Horror Story - Floor Replacement - Help

[Joe Z]

Ken - Problem is there's a frame in the way underneath. The only way a 1x6 would work is on top of the floor and that wouldn't make much sense. Maybe what you are referring to is if I had to add a small piece of plywood and hadn't cut the old flooring back to the first frame cross members. My new section of floor will actually have self tapping screws gowing through to the frame on all sides except for the edge under the "U" channel which will be attached with carriage bolts. I've attached a picture of what I'm talking about. My new piece of flooring actually shares the frame with the old flooring.

[Chuck]

check out this photo by "sneakinup":




this is a "factory" job...but for an early '70's trailer. the crossmember on the left is actually shorter in height than the one on the right, by about 5/8ths of an inch. Just enough room for a 5/8ths strip of plywood, glued and screwed as a seam reinforcement. the flooring on these years was laid across the frame, with joints like this every 4 feet. Perhaps this is what Ken is thinking.

[Ken J]

Its always been my understanding that you should not make a seam over a cross member. Can you cut away a little more to make the joint?

Ken

[upallnight]

Originally Posted by Ken J

Its always been my understanding that you should not make a seam over a cross member. Can you cut away a little more to make the joint?

Ken

Ken
All the seams on my coach were on crossmembers, I don't see any other way of doing it and acheiveing the same amount of stability. That's why I welded the strip down the center when I replaced my floor.

[markdoane]

Ken,
Mine were the same as Leonard's. Bolts were about 6" OC, staggered on opposite sides of the joint. Or maybe we misunderstood. did you mean no seams over the frame members?

[upallnight]

Originally Posted by markdoane

Ken,
Mine were the same as Leonard's. Bolts were about 6" OC, staggered on opposite sides of the joint. Or maybe we misunderstood. did you mean no seams over the frame members?

Don
Nice picture, you must have the fastestest camera in Wayzata!

[Ken J]

First off I have to qualify myself in that I'm not an expert. Having said that, all that I've read and heard from some of the A/S tech folks over the years on floor repairs is that you should use the method described above. I realize that A/S has its seams over the cross members soooo, what I conclude is that when it comes to smaller section repairs, and when I reread my A/S manuel last night, it says you should use a piece of 4in wide plywood under the seam. And as I've been following this over the years, I have understood that you should not put a seam over a cross member.

So my conclusion.... is that when doing smaller patch jobs, you should use that joint so that the strength is at least as strong as the original larger piece of plywood.

To me this makes sense with what Andy was saying in poor patch jobs, if you break up (in terms of strength) a larger piece of plywood, then you weaken the structure, however, if you can make the "patch" at least as strong or stronger than what was originally there, thats a good thing.

I think we have to remember, everytime you put a seam in you have added weakness there - the lesser the seams, the stronger the structure.

[Ken J]

I did happen to have breakfast with an engineer this morning and presented the question to him, without any backround, which way is best to lay the plywood.

At first he said the best way was crossways - because side to side strength was most important. He said it depends on how far spaced the cross members are. I told him it was a "box" - cross members being about same length as distance between the frame rails. He said most of the weight of the shell is on the outriggers, so after talking awhile.

Again the above answer was based on my "cold" question - then I started with the "what if questions"

In the end, because of the way the frame is made, does not make a whole lot of difference with way the sheets are put down. He gave me so for every xxx distance there needs to be xxxx distance stuff......

He was the one who mentioned the fact that whereever there is a seam, theres a weakness - in the end he felt that length wise sheets were fine - however - he said he would put a 12" sheet of plywood (glued and screwed) down the middle - doing that would really add strength to the sheets. He said a steel joint down the middle might allow some flex. But again said that weight is on the outside and as long as you have more wood inside then frame then outside it would be fine.

Anyway, thought I would pass on one engineers take on the matter.

Ken

[upallnight]

Ken

That would make since as far as floor covering options go also. If you seam it as suggested there would be very little difference in the level of the surface, making it much easier to cover with vinyl.

[Ken J]

Don

Yeah, I for sure would not have a seam on a frame member. As you go down the road its the frame thats attached to wheels and hitch thats taking the impact, so a seam at that point I don't think would be a good idea.

Ken

[Chuck]

Originally Posted by Ken J

And as I've been following this over the years, I have understood that you should not put a seam over a cross member.

