Sectional Concrete Shed

Discussion in 'Engineers' Talk' started by paulds117, Nov 20, 2020.

  1. paulds117

    paulds117 New Member

    I've recently had built a sectional concrete shed, replacing an old cheap wooden one that after years of neglect destroyed everything that I'd stored in there. The original plan was for a workshop/office, since the Mrs is taking a dim view of me building control panels on the kitchen table.

    A couple of weeks after the shed was erected, I was still seeing concerning levels of sweating and condensation on the sectional walls, and after the first few searches of horror stories of damp and metal rusting, I knew I needed to do something.

    From the posts here and elsewhere, I've managed to gather enough information to put together a plan to line the shed correctly, which I'm currently implementing. Since this forum was such a help, I'll post here what I've found and what I've done, In case this information is useful to someone else in a similar position.

    Firstly, the fixing brackets. As you probably know, its not recommended to drill into the concrete panels. (no, I didn't know either till I started to research online). The shed companies will sell you fixing brackets at an extortionate price, but I re-tasked some galvanized jointing plates (35x97mm), drilling a new 7.5mm hole for the roofing bolts that hold the panels together, 20mm from the edge. Bending the plate to match the angle between the angled edge of the concrete panel and the baton. As per the picture.
     

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  2. paulds117

    paulds117 New Member

    This allowed me to build the frame around the interior, approximately 25mm away from the surface of the concrete panels. The batons are Wickes, treated Kiln Dried C16 45x70. The screws used are 40mm decking screws. All I did was remove the square roofing nut and washer from the panel interlocking bolts, and slide my modified bracket on, replacing the washer and square nut. As I'm not intending on mounting much to the walls, I've skimped on the batons, and have installed the brackets every other panel. The top and bottom struts are made with 25x38mm treated timber, also from Wickes, and mounted to each of the uprights, there are 3 galvanized angle brackets to hold the insulation in place, (33x25mm (20034 Screwfix)), set back 50mm.

    This gives an average of around a meter between the batons, which worked quite well for the insulation, and including the corners gives four posts per wall for a 10x12 foot shed.

    The corner pieces however were an issue which I'll detail on the next post.

    The wall insulation used was sourced from Wickes is polystyrene 2400x1200x50mm. The floor insulation is 2400x600x25mm. I laid out a DPM on the concrete slab before laying the insulation, again the Wicked 1000 gauge 4x3M DPM. I could tell the story about how the 6 DPMs and 1 pieces of floor insulation arrived but I'm sure I'm not the only one to bugger up an order.
     

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  3. paulds117

    paulds117 New Member

    In the corner pieces, the retaining bolts were only through the North/South direction, which made it difficult to use the batons. There was a large discrepancy between the surfaces that I couldn't run a wall across, so I used two pieces of 25x38, fastened together and fixed to the 45x70 get the square angle I was looking for. The difficulty was fastening the baton to the plate, which I had to manage with a 6" ratchet and screwdriver bit (purple screw on the drawing).

    A cutaway drawing is below. all four corners are like this, along with the modified jointing plate (Red) and angled brackets (green) holding the insulation (Blue).
     

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  4. paulds117

    paulds117 New Member

    So, so far this gives us the internal frame and insulation, as shown on the picture.

    Note, the lower pieces of the frame are sat upon the 25mm insulation which is sat upon the DPM, so they're raised off the concrete slab base.
     

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  5. paulds117

    paulds117 New Member

    The next step is the vapor barrier; which again came from Wickes. (the entire setup is either screwfix or wickes). I bought 20M of vapor barrier, which i stapled around the room. There was enough left over to cover the floor, even though it already had a DPM sheet over the concrete slab, but I thought why not, just in case any sharp bits of concrete had punctured the DPM.

    I covered the joins and staple holes with foil tape, as seen below. this was trickier to do than I thought, as there are a few unintended folds and snags in the vapor sheet.
     

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  6. paulds117

    paulds117 New Member

    Finally, a load of OSB for the walls and floor. I'm still in the process of fitting this so you'll have to forgive me. I've used 9mm Wicked OSB throughout, and I'm intending on fitting a cheap laminate to the floor and painting the walls.

    It's nice and cozy inside so far, but i guess only time will tell. I'll continue to update till I'm finished, and I'm more than happy to answer any technical questions on the build.

    Paul
     

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  7. Bob Rathbone

    Bob Rathbone Screwfix Select

    Looks like you have it covered, nice job. You will need some ventilation, probably best at a time when you don't use the shed, then the cold fresh air won't bother you.
     
  8. paulds117

    paulds117 New Member

    There's a fair bit of ventilation already through the gaps between the corrugations of the roof, although I'm wondering whether to add more.
     

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