Screwing into my subfloor after I just filled holes?

[lanegordon]

So, I have finished ripping out my seats, and am in the process of cleaning up the floor and going to be moving forward to the subfloor in a few days. The question is: After cleaning up and sealing all the holes from the old seats... am I really about to put more holes in this dude by attaching the firing strips? Is there a particular approach I should take (place to screw) or do I just deal with the fact the the underside is going to have "water entry" points with the new screws I put in or do I just deal with it. I'm assuming that stainless steel screw are the way to go for the sake of them not rusting, but is there any "industry standard" idea for not recreating the same problem when I attach the strips?

[FlyboyHPD]

If you're going to spend any length of time in it and be in cold weather it really would behoove you to completely take out all the old flooring. That way you'll be able to see if there is any major rust on the steel floor that needs to be removed/repaired. And also will allow you to put down new poly-iso foam insulation first, and then a new plywood floor on top of that.

You don't need to put down any furring strips at all. Just create a semi-floating floor with the new insulation and plywood. If you put down 1/2 in plywood then only buy screws long enough to go into the total thickness of the plywood and no further. That way you won't be putting holes into the steel floor.

[lanegordon]

Thanks for your reply.

The old floor is all out and and stripped down to the bare metal (and I have some rust repair to do for sure) 😁

I'm confused about not using furring strips. How would I attach the new play wood floor down if I'm not screwing into strips? Also, fastening down walls/ etc would be important for safety reasons wouldn't they?

[FlyboyHPD]

Congrats on getting all the old flooring out and taking care of any rust. Plus it usually winds up smelling better without the old rubber floor and rotten plywood.

The floating floor concept confuses a lot of people. Make sure the new plywood you buy is at least 1/2 inch or thicker (5/8 or 3/4). And you can actually save some money by going with OSB plywood if you plan to place some type of laminate flooring on top of it.

Anyway, no strips are needed because once you screw framing lumber into the floor for any walls you are putting up those framing members will also be attached to the ceiling framing members with the studs you use. Then once you attach cabinets to the floor and then also to the side walls the floor really isn't floating anymore and will be securely held down by everything that you attach to it. Make sense?

[jazty]

Yep, don't put screws through if you can avoid it (and I think you can).
I would recommend this sandwich:

1. Metal floor all cleaned up, holes filled and painted.
2. PL Premium glue. PL also makes a glue specifically for rigid foam (PL 300, I think?), but it doesn't stick to steel worth anything. I experimented with PL Premium and found that it didn't eat into the XPS foam and sticks much better.
3. at least 2" of XPS foam. No EPS or polyiso with the foil face. The foil face will do nothing when directly against plywood or steel and it is a poor surface to glue. You want foam that can withstand the compression of human bodies.
4. PL Premium glue
5. 5/8" or thicker plywood.

[lanegordon]

What about a vapor barrier? Also, thoughts on gluing with the adhesive you listed here SOME firring strips that I could at least attach the middle seam on the plywood to? (Assuming I'll have middle seams). That way I can keep the board square from shifting (although I'll obviously try to cut them to fit tight).

[jazty]

The metal floor already is a vapour barrier. Adding another will eventually trap moisture between the metal and the barrier, which will promote rust. That's my thinking, anyhow. Also, the XPS foam is almost a vapour barrier. That's another reason not to use the foil faced stuff: the foil is very much a vapour barrier and moisture can easily get trapped between the floor and foil through capillary action.

If you use tongue and groove plywood you won't have any seams to worry about. If you put a bit more of the Pl Premium in the groove before pulling them together you will end up with one contiguous floor piece.

If I were to do it all over again this is the approach I would take. Currently my floor is metal, foam glued to the floor, T&G plywood glued to the foam then screwed down (no firring strips. very much unnecessary with XPS foam and an unwanted thermal bridge). I wish I would have skipped the screws. The screws probably don't transfer a significant amount of heat (or cold) in or out, but in the winter they do ice up. Then when the bus interior heats up there are little pools of water at the screw heads until it evaporates. The screws just aren't necessary, in my opinion.

