Sub-floor fastening

[gs1949]

Well, thanks for all the information guys. I'm almost convinced, but I will always be concerned about hidden defects in the plywood. I've just seen too many panels get laid up with holes in interior plys so I have trouble believing anything other than that hidden defects are an industry wide problem. The companies of course do try to limit this, but they also constantly push for increased production, so it's an ongoing struggle.

And in my experience T&G subflooring is not a special product. The plywood mill that I worked at the longest made a lot of 5/8 T&G, but there wasn't anything special about the way they made it. They just picked the best panels out of the regular production after they were cut to size and graded, the ones with nice faces and solid edges with no holes showing. Inside these panels would have been the same as all the regular panels with the possibility of holes up to 3 or 4 inches in interior plys. And I don't think the quality of the product this place turned out was at all unusual in any respect. Plywood is made very quickly and people can and do miss things they should ideally deal with.

I've been reading customer reviews of 5/8 T&G subflooring on a Home Depot page. The most common complaint was problems with getting the tongue to go into the groove, but there was one review that dealt with my main concern about any plywood, no matter what grade it is: "I understood that sub flooring was supposed to have more integrity than regular plywood. What I mean is that there should not be any empty spaces in plys themselves. When we cut the floor we found many empty spaces in multiple levels of the plys."

Finally, I must admit that I was not planning on using glue, just lots of screws. Glue is probably a good idea even with furring strips, but obviously essential without the strips to screw into.

So what kind of glue are people using?

[farok]

How about AdvanTech? This product comes up from time to time, and looks like OSB, but it doesn't absorb or hold moisture, which tends to plague OSB, and has a lifetime warrantee (not that I'm thinking of using the warrantee in a bus, which they would probably baulk at). Since it's not ply-based, it wouldn't have "holes" in it either. The few times it is talked about, it seems like a good option. Any thoughts from the pros on this thread? It comes in 3/4 T&G, and I was looking at it for my bus.

Chris

[o1marc]

gs1929 with your experience with holes in ply while manufacturing, can you name one instance in the real world where it was an issue in use? I was in the construction business, never ever heard of an issue like you describe. I have seen poor quality layers depending on the grade you buy. But even those did their jobs to spec.
You sound like an engineer with no real world application experience.

[gs1949]

@Farok, I've never heard of AdvanTech before. It looks interesting, but the webpage I found calls it sheathing, not subflooring. That distinction makes a huge difference in plywood, but I'm not sure how much of a difference there would be with this synthetic stuff. I will keep reading about this stuff, thatnks for pointing it out to me.

@Mark, it's gs1949, not 1929. I'm not that old yet. I'm guessing that your construction experience probably did not include cutting much plywood, because otherwise I'm pretty sure you would have had some experiences like the HomeDepot customer I quoted above. I've had plenty of experiences like that over the years.

But if I am wrong and you did cut up quite a bit of plywood and never found any coregaps, split centers or other hidden internal defects, then I would like to know where the plywood came from because their quality control is obviously superior.

And maybe you're right about me being like an engineer without a lot of real world experience. When I was a kid I was constantly taking things apart to figure out how they worked and to see if I could make them better. Usually at first I was lucky if I got them back together, but I kept trying and got better at it, so that turned out to be a habbit I have never completely gotten over. I'm still trying to make things as tough as I can make them.

[edit] @ Farok, I did find a page on subflooring. That stuff sounds very interesting, but of course they don't say how much it costs. I'll have to find a retailer for that.

And to my surprise, AdvanTech has a dealer about 20 miles from me, so I will go have a look at that stuff the next time I am over that way.

Thanks very much for pointing AdvanTech out to me. Unless it is outrageously expensive, I think I will use AdvanTech.

[o1marc]

Originally Posted by gs1949

@Farok, I've never heard of AdvanTech before. It looks interesting, but the webpage I found calls it sheathing, not subflooring. That distinction makes a huge difference in plywood, but I'm not sure how much of a difference there would be with this synthetic stuff. I will keep reading about this stuff, thatnks for pointing it out to me.

