Garden Shed Underfloor Vapour Barrier

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red_xsi

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Master Geek

#198882 26-Jul-2016 21:04

Anyone have any experiences with wooden floors in garden sheds?

I am about to assemble my new she which has a built in wooden floor and was wondering about making it as resistant to rising damp as possible. Was thinking that either a vapour barrier directly on the ground under the shed or a barrier between the floorboards and the joists.

Anyone have any thoughts?

timmmay

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#1599252 26-Jul-2016 21:07

I had a vapour barrier put under my house, it made things much drier and smelled better. I imagine it would help a shed too.

mdf

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#1599255 26-Jul-2016 21:12

I wouldn't put it right under the floorboards. If your shed is anything like mine, sawdust, dirt, grass and oil will all be spilled in pretty short order. Joins in floorboards = handy dandy emergency drain.

On the ground would probably be fine, but it would have to be a pretty nice shed to make a difference. Most sheds leak somewhere between a little and a lot so I would have thought that would have been a greater source of moisture than any rising damp. What sort of soil is it on?

mdf

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#1599256 26-Jul-2016 21:12

And how far about the ground is the floor going?

red_xsi

120 posts

Master Geek

#1599279 26-Jul-2016 21:54

mdf:

I wouldn't put it right under the floorboards. If your shed is anything like mine, sawdust, dirt, grass and oil will all be spilled in pretty short order. Joins in floorboards = handy dandy emergency drain.

On the ground would probably be fine, but it would have to be a pretty nice shed to make a difference. Most sheds leak somewhere between a little and a lot so I would have thought that would have been a greater source of moisture than any rising damp. What sort of soil is it on?

Good point about the spillage factor.

It is a decent steel shed - proper wooden frame interior with louvre windows and clearlite roof panels etc. I am resigned to the fact that there will be some moisture but am wanting to minimise it if possible.

Soil has a high clay content.

Not 100% sure how far above the ground the floor will be as yet as I havent layed eyes on yet. I assume it will be a suitable distance as I am buying from a reputable NZ Manutacturer

mdf

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#1599287 26-Jul-2016 22:06

Some wooden floors kits suggest that you lay them on a concrete slab. If you're doing that and totally wanted to overkill it, you could put a moisture barrier under the concrete. Others let you mount them on your own piles. A reasonable air gap might be enough, but clay can be a right b*.

froob

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#1599299 26-Jul-2016 22:16

If you can, I would take steps to try and minimise the amount of moisture going under the shed, and treat a vapour barrier as secondary to this. For instance can you change the lay of the land so that water drains away from the shed, or install drains and/or a non-permeable surface around the shed?

If you're in an area where the ground is quite damp, the vapour barrier might still be a good idea even after taking those steps. Otherwise, you might find that the ground is quite dry anyway.

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