We will have a fiberglass surface install on our deck.
Deck is 8ft x 16ft. I am planning on using 2×10.
I was told to get a 1/4in slope per 1ft depth of the deck.
What is the right way of building the top slope, so rain and snow move away from the house ? The slope will be on the 8ft side of the rectangle.
Creating a ledger that has an angle and follow with regular joist 16″ o.c. ?
Or create a cut on the length of the lumber to remove the angle?
Any pointers?
Thanks again,
Ben
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Replies
1/8" slope should be enough for a smooth surface. Too much slope will make it slippery when wet. Set one side of the joists higher than the other.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
There is a reason he was told 1/4" per foot. If this is to perform as a watertight roof it must shed water. At 1/8" pitch it will have puddles.
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I'm going to take a stab at this--I'm not sure I understand what you are saying, but...
The 16' length runs with the house (i.e., the legder board bolted to the house is 16' long), correct?
You will be running joists from the ledger to a rim joist, and these 8' long joists will be 16" o.c., right?
I would not do anything to the ledger board to try to get the pitch you need. Just make sure that it is through-bolted through the house--not nailed or lag-screwed. Make sure it is properly flashed to shed water, so no water gets into your house. Many people advocate using some sort of spacers to hold the board away from the house a bit to allow an air space, while some don't.
If you want a quarter inch pitch per foot, over the 8 feet, you are talking a 2" drop--which to me says the top of your rim joist that the joists butt into should be 2" below the top of the ledger. I would cut the proper angle on the ends of the joists, making them very elongated parallelograms. In other words, their ends will not be plumb cut (ends 90 degrees to top and bottom edges).
I don't think using wedge-shaped shims on the ledger or at the ends of the joists would work. Don't know if you were even considering that. I guess it bothers me that if you use joist hangers, the bottom edge of each joist will not rest flat in the joist hanger, but I don't know of any way around that.
Maybe someone else has better advice. If you were to shim out the top of the ledger so the whole top of the ledger is gapped away from the house (and the bottom tight), I just see that as a place for junk to collect and then the rim joist would also be tilted outward at the top and then that would create a whole new set of problems.
Maybe I am overthinking this. To be honest, when we built decks we made them level and let the water (we hoped) fall off between spaces in the decking.
Thanks for your answer ! You are right : The 16' length runs with the house (i.e., the legder board bolted to the house is 16' long), correct? - YES EXACTLY -You will be running joists from the ledger to a rim joist, and these 8' long joists will be 16" o.c., right? - YES EXACTLY -Making them very elongated parallelograms : That sounds good !I am just a bit nervous about the hanger not supporting flat too...Any advice for the hanger part ?
I am just a bit nervous about the hanger not supporting flat too...
But it will. Cut the ends plumb, then cut a level seat on the bottom of the joist. Or buy a high-dollar simpson hanger with an adjustable seat angle.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Edited 7/7/2009 10:18 pm ET by FastEddie
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"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
You got the description right and the word wrong: , their ends will not be plumb cut (ends 90 degrees to top and bottom edges).
You meant to say the ends will not be square cut. The ends WILL be plumb cut, which makes the joist a long parallelogram, not a rectangle."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Right you are! I was thinking a level deck and 90 degrees, plumb cut, but, of course, the whole issue is that this deck is not level--so I guess the joists will in fact be plumb cut, but not level--much like rafter tails.
In any case, I can't see cutting little birds' mouths so the joists lay flat in the hangers, can you? I would think this would weaken them. Maybe shims of Vycor or shingles or something? EDIT: Just read your last post and see that you did propose cutting the joists to allow them to seat in the hangers--I guess Piffin's idea of adjustable would be best. I thought about that the joists wouldn't be sloped enough to bother--even with the "plumb cutting," but a slope of 2" in 8' is fairly noticeable. (I would think if dropping the joists 2" opens a wedge-shaped gap where the top is a quarter inch or less, nothing would need to be done, but much more than that....)
Edited 7/8/2009 7:55 am ET by Danno
I would cut a flat on the downhill end of the joist ... maybe ... and leave the uphill end full thickness. 1/4" sl0pe, on a 10" joist ... the gap can't be very much."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
wasn't me who mentioned adjustable hangers. I see no reason to consider the small amt of pitch when cutting the joists
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Yes, you are over thinking a bit. this low of a pitch will not need any angle cutting at the ends of the joists. Square is fine. They will seat in the hangers fine too.And the ledger to house connection should be getting flashed in with teh FG roof material, so stand off not even needed.
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