This is probably a little like asking “How long is a rope?”
I don’t plan to occupy the cabin roof, but I can see where it might occasionally be handy, or maybe nice for lounging if we chose.
Area is 7’x6’. What “joist” spacing and surface thickness would I need? I know the requirements for a house, but that would be significantly overbuilt for a boat in my estimation.
Will be glassed outside and can be inside if needed.
Jbo
Deck scantlings/loading.
- Jaysen
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Re: Deck scantlings/loading.
This is going to be an odd comparison but might give you an idea.
I built a v12. Hull is 1/4" and has 12oz glass. The largest bottom span is a section about 28" long and 24" wide (I'll measure and update this size once the rain lets up). I can plop my 210lbs on that section and you can't "feel" it flex. It does flex a little you just can't feel it.
That is my way of saying that my experience is that a 24x28" section of 1/4" meranti gassed with 12oz on the outside of the arch can support a 210lb fat guy.
I would think 18" spans made of 3/8" ribs would give you a large margin for safety.
I built a v12. Hull is 1/4" and has 12oz glass. The largest bottom span is a section about 28" long and 24" wide (I'll measure and update this size once the rain lets up). I can plop my 210lbs on that section and you can't "feel" it flex. It does flex a little you just can't feel it.
That is my way of saying that my experience is that a 24x28" section of 1/4" meranti gassed with 12oz on the outside of the arch can support a 210lb fat guy.
I would think 18" spans made of 3/8" ribs would give you a large margin for safety.
Re: Deck scantlings/loading.
Guess I left out an important detail. Max “joist” span will be 6’ due to overhang.
And to make sure I’m clear - NOT a party deck in the least. Literally just to hop up and lay back or maybe if necessary to reach something for some reason(and don’t know what that might be). Would rather plan and not need it than punch through it one day in a pinch.
Jbo
And to make sure I’m clear - NOT a party deck in the least. Literally just to hop up and lay back or maybe if necessary to reach something for some reason(and don’t know what that might be). Would rather plan and not need it than punch through it one day in a pinch.
Jbo
Re: Deck scantlings/loading.
Thanks, Jaysen.
That’s a good reference point.
I was thinking maybe 18” would be sufficient, but wasn’t sure that would be enough with 1/4” skin. I’d prefer to keep the skin at 1/4” even if it meant more joists.
Jbo
That’s a good reference point.
I was thinking maybe 18” would be sufficient, but wasn’t sure that would be enough with 1/4” skin. I’d prefer to keep the skin at 1/4” even if it meant more joists.
Jbo
- Jaysen
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Re: Deck scantlings/loading.
I honestly think you can go wider. Hopefully Jacques or Ried (he's really up on the materials) can provide a more official response.
My 1/4" feel solid with me on it. I'm not jumping on it mind you, but it doesn't need the water to feel strong.
My 1/4" feel solid with me on it. I'm not jumping on it mind you, but it doesn't need the water to feel strong.
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Re: Deck scantlings/loading.
Point loading is the biggie. So, if you need the roof for maintenance; you can go on it and be super careful, if you send a couple gals up there and they start dancing; the loading becomes dynamic and worse than a point load.
I setup my roof to be able to handle snow loads. And it might be too heavy now..but I did.
My rooftop spans 8' by about 12'. The span changes everything. My beams are 1.5" deep and 2.5" wide and elliptical and on 11" centers.
For a 6' span; you can reduce the center spacing. An arch supports more than a flat. But an arch is hard to sun on.
Once you determine if the roof is arched or elliptical, you can determine better the beams. Perhaps you will jist slant it forward so rain heads forward and tanning is less uncomfortable.
I'd say for a lightweight plywood roof, glass skin on back of 12oz and beams on 16-20" centers. Most of this type of thing is self design. So you glass a piece of plywood and then put some beams up on 2x4s and then walk on it to decide. But probably on the order of 1.5"x1.5" would be close... for 7' of them maybe 4-5 beams or so by my gut
I did not glass my plywood skins on the bottom of my roof and punched a hole in one with my knee before the glasswork on top was done, for example. And I was being careful. So glass helps a lot..
I setup my roof to be able to handle snow loads. And it might be too heavy now..but I did.
My rooftop spans 8' by about 12'. The span changes everything. My beams are 1.5" deep and 2.5" wide and elliptical and on 11" centers.
For a 6' span; you can reduce the center spacing. An arch supports more than a flat. But an arch is hard to sun on.
Once you determine if the roof is arched or elliptical, you can determine better the beams. Perhaps you will jist slant it forward so rain heads forward and tanning is less uncomfortable.
I'd say for a lightweight plywood roof, glass skin on back of 12oz and beams on 16-20" centers. Most of this type of thing is self design. So you glass a piece of plywood and then put some beams up on 2x4s and then walk on it to decide. But probably on the order of 1.5"x1.5" would be close... for 7' of them maybe 4-5 beams or so by my gut
I did not glass my plywood skins on the bottom of my roof and punched a hole in one with my knee before the glasswork on top was done, for example. And I was being careful. So glass helps a lot..
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Re: Deck scantlings/loading.
My ceiling is beams with 4mm ply above with 12mm foam core above that with 17oz glass above that. I think glassing the ply panels would have allowed me to use a wider span, but the panels had two seams...so I did not.
Re: Deck scantlings/loading.
This will have some curvature. Undetermined at this point how much. That choice will be based on aesthetics(as much as my caveman brain allows). If it is too much for comfortable lounging and we end up using it much, I will make pads that compensate for the curvature to use when wanted.
Jbo
Jbo
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Re: Deck scantlings/loading.
The way to make beams for curvature is to laminate them with thickened epoxy or sawcut them from hardwood if they are gonna show from below.
Re: Deck scantlings/loading.
Is your answer below you? Spacing that supports your deck?
Also, covering your beams in FG may stiffen them up a bit. What about FG's cousin Carbon Fiber tape?
Also, covering your beams in FG may stiffen them up a bit. What about FG's cousin Carbon Fiber tape?
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