How to waterproof under deck for storage?

angelahorn

Hello - I'd be grateful for your advice. I have a large area under wooden decking which is about 5' high and would like to use it for storage. I was wondering how best to waterproof it from underneath - I don't want to have to remake the top of the deck. At the moment it's 'standard' narrow decking planks with gaps of a few mm between each. I wondered if fixing corrugated roofing sheets (cheapest variety!) would be a suitable bodge? It doesn't need to look beautiful as there's trellis screening the under-deck area from the garden, and it doesn't need to be perfect, but I'd like to be able to store bikes and a lawnmower there.

Many thanks for your help :-)

Avoriaz

Have you considered buying a garden storage unit big enough for your needs and small enough to be sited under the decking?

Google "garden storage".

Norman_Castle

Onduline from Wickes may be a good option

timbim_2

Buying a structure to put in there will be a massive waste of money, since you've already got the structure provided by the deck. The major problem you're going to face is getting the slope in so that any water that comes through the deck drains away, so you'll probably need to construct something to get that slope. I'd probably use a few bits of 2x1 supported in three or four places on differing height, angled blocks to get the angle, and then screw the sheeting into that. I'd also cover the screw heads with a dab of mastik or silicone to prevent any leaks from there.

Of course if the prevailing weather is into this area through the trellice, storing the mower in there may not be a great idea as it will get really quite damp in strong winds.

angelahorn

Avoriaz wrote: »

Have you considered buying a garden storage unit big enough for your needs and small enough to be sited under the decking?

Google "garden storage".

It's a sensible idea for smaller spaces, but not for this one alas - it's about 4m x 5m so I think putting a ceiling on it would be far cheaper than buying anything.

Thank you though!

angelahorn

Norman_Castle wrote: »

Onduline from Wickes may be a good option

Yes, that does look sensible - the corrugation would presumably make drainage a bit easier. Found this online supplier which sells them a little bit cheaper, but I wonder if Wickes have any promotions coming up? http://www.eroofs.co.uk/shop/product.aspx?pid=4064&dept=74

Thank you !

angelahorn

timbim wrote: »

.. I'd probably use a few bits of 2x1 supported in three or four places on differing height, angled blocks to get the angle, and then screw the sheeting into that. I'd also cover the screw heads with a dab of mastik or silicone to prevent any leaks from there.

Of course if the prevailing weather is into this area through the trellice, storing the mower in there may not be a great idea as it will get really quite damp in strong winds.

Thank you - that sounds like a good idea. Good point about rain penetration.The sides are well protected mostly and the trellis is covered with plants, but there is one area with solid steps on one side and the house wall on the other which would be best protected against rain, so I'll focus on that area.

timbim_2

To keep it dry, it needs good airflow, so opening up the sides a bit if they're not on the prevailing weather side might improve things. Getting a decent slope in the roof and laying the sheets in the right order for the water to run down and not through will make the roof fine. I'd wait until after a decent storm before putting anything expensive in there, then see how dry it's stayed, just to be on the safe side.

For materials, work out what you need then ring round a few local builders merchants for quotes, probably work out much cheaper than the DIY sheds.