@Mark, it's gs1949, not 1929. I'm not that old yet. I'm guessing that your construction experience probably did not include cutting much plywood, because otherwise I'm pretty sure you would have had some experiences like the HomeDepot customer I quoted above. I've had plenty of experiences like that over the years.

.

AdvanTech was all I used for flooring in the homes I built. I checked the other day and Home Depot no longer carries it.
gs1929, I'll assume by this comment that you intentionally misspelled my name


Huber Engineered Wood | AdvanTech Flooring Panels | Huber Engineered Woods

[gs1949]

No it wasn't intentional, Mark is my brother's name, and so I spelled it that way just out of habit. I don't think that is as bad as intentionally adding 20 years onto my age, so I am not apologizing, just explaining.

[o1marc]

Originally Posted by gs1949

No it wasn't intentional, Mark is my brother's name, and so I spelled it that way just out of habit. I don't think that is as bad as intentionally adding 20 years onto my age, so I am not apologizing, just explaining.

It was not intentional, didn't know it was your birthday.

[Tango]

I make my own T&G flooring. A router and biscuits will keep any ply flat & perfectly smooth across the seams. Piece-O-Cake. Even with marine ply.

[alpine44]

Advantech 23/32 flooring is about $35 for a 4'x8' sheet. Regular OSB in same thickness about $20. Advantech is a whole lot heavier, more rigid, and resists water much longer than OSB.

The manufacturer of Advantech, Huber Engineered Woods, also offers ZIP panels which is exterior sheeting with a water resistant, vapor permeable membrane laminated on a base panel of similar density and rigidity than Advantech. You may have seen these panels on houses before the siding went up. Typically green for wall sheeting and brown (thicker) for roofing. The seams between the panels are either taped with the waterproof ZIP seam tape or caulked with their special sealant.

My box van does not have a sheet metal floor like most skoolies and the pine floor planks were screwed directly onto the steel floor joists, exposed to road spray on the underside. After 15 years, that floor was rotted out in several places.

As a replacement, I plan to use the ZIP panels with the laminated barrier towards the road, cut so that the necessary seams will be on the steel floor joists. Before laying down the panels, I will put sill tape on top of the steel joists and coat their topside with the ZIP caulk. This will seal the seams of the panels and prevent the membrane from being chafed through on the joists. The panels will be screwed to the steel joists.

A base layer of XPS foam followed by another XPS layer with PEX radiant heat tubes and aluminum heat transfer plates in it will go on top of the ZIP panels.

This will then be topped with Advantech sheets and covered with the same vinyl plank flooring that Lowes has in their appliance departments. That flooring is very abuse resistant and looks great IMO.

One thing I still have to figure out is how to best construct the removable floor panel that allows access to the Lithium house battery located underfloor between the frame rails.

[Sleddgracer]

Originally Posted by farok

How about AdvanTech? This product comes up from time to time, and looks like OSB, but it doesn't absorb or hold moisture, which tends to plague OSB, and has a lifetime warrantee (not that I'm thinking of using the warrantee in a bus, which they would probably baulk at). Since it's not ply-based, it wouldn't have "holes" in it either. The few times it is talked about, it seems like a good option. Any thoughts from the pros on this thread? It comes in 3/4 T&G, and I was looking at it for my bus.

Chris

I would seriously check what glues are used in making AdvanTech - some of the manufactured wood products are extremely flammable because of the glues used in their manufacture - in a mobile home for instance, you literally only have a couple of minutes to get out if there is a fire - fire is something that concerns me in a closed place like a skoolie - closed cell foam gives off a poisonous gas once it's heated to a certain point and especially dangerous if it's not covered, and if OSB is used with all it's glue - - -- well, I don't even want to think about it

[plfking]

Originally Posted by gs1949

I don't completely trust the plywood, any plywood, because I know that all plywood is not created equally. I spent somewhere around 8 or 9 years all together working in 4 different plywood mills spread around Oregon and British Columbia. So I am very aware of the shortcuts people take and what they get away with.

