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Old 05-17-2018, 02:01 AM   #41
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Originally Posted by N'om'ad View Post
Not exactly - XPS foam is a good choice for a water-exposed situation as it is virtually unaffected by it.






Not exactly either - I've seen a lot of damaged OSB. Ply? not so much. It delaminates if exposed to weather - constant wet/dry cycles = not what it experiences in a bus - and it won't delaminate if it's got weight on it, nor will it expand and push up much like OSB does. One soaking with OSB and it's tear out time
Now I'm confused again. I went through this before I made my choice and was dead set on ply. My neighbor convinced me to go osb because it's more stable, doesn't expand and contract near as much, doesn't warp in a twisting fashion. So I changed my mind. I am concerned about the one soking thing. That scares me.

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Old 05-17-2018, 02:19 AM   #42
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Originally Posted by N'om'ad View Post
Not exactly - XPS foam is a good choice for a water-exposed situation as it is virtually unaffected by it.






Not exactly either - I've seen a lot of damaged OSB. Ply? not so much. It delaminates if exposed to weather - constant wet/dry cycles = not what it experiences in a bus - and it won't delaminate if it's got weight on it, nor will it expand and push up much like OSB does. One soaking with OSB and it's tear out time
You sir are correct. At liest I only have 3 sheets down. I guess tomorrow it comes up. Thank you for catching that for me.

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Old 05-17-2018, 03:13 AM   #43
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Ha ha, fair enough, if you're leaving windows in then the floor will be freezing in winter anyway!

I don't know what your neighbour does for a living but he/she doesn't sound like a carpenter or a builder. I think he/she might, as many people do, be confusing the two. Did you read the link I attached?

Ply is very stable - it's been the traditional backing for tiles for years precisely because it doesn't move much. Wood expands across grain but virtually nothing along the grain. Ply is made of alternate layers at 90 to each other so each layer restrains the other from expanding. A bit of warp disappears as soon as you lay it and to claim that OSB doesn't warp is ridiculous.

Sorry to have freaked you out. Some have argued that if you get a serious water leak you should pull the floor regardless. I'm not sure I agree - I think it would depend on your floor construction (how much 'buried' wood you have) and how quickly and thoroughly you could dry it out.
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Old 05-17-2018, 03:19 AM   #44
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Ha ha, fair enough, if you're leaving windows in then the floor will be freezing in winter anyway!

I don't know what your neighbour does for a living but he/she doesn't sound like a carpenter or a builder. I think he/she might, as many people do, be confusing the two. Did you read the link I attached?

Ply is very stable - it's been the traditional backing for tiles for years precisely because it doesn't move much. Wood expands across grain but virtually nothing along the grain. Ply is made of alternate layers at 90 to each other so each layer restrains the other from expanding. A bit of warp disappears as soon as you lay it and to claim that OSB doesn't warp is ridiculous.

Sorry to have freaked you out. Some have argued that if you get a serious water leak you should pull the floor regardless. I'm not sure I agree - I think it would depend on your floor construction (how much 'buried' wood you have) and how quickly and thoroughly you could dry it out.
Funny you should ask. He is a cabinet maker, and built his own house, he's pretty sharp in alot of areas, just not where I need it I guess. So yeah taking the osb back tomorrow and getting 3/4 t and g ply, I only cut 3 sheets so 60 bucks lost, not too bad. I'm thinking about removing the runner I put in but it just makes me feel better, so in the air on that.how much heat cold could I lose through that thing?
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Old 05-17-2018, 03:33 AM   #45
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My dad had a flooring business most of my life. I've seen some water damage. No wood product holds up perfectly to water it will naturally wick up water. Osb looks worse when it's been soaked but ply delaminates even screwed down or with weight on it. It will feel spongy and crunch when it's dried.

I don't know how much water people plan on having in their bus, but both are laid on floors and roofs in houses.
If it's that scary a pour on garage floor epoxy will seal it up and stop nearly anything
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Old 05-17-2018, 04:33 AM   #46
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My dad had a flooring business most of my life. I've seen some water damage. No wood product holds up perfectly to water it will naturally wick up water. Osb looks worse when it's been soaked but ply delaminates even screwed down or with weight on it. It will feel spongy and crunch when it's dried.

I don't know how much water people plan on having in their bus, but both are laid on floors and roofs in houses.
If it's that scary a pour on garage floor epoxy will seal it up and stop nearly anything
Not a bad idea. I don't plan on pouring nybwager on my floor, but pipes break, sinks leak, roofs leak, sh$t happens. I do plan on doing something to it. Just don't know what.
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Old 05-17-2018, 07:17 AM   #47
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No wood product holds up perfectly to water it will naturally wick up water. Osb looks worse when it's been soaked but ply delaminates even screwed down or with weight on it. It will feel spongy and crunch when it's dried.