.

and yet, as evidenced in the photo I posted above, this is exactly the way Airstream did it. again, that x-member is 4 3/8 inches tall, while the one on the right is 5". every 4 feet along the frame, the x-member is short like this, to allow a 5/8 reinforcement to join the seams on 2 sheets of plywood...and the joint is directly over a x-member.

I don't know how this could be considered "wrong", or weaker in any stretch of the imagination, unless you're comparing it to an 8' x 24' single sheet of ply...and I don't think they make 'em that big. Think of the way houses are built. joists, 16" on center...all plywood seams *must* be over a joist, on all edges. No building inspector would sign it off otherwise. and if you need to cut a hole for some reason, headers must be installed for the repair, or joists must be "sistered", so that no edge or splice is unsupported....no glued n screwed splices allowed. In the pic above, the "joist" (cross member) supports the splice, which eliminates any weakness, and replaces it with added strength.

[upallnight]

Chuck
I have come to the conclusion that we are talking about three different generations of A/S's. Don's and mine are late 50's early 60's, no added support at the seams, just bolted to the crossmembers. Yours and Ken's are 70's vintage evidently with reinforced seams and Joes is 80's vintage evidently with no seams, single sheet layed over entire frame. This could be the cause for the debate on different joining methods if I'm correct.

[Safari Tim]

Chuck,

I'm just curous since I have a 70's trailer. I understand the crossmember is lower to allow for the overlapping plywood. But on the top, how does that work w/o having an uneven joint?

[Chuck]

doh! I think I see the error of my ways...you're talking about the frame members..the main 5" c-channel that runs the length of the trailer, not the cross members. right?

in that case...yeah. I agree.

nevermind.

however, I think it could depend on exactly where the seam is in relation to any outriggers in the vicinity. I'm sure there's a formula...x thickness of plywood can span y distance with z amount of support on n sides....that sort of thing.

[Chuck]

Originally Posted by Safari Tim

Chuck,

I'm just curous since I have a 70's trailer. I understand the crossmember is lower to allow for the overlapping plywood. But on the top, how does that work w/o having an uneven joint?

a picture is worth a thousand words....(it made me type something )

[Safari Tim]

Ahh....

Thanks!

[Ken J]

Thats it - I would think that would work - to me thats not a seam over a cross member because the 5/8" piece in essence make it one piece.

Ken

[87MH]

Originally Posted by upallnight

Chuck
I have come to the conclusion that we are talking about three different generations of A/S's. ......80's vintage evidently with no seams, single sheet layed over entire frame.

The '87 345 floor is a single piece of OSB - no seams (that I remember).

I had the whole thing exposed when I installed the Pergo flooring last year.

[markdoane]

In the end, I think everyone is going to use the method that makes the most sense to them. After Ken's discussion with the engineer, I'm going to go with a 8" backup splice, glued and screwed. I like that it means I only need to make half as many seams over the crossmembers.
I'm also going to offset the center seam 4" to one side, alternating from one side to the other. That way I can make fewer cuts, and leave the existing center angle in place.
I noticed that this method requires less total length of 'seam' compared to the original. With the center seam added in, the total seam length is 332", compared to 400" using the original method.

[Joe Z]

Finally feel like I'm getting somewhere. Over the last few days I've done the following:
1. Removed the lower beltline so that I could jack up the "U" channel in the rear about a 1/4" and squirt a bead of Vulkem under there. This is the section of the "U" channel that sits right above the rear trailer box. This is where my main "remaining" leak was coming from.
2. Removed banawrap on drivers side rear corner so that I could get at the new floor and install additional carriage bolts without having to notch that section of flooring when sliding it in the "U" channel. Haven't put floor in for good yet though. Still diagnosing and fixing leaks.
3. Removed another section of inner sking under rear drivers side window. Diagnosed leak. Water was coming from two places. Rivet line where skin overlapped and a leaky rivet holding center beltline to trailer. All have had a liberal coating of Vulkem applied. That piece of inner skin has been reattached.
4. While removing the lower beltline had to remove a rather thick bead of caulking that one of the dealerships had applied to it and the rear box before I could jack up the "U" channel. This in turn resulted in having to scrape it and some paint off of the rear box, requiring me to sand, prime and repaint part of my rear tool box. Good thing I had some Airstream metallic grey sitting around.

Joe