There can be big holes in core or in centers, and the people laying up the plywood just break a chunk off a piece of scrap, either with glue or without glue depending on what's missing and put it in the hole as quickly as possible while paying basically no attention to how well it fills the hole. There just isn't time for that.

If the holes in one ply are even a little too big there will be an area nearly the size of the hole where the other plys will not be stuck together really firmly, and they will often come apart or delaminate while the plywood is cooling in a stack before it gets cut into finished size and graded.

Delaminations can also result from either too much glue or too little glue. And there are a number of other things that can weaken plywood All those small defects are pretty much undetectable when the panel is new. A few small holes in inside plys don't matter much unless you're building a boat, but enough small weak spots can add up to seriously impact the strength of the plywood.

All good points, and absolutely true. Used to be a manufacturing engineer for one of the Steelcase subsidiaries, and we were one of the first to implement plywood tab construction for interior frames in institutional furnishings. We learned during the R&D phase that even high-dollar plywoods would delaminate fairly rapidly when subjected to the 100,000 cycle BIFMA testing.....so much so that we had to use Russian birch plywood for our frames. Material cost was significantly higher, but yield was significantly better, and it easily passed every single BIFMA test we threw at it.

[musigenesis]

I don't like the idea of screwing the furring strips into the floor since that means poking a bunch of holes in the floor. I'm planning a subfloor with 3" high joists (they're not really furring strips at that point) and on part of the floor I'm going to attach them to the sheet metal floor by screwing L-clips to them at the bottom and then spot-welding these to the metal floor (long weird story but I'm doing that to support the metal floor by attaching it to the subfloor).

Personally I think the free-floating subfloor would work fine, and if you wanted to attach it rigidly to the metal floor, adhesives would work fine too. But if you wanted furring strips and you wanted them more firmly attached then with adhesives, I'd go the screwed + welded L-clips route in preference to putting holes in the floor with screws.

[Yukon Cornelius]

Originally Posted by musigenesis

I don't like the idea of screwing the furring strips into the floor since that means poking a bunch of holes in the floor. I'm planning a subfloor with 3" high joists (they're not really furring strips at that point) and on part of the floor I'm going to attach them to the sheet metal floor by screwing L-clips to them at the bottom and then spot-welding these to the metal floor (long weird story but I'm doing that to support the metal floor by attaching it to the subfloor).

Personally I think the free-floating subfloor would work fine, and if you wanted to attach it rigidly to the metal floor, adhesives would work fine too. But if you wanted furring strips and you wanted them more firmly attached then with adhesives, I'd go the screwed + welded L-clips route in preference to putting holes in the floor with screws.

Out of curiosity...how tall are you? The interior height of your rig? And what's your intended sub ply thickness and finish flooring? Going to be a warm floor with 3" joists and insulation, but at a serious cost to the headroom.

Not trying to poke holes (see what I did there ) I just like to understand where people are coming from and what their intended goal is.

[mrpincher]

In Amarillo our Lowes stores carry the Avantech line. I used it as a sub-floor in my 1940 pier and beam house becuase it was very rigid and uniform in thickness. I didn't use it for its water resistant claims.



After I installed it in my bus, I threw a cut-off piece out in the snow/waterpuddle to see how it would hold up in the freeze thaw cycle here in Amarillo. Left it there for a month and put the calipers to see how much it changed. There was less than a 1/64 inch difference between the pieces in my shop and the piece outside on the ground. The surface texture was different. The piece outside was mildly fuzzy to the touch. A peice of 220 grit would have peeled that off in seconds.


Just my test - my way - not science. Try it for yourself.

[farok]

Thanks - real interesting test, and it shows that it remains pretty consistent. Did the piece you left out seem to have any sort of mold or other nasty growth on it after it being so wet?