[lanegordon]

That makes a TON of sense. THANK YOU! I'm assuming for the fuller sheets that will work great (what direction would you run your sheets of plywood? Also, as I get up around the steps, etc., there I will like have to fasten things down (plywood wise) to a certain extent, yes?
Ooh! One more "secondary" question while I have you: How many of you rip up the flooring in and around the driver's seat? Is that typically a place of a lot of "rot" and "mess"? Mine seems solid, but it's old and the rubber flooring is kinda gross.

[WhiteWhale]

Originally Posted by lanegordon

That makes a TON of sense. THANK YOU! I'm assuming for the fuller sheets that will work great (what direction would you run your sheets of plywood? Also, as I get up around the steps, etc., there I will like have to fasten things down (plywood wise) to a certain extent, yes?
Ooh! One more "secondary" question while I have you: How many of you rip up the flooring in and around the driver's seat? Is that typically a place of a lot of "rot" and "mess"? Mine seems solid, but it's old and the rubber flooring is kinda gross.

I did not rip up the small square of plywood/rubber located directly under the drivers seat. On my Am Tran this section was separate from everything else and elevated about an inch taller, with different steel flooring for the seat to bolt down to. I opted not to mess with the structural seat anchoring, especially when I found that one of the bolts would not come out as the welded nut in the floor was spinning freely.

As for the floating floor concept, I am glad I stumbled upon this thread. I am getting very close to laying down insulation and subfloor and had been planning to anchor furring strips to the metal floor with screws. After reading this I may reconsider. But not having the floor, or subsequently the cabinets etc, anchored to the floor in a moving bus concerns me. Our proposed layout and relatively open concept so there are very few walls to help anchor the floor to the ceiling. I suppose the cabinets along each side could serve to attache the floor to the walls. But I still feel like a hard slam on the brakes would put a lot of stress on those few attachment points from the whole floor shifting forward. And of course in a worst case scenario, I would think a rollover would be disastrous....

Also, is only certain foam board capable of handling the direct load with no furring strips? I haven't noticed such ratings on the products at my local home improvement stores. Is there concern of compaction over time?

Thanks

[FlyboyHPD]

Originally Posted by WhiteWhale

It would put a lot of stress on those few attachment points from the whole floor shifting forward. And of course in a worst case scenario, I would think a rollover would be disastrous....

Also, is only certain foam board capable of handling the direct load with no furring strips? I haven't noticed such ratings on the products at my local home improvement stores. Is there concern of compaction over time?

Thanks

What you could do to keep from putting holes in the steel flooring is to attach the furring strips into the side walls. Then screw the plywood into the strips from the top.

As for the foam board insulation I've done plenty of research and polyiso works just fine and since you are putting sheets of plywood over it the load distribution and compression of the foam board is not a factor. There is also no reason to use glue on the insulation or the plywood. As long as you lay it all down wall to wall and screw the plywood down on top of it, it's not going to shift.

[lanegordon]

Originally Posted by FlyboyHPD

What you could do to keep from putting holes in the steel flooring is to attach the furring strips into the side walls. Then screw the plywood into the strips from the top.

Would you toenail the furring strips into the sides? And would you do it where he ribs are?

I like the idea of having SOME parts attached to the body of the bus.

[FlyboyHPD]

Originally Posted by lanegordon

Would you toenail the furring strips into the sides? And would you do it where he ribs are?

I like the idea of having SOME parts attached to the body of the bus.

I don't believe you would need to toenail, I'd just go straight in. Pre-drill holes in the furring strips to keep them from splitting only if you need to, and also pre-drill smaller holes in the rib for the screw to get started. The ribs typically exist every 2.5 ft and are in line with the window ribs. I'd definitely drill into the ribs for the best support and holding power.

