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It's finally time. I've ordered a cheap metal shed, 8x6. As mentioned before it has to go on a driveway that's not level. I was thinking of building a floor frame and using levelling supports - I have found some decent options so that's fine, but I just read in the instructions for the shed that you can't sit it on pressure treated timber as it causes corrosion. So my thought now is to build the frame from pressure treated timber, put non-treated OSB on top and then I can bolt the shed down onto that. So what's the best way to protect the OSB? A bit of waterproof membrane fixed around the edges? Or paint something else on? If so, what?
The other option is a concrete base but since the ground slopes it'll have to be pretty thick and my rough estimate is about 900l in volume. This would mean ready mix concrete which might come at comparable cost, according to internet suggestions. It would make an ideal floor, but it means I would have to build the form and it would need to be spot on for when the delivery arrives and any mistakes would be hard to fix. It would also be much harder to remove in the future if it were ever needed. This seems more stressful at the moment even though the results would be better.
Building my log cabin shed on Friday, mine going on top of 4 big concrete joists raised up on 2ft pillars of concrete, one at each end and a central one. This pillars were poured in some old plastic containers from work and have a rebar reinforcement inside.Â
This was done for similar reasons, levelling off the area and avoiding a 3.6 by 2.4 m slab 2ft deep pour of concrete.
Planning to have a damp proof membrane between the joists and shed floor
Is there a floor to the shed itself? Is the manufacturer worried about the preservative causing corrosion or just the fact it's resting on wet wood?Â
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Planning to have a damp proof membrane between the joists and shed floor
Might not do any harm, but I'm not sure it's necessary.
We have a problem with ours that the manufacturer specified a flat level concrete pad, so that's what we had put in (20ftx12ft). Unfortunately that means the nominally sized shed isn't quite that big (it includes the corners of the logs) so water runs down the sides and seeps under the pressure treated timber base. Which means its very damp under there and I had to take the floorboards up and add a layer of impermeable insulation to stop the moisture getting into the shed itself (it made the rubber gym flooring lethal as it just slid across the floorboards! And made the underneath of furniture mouldy).
Nothing I can do about it now with 2.something tonnes of shed on it, but at some point I'll have to jack the whole thing up from the corners and replace the floor. Â
What it actually needs is:
A) airflow to dry it out under there.
B) a better impermeable membrane under the floorboards.
Despite that there's no issues with moisture traveling up into the shed wall itself.
Sorry, delayed follow up that i intended to send immediately, due to power cut on site.
To OP any option to use joists to level off you slope in a similar manner? And does you solution need to also be the floor of the shed?
When i say damp proof, its basically only going between joist and wooden floor where it contacts, the rest will be open for airflow and i have a sacrificial 28mm treated strip of wood all the way round that would allow me to replace in the future without impact it shed itself.