floor construction (not to heavy (i hope))

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floor construction (not to heavy (i hope))

Postby del » Fri Oct 20, 2006 12:22 pm

now is time for a question (my first go easy). i am in the process of building the floor. i would like to use 3/8 plywood with one by (3/4 in reality) framing plus innsulation. my ? is do i need to put a bottom under (1/8 inch ply?) the whole mess to be strong enough? i am building it to sleep on ,not dance or walk.

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ps will have pictures when i figure out how to make them small enough. they have to many pixles, but do not know how much to many.
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Re: floor construction (not to heavy (i hope))

Postby halfdome, Danny » Fri Oct 20, 2006 12:43 pm

del wrote:now is time for a question (my first go easy). i am in the process of building the floor. i would like to use 3/8 plywood with one by (3/4 in reality) framing plus innsulation. my ? is do i need to put a bottom under (1/8 inch ply?) the whole mess to be strong enough? i am building it to sleep on ,not dance or walk.

thank you
del
javascript:emoticon(':thinking:')
Thinking


ps will have pictures when i figure out how to make them small enough. they have to many pixles, but do not know how much to many.


Del, Welcome. What grade of 3/8" plywood are you thinkg of? I went with 1/2" Baltic Birch and I feel it's strong enough. I added 1/8" Baltic Birch ply to the underside to seal up the foam insulation but it isn't necessary as most will agree. Look under notices to learn how to resize and post pictures. Have fun with your build, :) Danny
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Postby Miriam C. » Fri Oct 20, 2006 12:49 pm

I set my pictures to a width of 500 to 600 that way you won't have typing all over the page. The clicky up above "help with photos" will help.

Now the floor. 3/8 should be thick enough you aren't going to get that roudy in something that short. :lol:

When I came here 1x3 framing and 1/2 on top and 1/4 (maybe 1/8) luan on bottom was the advice. Insulaton is great and if you use the pretty pink or blue stuff it is firm too.

The bottom is merely a pan to keep water and dirt out. Some don't use it. I would. JMHO

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Postby sdtripper2 » Fri Oct 20, 2006 1:32 pm

Help with pictures and sizing can be done here as well.

Click here > Layout of the Forum, Avatar & Tools /Newbies, Start Here
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Postby Ira » Fri Oct 20, 2006 2:05 pm

Del, a lot of us Cubby builders, per plans, used small 2 by 2 framing (actual 1 1/2) and 3/4 ply for the floor.

If you go 3/8 ply, you'll need more frame members. A minimal amount are needed for 3/4 ply.

And most people DON'T put any ply on the underside.
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Postby jmtk » Fri Oct 20, 2006 2:35 pm

Del,

That's exactly how I did mine: 3/8" for the top layer, 3/4" framing with pink insulation inside, and 1/8" for the bottom layer. The plywood was all Baltic birch. All the surfaces are securely glued together with polyurethane construction adhesive. I have crossmembers on my 5x8 trailer chassis about every 2 feet for support of the floor, and 1x2 crossmembers in the floor to match. It's quite rigid. While building, I routinely stand in the galley area to access the roof, and I've never felt any flexing. When I decided on these floor specs, I was aiming for something more lightweight than the typical 3/4" ply that most people use. We also camp throughout the year, so wanted insulation in the floor.

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Postby Arne » Fri Oct 20, 2006 4:19 pm

This is good information. I had thought about a sandwich floor, so it would be flat on the bottom and more aero.... takes a bit more up front thinking, but I like it.
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Postby del » Fri Oct 20, 2006 5:15 pm

thank you everyone. i do believe i will put the ply on the bottom.

the pictures will take time (i am not good with computers, as the help pages are confusing to me)

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Postby Ira » Fri Oct 20, 2006 7:14 pm

Okay guys--I may just play an asshole on TV, but there's more to this than meets the eye.

(Is anyone old enough here to remember THAT reference?)

When you put ply on the underside, you're creating an environment to collect water within that floor frame. And I didn't just make this up--it's well-documented by much lesser assholes than me.

There are things that guys and gals did or may have done here to minimize this problem, but this can create a very real problem just the same.

The point is, as long as the underside of your floor is well protected with roofing emulsion or other, similar material, you just don't need that extra piece of ply there. And it will add NOTHING structurally.

Okay--lesser assholes may now chime in.
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Postby jay » Fri Oct 20, 2006 8:18 pm

birch is not weather resistant; it's meant to be used for interior architechtural woodwork & casework.
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Postby dwgriff1 » Fri Oct 20, 2006 8:41 pm

You are building barges.

Mine is sandwich construction without a frame. 1/8 skin underneath, 1" of foam insulation (ribs 12" oc) and 2 layers of 1/8 on the floor, going in opposiste directions.

Even that is probably overkill.

My 22' coachmen has a thin interspring mattress on prescious few really ugly 3/4 by 1 1/2's and a layer of 1/8" lauan between the mattress and those ugly sticks.

I gulped when I saw it, but it's done well for 20 years.

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Postby WoodSmith » Fri Oct 20, 2006 8:53 pm

Ira wrote:When you put ply on the underside, you're creating an environment to collect water within that floor frame. And I didn't just make this up--it's well-documented by much lesser assholes than me.

Okay--lesser assholes may now chime in.


I don't know if I qualify as a lesser or greater asshole - but I have never understood this. Why is the floor of the tear any different from the wall or ceiling? Most any tear with insulation has ply on both sides of the insulation on both the walls and the ceiling/roof. What is it that causes a construction method that no one worries about when used on walls and roof/ceilings to create an instant water tank of rot when used in the floor? :thinking:

What is the source of the water?

Road spray? How can that be worse than a heavy rain on the roof or walls - both of which likely have holes in them for windows, vent fans, lights, water fill ports...

Condensation? From what I have read, most of the condensation that people report is on the roof and walls, the floor usually has a thick foam or air mattress covering most of it providing isolation.

Moisture coming up from wet grass? How can this be worse than rain or a heavy dew?

If the complaint is weight or that it is simply unnecessary that's fine, but how is it a water issue? Please help me understand :?

Why are there no reports of insulated sandwich walls rotting away at the bottom where all the water would collect?

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Postby asianflava » Fri Oct 20, 2006 8:57 pm

My sandwich floor is 1/8" birch outside 3/4" foam and 1/8" birch inside. I glued it together with thickened epoxy. I was able to stand on it with 9ft between supports (I ain't no lightweight)

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Postby Arne » Fri Oct 20, 2006 9:36 pm

I would be concerned about puncturing 1/8" on the top of the floor... could be you are onto something though, maybe 1/4" on top, 1/8" on the bottom...

re water. If there are no holes there is no water..... the bottom of my trailer rarely gets any water from road spray, and asphalt emulsion would keep that out. I would not be concerned about water.
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Postby halfdome, Danny » Fri Oct 20, 2006 10:24 pm

I tend to agree with Woodsmith, he has a valid point and he doesn't seem like an a-hole. I have 1/8" Baltic Birch Gorilla glued with asphalt emulsion and have been in downpours at freeway speeds. The underside is cleaner than the top side after a good rain. It hardly gets wet but then I have 15"' wheels. :) Danny
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