found a lot of waste metal, and old radio wrapped up in tree roots, an intact pot of poster paints, and a load of smashed windows.

    Skip bags were initially the best option, but as I have discovered, I need to get rid of far more waste than I initially thought, so next week will be getting a skip.

  • Cant see the images

  • Earlier last week, I start digging the foundations, as I'm getting bored of just clearing stuff.

    Each footing is reinforced with 10mm rebar

    After two pours, I'm sitting on my hands, because the weather is rubbish.

  • Ok now?

  • All good

  • I need to get rid of far more waste than I initially thought

    I feel your pain

  • old radio wrapped up in tree roots


  • What sort of budget are you working to?

  • It's going to get its revenge someday.

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  • If it's going to be timber with 100mm PIR, have you considered SIPs? The build will be much faster and you'll get less coldbriding from studs and screws interrupting the insulation.

  • SIP construction isn't something I'd really considered, to be honest.

    The difference in u-value between a SIP wall versus timber & PIR wall seems to be negligible or worse, depending on which manufacturer site you look at.

    Moving big SIP boards would be a challenge too, given the access I have.

  • Great looking project.
    Should be deadheading your Hydrangea now too.

  • Timber & PIR numbers are likely to be optimistic, based on the performance in the middle of a sheet with no metal screws inserted. Every stud is a reduction in insulation thickness. On the other hand, the metal window frames are probably a bigger problem in terms of heat.

    A single SIP is probably about 50kg, so ease of build without a crane depends on how close to the delivery truck can drop them. Having all the openings already formed to the correct sizes is nice to avoid too much faffing with shimming frames. I've seen projects where the manufacturer basically did first fix before delivery, though that's less helpful for a shed. At 3.6 x 5 with a mostly-glass fourth wall, there'd probably be less than 20 pieces to make the entire shell.

  • I've not fully costed it yet - I'll do that when I've made a proper wood / cut list from the plans.

    Biggest items are doors (2k), roof window (1k), timber (1k). insulation (1k) and cladding (2k)

    You can probably add 2k for tools, although I hope to get back £500 for the nail guns alone.

    Finger in the air is about 12k, compared to >20k for shop bought.

  • Should be deadheading your Hydrangea now too.

    It's on the todo list. I've already taken out all of the dead woody bits.

    Not sure what to do about the crab apple behind it, though, as it's budded & starting to blossom. Annoying, as I'd planned to prune it back this year, but the season started way too early.

  • Watching this thread with interest, any chance of have a closer look at your model? SketchUp I assume?

  • Did I send you the sketchup file? PM me an email address & I;kk get it to you if not

  • Update time!

    I finished all of the groundwork before coming into lockdown, and was then hit with the problem of no wood being available from anywhere.

    I had the timber that I needed for the floor frame, but didn't fancy leaving it out in the elements, without any idea of when I could build it up more.

    Now that timber yards have opened up, floor framing has commenced.

  • Picture time.


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  • Concrete

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  • Wood

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    • IMG_20200614_123753_50.jpg
  • The concrete footings were pretty difficult to keep level, although I did manage to keep them all within 10mm and the base pads have double screws, which allow for up to 60mm of height change - I used a water level to re-level once everything was squared up

  • Digging the foundation down 20cm has given me headache about what to do with the perimeter path - it needs to be supported, but not look rubbish

    The concrete blocks are a temporary measure, and will probably be replaced by sleepers, secured with spikes.

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TW Builds a Garden Room

Posted by Avatar for TW @TW