[WhiteWhale]

Originally Posted by FlyboyHPD

What you could do to keep from putting holes in the steel flooring is to attach the furring strips into the side walls. Then screw the plywood into the strips from the top.

As for the foam board insulation I've done plenty of research and polyiso works just fine and since you are putting sheets of plywood over it the load distribution and compression of the foam board is not a factor. There is also no reason to use glue on the insulation or the plywood. As long as you lay it all down wall to wall and screw the plywood down on top of it, it's not going to shift.

Thanks for the response. Perhaps you could just clarify a few things though. You say that the foam can handle direct load from the plywood but then you also mentioned using furring strips. So do you recommend using furring strips or no?

Also, you mentioned screwing the plywood down on top of the insulation. Do you mean all the way down through metal floor? Or into furring strips? Or just into the insulation?

Thanks!

[lanegordon]

If you read a bit up in the thread, the recommendation is to NOT drill in the the steel belly. Just into the furring strips and without going into the floor. I'm getting excited to tackle this next step!!

[FlyboyHPD]

Originally Posted by WhiteWhale

Thanks for the response. Perhaps you could just clarify a few things though. You say that the foam can handle direct load from the plywood but then you also mentioned using furring strips. So do you recommend using furring strips or no?

Also, you mentioned screwing the plywood down on top of the insulation. Do you mean all the way down through metal floor? Or into furring strips? Or just into the insulation?

Thanks!

I'm not using furring strips myself because my floor will be secured by all the floor to ceiling walls I'm putting up plus all my floor cabinets attached to the floor and side walls. In your case you may want the furring strips.

Cut the foam insulation to fit inside the furring strips and then cut the plywood to fit just over the top of the furring strips and use screws only long enough to go through the plywood and almost to the bottom of the furring strip. That way the screws will not be going into the steel floor.

[WhiteWhale]

Originally Posted by FlyboyHPD

I'm not using furring strips myself because my floor will be secured by all the floor to ceiling walls I'm putting up plus all my floor cabinets attached to the floor and side walls. In your case you may want the furring strips.

Cut the foam insulation to fit inside the furring strips and then cut the plywood to fit just over the top of the furring strips and use screws only long enough to go through the plywood and almost to the bottom of the furring strip. That way the screws will not be going into the steel floor.

So are the furring strips screwed to the metal floor?

[FlyboyHPD]

Originally Posted by WhiteWhale

So are the furring strips screwed to the metal floor?

No. We're trying to avoid putting holes into the steel floor. Use 2x2's or whatever size you choose and attach the furring strips to the side ribs by putting screws into the sides of the furring strips.

[WhiteWhale]

Originally Posted by FlyboyHPD

No. We're trying to avoid putting holes into the steel floor. Use 2x2's or whatever size you choose and attach the furring strips to the side ribs by putting screws into the sides of the furring strips.

Oh ok, got ya. I am only going with 3/4" insulation and furring strips so screwing to walls could be tricky. Thanks for all the info!

[jazty]

No screws. No furring strips. We are in the age of adhesives. Using an adhesive removes potential squeaks and will hold everything down and in place. PL Premium is cheap insurance if you're worried about not having enough cabinetry or walls to hold the floor in place.

Tongue and groove plywood plus some adhesive creates a single giant piece of plywood. Ship lap XPS with some adhesive creates a giant piece of foam. That's all I have to say about it!

[dan-fox]

Originally Posted by jazty

No screws. No furring strips. We are in the age of adhesives. Using an adhesive removes potential squeaks and will hold everything down and in place. PL Premium is cheap insurance if you're worried about not having enough cabinetry or walls to hold the floor in place.

Tongue and groove plywood plus some adhesive creates a single giant piece of plywood. Ship lap XPS with some adhesive creates a giant piece of foam. That's all I have to say about it!

Can you buy shiplap foam sheets or do you have to get creative?