Waterproofing a deck- making a room underneath

[UK4X4]

So I've been scribbling now for weeks and looking at a bunch of products/ methods.

1 waterproof decking - aluminum -Vinyl

relatively expensive- dont look as good as trex - or real timber

2 plastic-aluminum shields and drainage shoots

easy- a bit messy -lots of joins- plastic life ? or just use 20" aluminum flashing rather than the specific product
http://www.rainescape.com/Installation.htm

and just buy the downspouts

3 under joist systems-

multiple parts -failure points- expencive fill with snow and collapse ?


Has any one had experience of using any of the above ? my deck will have a roof over it- so just horizontal rain /snow will see it !


Or build a standard roof with slight incline 4" over 11' for example  10" joists 1/2" plywood or OSB
apply an EPDM membrane in 1 piece no joins

Then rip multiple  2x6's into a diagonal half. ie 2" to 4" deep over its length

and build a standard flat floating deck over the top of it. adding a EPDM gasket between the floating deck and the sealed roof.

Each batten would be tied to wall plate and positioned directly over the roof joists.

Each batten tied to the joist below at the end.

Copper self made soldered flashings at each post

Thoughts -input ?



Rough costs. 12 ft x 48ft deck

Gorrila decking $7 sq ft  $4042

Rain escape  
Quantity   Name   SKU   Each   Total
Rain Escape 12' Trough
RE12Tr   $26.99   $863.68
Rain Escape Caulk
REClk   $9.12   $91.20
Rain Escape Downspouts
RESpout   $33.99   $1,087.68
Items closely associated to this item:
Rain Escape 16' Trough $33.99
Rain Escape Butyl Tape$43.76
Subtotal   $2,042.56

Aluminium system similar to above with U troughs between joists was 8K installed

1 off roll of EPDM is $ 400 plus shipping plus plywood and the extra 2x8's and plywood

[MushCreek]

I just got my latest copy of Fine Homebuilding where they showed an interesting technique. Basically, they draped EDPM between floor joists, allowing it to drape deeper at the eave and and shallower at the house end, creating a pitch out of level joists. One thing i really liked is that they put a rim joist that was deeper than the joists, with a gutter behind it, so it wasn't visible. Underneath, they put up a decorative ceiling made out of aluminum soffit to hide the EDPM. Another good idea was installing one of the deck planks with screws so it could be taken up to flush out the inevitable leaves. I'm probably going to go with your last option for mine, where I'll have an open sun deck above my main level porch. I am going to try to incorporate the hidden gutter, though.

[UK4X4]

I suppose the article is not online ?

I did think of that but the epdm would have to curve

ie you'll use more material at the bottom than the top- so the sheet of material would either have to curve, or you do little folds on top of each joist

0 fold at the edge and 2" fold at the wall side.

How did they do it in the article ?

It would certainly simplify things- and the epdm would be compresed with no movement- wear and tear at each joist

and no leak paths !

Update - to have a 4" drop at the eaves and 0 at the wall you need to loose 2.5" of the material at the wall acording to my friendly autocad program.

which basicly means doubling the material on each joist at the wall.

with a 4" drop leaves you 6" in the joist depth for a hidden gutter

Seems workable to me !

[Erin]

0 fold at the edge and 2" fold at the wall side.
How did they do it in the article ?

That's basically what they did in the article.
It was fan-shaped, with the wider end/swale away from the house.

It is online (for free even):
http://www.finehomebuilding.com/how-to/departments/master-carpenter/site-built-deck-drainage.aspx

[UK4X4]

OK perfect

he does it in sections rather than one long sheet, with joins over joists, so no folding-

but probably need to glue the joints to insure no moisture gets through !