I don't know how much water people plan on having in their bus, but both are laid on floors and roofs in houses.
If it's that scary a pour on garage floor epoxy will seal it up and stop nearly anything

I'm surprised to hear this - like I said, I've seen a lot of sheets of ply that have been left out in the rain for a long time and show no signs of damage, can't say the same for OSB. Perhaps it depends on actually being immersed in water and for how long.

A big difference is the amount of compression used in manufacture - I suspect there is much less used with ply as the plies are cut to the exact thickness required so all that is required is to squeeze the glue. OSB on the other hand is made of a layer of loose 'chips' that are squeezed tightly to create a uniform thickness. Water absorption and expansion releases that compression and nothing will get it back.

Just because it's done doesn't mean it's good or best practice - OSB on a floor is a cheap solution that is probably fine for a floor that will likely never see water but I wouldn't ever recommend using it in a kitchen or a bathroom.

Pouring on something on top won't get a coat on the underside though eh? You could do this but it'll cost you, it'll be messy and stinky and ply will do - 5/8" is more than enough btw and T&G would be favourite
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Old 05-17-2018, 08:05 AM   #48
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Marine grade ply. The glue is waterproof.
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Old 05-17-2018, 08:30 AM   #49
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I don't know what your neighbour does for a living but he/she doesn't sound like a carpenter or a builder. I think he/she might, as many people do, be confusing the two.
Maybe he meant MDF and not OSB. MDF is going to be as flat as flat gets. And it will pretty much stay that way... until it gets wet so . It would be great for furniture (cabinets) that will NEVER see water but wouldn't trust it for a bus floor just because of condensation sake much less spills or burst pipes.

Estelle,
You should get him to clarify just for peace of mind.
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Old 05-17-2018, 08:48 AM   #50
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Marine grade ply. The glue is waterproof.
Heavy as hell, more expensive than hell, and kinda stinks. It's probably way overkill too. And probably the route I'll go. I don't mind a little over designed here and there. I'm not building 100,000 units like Jayco.
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Old 05-17-2018, 08:59 AM   #51
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I get the heavy & expensive....but havn't noticed any unusual smell. (Course, my sniffer has probably been affected by years of acid etching.)
I went the marine route for my floor as well as most cabinetry.

One advantage of a Shorty?...

It doesn't take much of anything to fill it up.
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Old 05-17-2018, 09:50 AM   #52
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Plywood versus Osb

Probably the BEST would be marine grade Ply but imho the best overall subfloor material would be advantech osb T&G subfloor material I have seen snow sit on it, melt drip through the seams multiple times dry out and look like new except for the coloration change its all in the glue its made with and that stuff seems to be equal to marine ply but not as pricey.
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Old 05-17-2018, 10:51 AM   #53
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I'm surprised to hear this - like I said, I've seen a lot of sheets of ply that have been left out in the rain for a long time and show no signs of damage, can't say the same for OSB. Perhaps it depends on actually being immersed in water and for how long.

A big difference is the amount of compression used in manufacture - I suspect there is much less used with ply as the plies are cut to the exact thickness required so all that is required is to squeeze the glue. OSB on the other hand is made of a layer of loose 'chips' that are squeezed tightly to create a uniform thickness. Water absorption and expansion releases that compression and nothing will get it back.

Just because it's done doesn't mean it's good or best practice - OSB on a floor is a cheap solution that is probably fine for a floor that will likely never see water but I wouldn't ever recommend using it in a kitchen or a bathroom.

Pouring on something on top won't get a coat on the underside though eh? You could do this but it'll cost you, it'll be messy and stinky and ply will do - 5/8" is more than enough btw and T&G would be favourite
I was thinking of maybe giving it some sort of treatment on all sides before I put it down, but here's a question. The three sheets of osb I have down are in the very back, bedroom, would it be stupid to leave two of those sheets in place and do from there up with ply instead? So to clarify, osb in the bedroom, ply everywhere else? Or is it not worth the 60 dollar savings?
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Old 05-17-2018, 11:18 AM   #54
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I get the heavy & expensive....but havn't noticed any unusual smell. (Course, my sniffer has probably been affected by years of acid etching.)
My sniffer certainly isn't the best in the world. Can you smell the difference between untreated and pressure treated? The marine is just stronger than the pressure. Not strong enough for me to worry about but the gf is hippy dippy and likes to worry about the evils of such things.