The Lowes here carries it as well. As for fire rating, the flame spread rating is the same Class III as plywood. It weighs about 20lbs more per sheet, so there's a difference, but not terribly significant (about 80lbs for my bus). I think it may come down to how uniform the fir T&G plywood also available looks. Both are comparable in price (and I can't seem to find marine ply).

Chris

[mrpincher]

I didn't notice any mold colored stains. The piece was muddy on one end.



The instructions on mating the T & G states that you should leave a gap (can't remember how much). I tend to over drive the panels in an attempt to close the gap - after I get tired of beating on them, I remember the gap will not close and pull them back apart and set them properly. I wish the gap would close. I'll tape over the gap before I place the final flooring.



I used 2" ridgidfoam under the sub floor and used angle brackets to attach the sub-floor to the outer walls of the bus. My interior walls are firmly attached ot the roof of the bus and the sub-floor. With luck it will all stay in place.

[gs1949]

@Farok, there is a company here in Western Oregon, Roseburg Lumber Co., that still makes Douglas Fir marine grade plywood. I have no idea what they charge for it, but it will be quite expensive, and probably difficult to find.

In addition to using different glue, they will use a higher grade of core and centers, and lay it up much more slowly and carefully, so as to have no hidden holes or gaps inside the panel.

IMO using marine plywood for subflooring in a bus would be serious overkill. I was somewhat surprised to find a local dealer of Advantech out here on the Coast, so I intend to use that, and will probably buy some next payday.

And another point about plywood, although I am not sure how much this applies to subflooring I think plywood should have an odd number of plys. Five ply 5/8 panels should be easy to find, but 3/4 and 1/2 inch will most often be 6 or 4 ply.

Having an even number of plys involves putting 2 glue covered pieces next to each other, and so the amount of glue applied to the contact surface must reduced to avoid delamination. And of course if the glue is reduced too much delamination will result. This is just one more thing that can go wrong. Personally I would never buy 4 or 6 ply for anything, even building a doghouse.

[farok]

Thanks for the insights!

[Sleddgracer]

Originally Posted by gs1949

@Farok, there is a company here in Western Oregon, Roseburg Lumber Co., that still makes Douglas Fir marine grade plywood. I have no idea what they charge for it, but it will be quite expensive, and probably difficult to find.

In addition to using different glue, they will use a higher grade of core and centers, and lay it up much more slowly and carefully, so as to have no hidden holes or gaps inside the panel.

IMO using marine plywood for subflooring in a bus would be serious overkill. I was somewhat surprised to find a local dealer of Advantech out here on the Coast, so I intend to use that, and will probably buy some next payday.

And another point about plywood, although I am not sure how much this applies to subflooring I think plywood should have an odd number of plys. Five ply 5/8 panels should be easy to find, but 3/4 and 1/2 inch will most often be 6 or 4 ply.

Having an even number of plys involves putting 2 glue covered pieces next to each other, and so the amount of glue applied to the contact surface must reduced to avoid delamination. And of course if the glue is reduced too much delamination will result. This is just one more thing that can go wrong. Personally I would never buy 4 or 6 ply for anything, even building a doghouse.

I don't know if things have changed or not, but the last time I bought 1/2" sheathing in the US, it wasn't made with waterproof glue - in Canada, even the cheapest plywood is made with water proof glue - I have a sleddog kennel, board dogs, and do behavior therapy for dogs with problem behaviors - at a guess, I'd say we have about 60 dog houses that are made from 1/2" sheathing - they last for years out in the weather as long as they have legs to keep them off the ground and I keep a coat of paint on them - they are more likely to wear out than they are to come apart

[gs1949]

I think most 1/2 sheathing made in Canada after the mid-70s is four ply. I was working in Prince George then and we started making a lot of of 4 and 6 ply around 1976 or 77. I'm convinced that the 5 and 7 ply that got replaced were stronger, and less likely to delaminate.

And I also think you are 100% correct about Canadian glue being more water resistant.