How much slope is necessary on a water-tight deck for good run-off. I ‘ve had one person say 1 inch in 12 feet, but that doesn’t seem like enough to me.
Cam
How much slope is necessary on a water-tight deck for good run-off. I ‘ve had one person say 1 inch in 12 feet, but that doesn’t seem like enough to me.
Cam
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Replies
1:12 would be uncomfortable to sit on. Plumbing drain lines only have 1/4":12 and they flow well.
I'm sorry, I thought you wanted it done the right way.
He said one inch in 12 FEET, not one inch per foot. I thnik one inch over 12' wouldn't quite be enough. If the joists sag a bit you've got ponding problems.
In Mexico we have a word for sushi: Bait. [Jose Simon]
Feet ... inches ... I'm still working on the black diamonds ...
But I was right ... an inch per foot would be excessive.
I'm sorry, I thought you wanted it done the right way.
Edited 5/28/2005 11:39 am ET by Ed Hilton
Thanks for the input. The deck is on the leeward side of the house so I think I'll go with the 1/8" -1/4" per foot. Besides, here in God's country it rarely storms and the rainfall is minimal. 1 in 12, wew, I guess that would be uncomfortable.
Cam
Summerland, BC
Probably a dumb question but is sloping the deck at all a best practice? I've read pro and con - the con being that it's hard to have railings appear properly plumb. Seems to me that water is going to drain off the deck to the ground below and as long as the ground itself is graded away from the house I'm not sure that I see the problem ...
Without the slope pooling (puddles) can occur, and besides making the deck less pleasant after a rain, when the puddles evaporate it often leaves stains on the deck. These stains can be hard to get clean on a vinyl deck.
Cam
OK... I'll bite... when you say watertight do you mean something with a membrane over it, or a deck where the deck boards are butted so tightly together as to be 'watertight'?
a membrane
1/8" per foot is minimal, depending...it can still allow some ponding unless it is perfectly done and the joists never sag. Quarter twelve is better to shoot for. Any roofing product on the market equires a minimal slope indicated in their oroduct literature. Ponding water will alays void a warrantee. The wate will eventually find a way in.
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I've built several of these and usually pitch them 1/8" to 1/4" per foot. But as Boss Hog mentioned, care should be taken to achieve a consistent surface with no sags.
So my deck frames are always a bit heavy for the span and material carefully selected.
One inch in 12' might be OK, but you also want to consider the effects of wind-driven rain if the deck is located on the prevailing storm wind side of the house so you slope, flash and set below door threshholds accordingly.
1 to 144 just gives a smaller margin for error.
1/8" per foot is fine as long as that's the slope in whatever valleys you have. Typically there will be valleys to lead water to the corners where the drains or scuppers are, so make sure your flat-plain slopes are great than 1/8 per. If the whole thing is under pavers or wood decking/sleepers, I'd go with more slope... more is better
Just finishing a deck at 1/4 per foot. On an old concrete deck that was already at this slope. I'll send pics when all is done but....... 1?4 per foot seems to be fine. Even the railing seems to be fine. It is all in how it is viewed with relation with the deck.
A railing that is not in line with the deck will always be off.
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