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I went the marine route for my floor as well as most cabinetry.
Really? The stuff generally doesn't like finishes either or at least the few times I've messed with it. What are you finishing the cabinets with?
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Old 05-17-2018, 02:21 PM   #55
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Should the floor have 2X2's to prevent the insulation from being compressed? Afterall they say compressing insulation actually makes it less effective.

Or should you just lay insulation with glue then tongue and groove plywood?

Another reason I've heard to use 2X2's is to prevent the floor from warping/sagging under weight differential on each side of your build.


Opinions GO!

We are doing 2" rigid XPS with no frame except for the edge at the front of the bus. Problem:. When you cut the insulation to the width of the bus it does not want to bend enough to get it under the chair rail. My son is in the bus *right now* trying to figure out what to do. I suggested cutting it in half and staggering the joints so he could put one half (about) under the chair rail and set it down and then puttje other half under the chair rail on the other side and set it down in the middle. Is there an easier/better way than that? He broke one trying to bend it.
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Old 05-17-2018, 02:47 PM   #56
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Probably the BEST would be marine grade Ply but imho the best overall subfloor material would be advantech osb T&G subfloor material I have seen snow sit on it, melt drip through the seams multiple times dry out and look like new except for the coloration change its all in the glue its made with and that stuff seems to be equal to marine ply but not as pricey.
+1000

A friend here who is a builder keeps a half sheet of Advantech anchored with a rope and weighted down with a cinderblock in his pond to show how well it holds up.

We've been looking at it for over 10 years now and it still shows no signs of swelling or delamination.

Advantech Plywood, Advantech Sheathing, High Performance Wall Sheathing & Roof Sheathing Panel | Huber Engineered Woods

It is definitely a step up from OSB and personally I think it is a better flooring than plywood.
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Old 05-17-2018, 02:51 PM   #57
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We are doing 2" rigid XPS with no frame except for the edge at the front of the bus. Problem:. When you cut the insulation to the width of the bus it does not want to bend enough to get it under the chair rail. My son is in the bus *right now* trying to figure out what to do. I suggested cutting it in half and staggering the joints so he could put one half (about) under the chair rail and set it down and then puttje other half under the chair rail on the other side and set it down in the middle. Is there an easier/better way than that? He broke one trying to bend it.
Personally I'd be removing the chair rail and side panels on the inside of any conversion. If you don't then what you are losing in thermal bridging on the sidewalls will far offset any gains you get from using 2" XPS on the floor. You may as well use thinner foam that you can bend if you are going that route IMHO.
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Old 05-17-2018, 02:56 PM   #58
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Ha ha, fair enough, if you're leaving windows in then the floor will be freezing in winter anyway!

I don't know what your neighbour does for a living but he/she doesn't sound like a carpenter or a builder. I think he/she might, as many people do, be confusing the two. Did you read the link I attached?

Ply is very stable - it's been the traditional backing for tiles for years precisely because it doesn't move much. Wood expands across grain but virtually nothing along the grain. Ply is made of alternate layers at 90 to each other so each layer restrains the other from expanding. A bit of warp disappears as soon as you lay it and to claim that OSB doesn't warp is ridiculous.

Sorry to have freaked you out. Some have argued that if you get a serious water leak you should pull the floor regardless. I'm not sure I agree - I think it would depend on your floor construction (how much 'buried' wood you have) and how quickly and thoroughly you could dry it out.
Took your advice and others, took out the osb and returned the 6 sheets remaining and purchased 9 sheets of t and g ply. Thanks so much for the advice
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Old 05-17-2018, 03:01 PM   #59
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Personally I'd be removing the chair rail and side panels on the inside of any conversion. If you don't then what you are losing in thermal bridging on the sidewalls will far offset any gains you get from using 2" XPS on the floor. You may as well use thinner foam that you can bend if you are going that route IMHO.
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Old 05-17-2018, 04:39 PM   #60
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Nice use of numbers but here's a question for the non-framers, how do you calculate slope?

With rigid board you're pretty safe but I'm going to use spray foam so will use the 2x2s to keep things level.
Spray foam UNDER the bus......

How could you sacrifice the headroom??

My bus is spray foamed completely from underneath. Loosing 0 of headroom. Used full 3/4 subfloor t&g ply.

I see people doing all this mastic/foam board foam floor craziness but Ive learned that millinials are completely programmed to you tube. Monkey see monkey do. Lets all grow beards together!!
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