Riser Material..I need to go light. - AVS Forum
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post #1 of 16 Old 01-04-2007, 03:01 PM - Thread Starter
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Im trying to think of ways to cut down on weight for my riser. I need to use 2x10's unfortunately to properly view the screen so I was thinking maybe I could go with something lighter for the floor of the riser instead of what seems to be the standard of 3/4 inch plywood.
Would half inch plywood still work fine? Or is there anything that I could use to save on weight?
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post #2 of 16 Old 01-04-2007, 05:21 PM
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Instead of the solid 2x10's, you could use fabricated joist to cut some of the weight. I wouldn't use anything less that 3/4 ply, which in my opinion is still not thick enough for the deck. My risers didn't stop sounding like a drum until I added the third layer of plywood (3/4" - 1/2" - 3/4").

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post #3 of 16 Old 01-04-2007, 06:06 PM
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*knock on wood* Thankfully, my riser doesn't have a drum sound/feeling to it, and it's 2x12 with 1 sheet of 3/4" ply and 1 sheet of 5/8" particle board. I did carpet over it, though, so that might help a bit.

I like Winkelmann's idea of using engineered joists - all the strength with a lot less weight. Don't skimp on the topper; you don't want your riser to bow when you park a bunch of weight on it.
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post #4 of 16 Old 01-04-2007, 06:34 PM - Thread Starter
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Enginnered joists meaning ones I build myself out of 2x4's..sorta like 2 walls laying flat with a bunch of 2x4's cut to 6 inches to seperate the two? Or are these prefabbed joists (ibeam) that I see a lot of in houses..I think they look like plywood sandwiched between 2x2's? If so, think home depot would have them?
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post #5 of 16 Old 01-04-2007, 06:43 PM
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Just thinking out loud. Could you make a series of metal stud 9 1/2 inch walls out of metal framing material? Would be a lot lighter than wood. with the studs spaced 12 inches apart and the "walls" spaced 12 inches on center it would still be a lot lighter than wood and you could use the savings to use 2 layers of decking and a layer of roofing felt in between.
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post #6 of 16 Old 01-04-2007, 09:00 PM
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Why is weight a factor with the riser?
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post #7 of 16 Old 01-04-2007, 09:43 PM - Thread Starter
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My theater is on a second floor and underneath is a very large great room/dining room/kitchen with no upright supports.

I was told 40 lbs per sq foot is the load of the upstairs floor but im just paranoid. I figure the riser with plywood to be 250 lbs? plus 3 chairs, at 225 pounds, plus 3 people at 600 lbs..1075 lbs over an area thats 10x5..I guess it can support 2000 lbs of weight. There will be another row of 3 chairs plus 600 lbs more for people a few inches in front of that as well, but i guess that adds another 35 square feet to about 900 lbs.

Seems I'm well within the weight limit but I'm very paranoid is all.
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post #8 of 16 Old 01-04-2007, 10:49 PM - Thread Starter
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I ended up going with 2x10's.
Ill get to the subfloor this weekend. I'm not too worried about deadening the sound or stopping vibration. Insulation plus carpet is a-ok with me. If thats the case can I go very thin with my subfloor (not really subfloor but the the floor of the riser rather)..1/2 or maybe 5/8ths? Ive even read somewhere you can do 7/16th's OSB.
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post #9 of 16 Old 01-30-2007, 12:54 PM
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Quote:
Originally Posted by geekysteve View Post

*knock on wood* Thankfully, my riser doesn't have a drum sound/feeling to it, and it's 2x12 with 1 sheet of 3/4" ply and 1 sheet of 5/8" particle board. I did carpet over it, though, so that might help a bit.

Did you apply the carpet to your riser yourself? If so, what method did you use, especially on the corners?
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post #10 of 16 Old 01-30-2007, 01:04 PM
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I just used an electric staple gun to attach the carpet and used a carpet knife to cut the corners. I was really careful and you can't really see the seem on the corners unless you are looking for it.
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post #11 of 16 Old 01-30-2007, 02:32 PM
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OK. So on the corners, you just cut a slit diagonally or what? Did you have to fold the cut flaps in on themselves to keep the cut edges from fraying? Also, did you use any carpet padding?
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post #12 of 16 Old 01-30-2007, 03:04 PM
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Quote:
Originally Posted by Tapiozona View Post

I was told 40 lbs per sq foot is the load of the upstairs floor but im just paranoid.

Seems like quite a weak floor...That means if you stand on one foot, you'll collapse the floor.....Check your source again.
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post #13 of 16 Old 01-30-2007, 03:42 PM
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i agree with the last post, 40 lbs.? how old is the house? if within the last few years it should have i joists, (these are what was mentioned to use instead of 2x mat.)but either way find out witch way the floor joists run under your riser and build your riser to cross them.and a little FYI, a 2x10 14' will hold 800lbs in the center(yes it will bow, but not break). good luck
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post #14 of 16 Old 01-30-2007, 05:41 PM
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I would just get I joists like these at your local lumber yard:


If you glue and screw the joists to the sub floor and original floor joists you will end up with a stronger floor.

Human perception is not a direct consequence of reality, but rather an act of imagination. - Michael Faraday
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post #15 of 16 Old 01-30-2007, 06:40 PM
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I just framed my riser similar to how you would a room, only I used 2x6s and framed 12" OC. The lower riser is 14" high and the rear riser is 28" high.


There are no stupid questions, but there are a LOT of inquisitive idiots. Me being one of them at times.

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post #16 of 16 Old 01-30-2007, 07:00 PM
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40 or 50 pounds per square foot (psf) live-load is typical for residential construction. But, that's a MINIMUM, not the point at which the structure fails since that rating has a large safety margin already built in. What that means is that exceeding the 40 psf rating will result in more deflection, not a failure of the system. Failure would likely take several times the rated live-load.

Think of how much a waterbed weighs... With a couple people in a king-size waterbed with the frame and headboard, etc., you're probably putting almost 2000 pounds in less than 80 sqft - or around 25 psf. In fact, you could put EIGHT people in that same waterbed and not exceed the 40psf live-load on the floor. There's an image for you!

Bottom line is that unless you build your riser out of 1/4" plate steel or from a solid block of MDF, you'll be well within typical (and safe) limits - even with 6 people all bouncing in their chairs.

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