subfloor for dummies

[mudmuffin]

We are not new at Airstream, but are very new at tearing one apart

Got a '91 29' and have decided to tear out the lovely MAUVE carpet and put in laminate. We did that in our home-no big deal...

HOWEVER, we now see that we have some subfloor problems up front and under the beds in back.

We've removed the totally composted particle-board subfloor in those areas and can see that the black frame things (what are those called anyway?) are sort of rusted on top.

All the leaks are now fixed so things should be dry from now on.

Questions:
Do we have to remove the rust or paint those things?

There are some small holes in the thin metal under-skin (What's is that thing called?)
Are those holes supposed to be there or should we seal them?

I understand that exterior (untreated) plywood or marine grade plywood is recommended...yes?

Do we need to treat or seal the raw edges of the plywood? ... if so, what?

I know there are loads of experts out there. help!

and what on eartth is an 'outrigger'.

Where do I learn this language?

[overlander63]

Originally Posted by mudmuffin

We are not new at Airstream, but are very new at tearing one apart

Got a '91 29' and have decided to tear out the lovely MAUVE carpet and put in laminate. We did that in our home-no big deal...

HOWEVER, we now see that we have some subfloor problems up front and under the beds in back.

We've removed the totally composted particle-board subfloor in those areas and can see that the black frame things (what are those called anyway?) are sort of rusted on top.

All the leaks are now fixed so things should be dry from now on.

Questions:
Do we have to remove the rust or paint those things?

There are some small holes in the thin metal under-skin (What's is that thing called?)
Are those holes supposed to be there or should we seal them?

I understand that exterior (untreated) plywood or marine grade plywood is recommended...yes?

Do we need to treat or seal the raw edges of the plywood? ... if so, what?

I know there are loads of experts out there. help!

and what on eartth is an 'outrigger'.

Where do I learn this language?

Hi. The "outrigger" is the metal thingy that goes out from the frame to the sides of the coach, under the floor. Originally they are painted, and if you can access them, it is a good idea to repaint them. You can use a wire brush to get the scaley rust off the metal, and use Ospho or Por-25 to treat the metal, and help keep more rust from forming. When that is dry, you can put a coat of paint over them, and move on to the next problem.
The thin under-skin, if it is what I think you are talking about, is the bananna wrap. It is the curved piece between the lower rub rail and the belly pan. The belly pan is the flat aluminum sheet on the very bottom of the coach.
Treated or Marine grade plywodd is best for floor repairs, for obvious reasons.

[1959newbie]

Mudmuffin,

I am certainly no expert, but I have done some extensive research on Airstream restoration in the past few months -- of necessity, unfortunately!

HOWEVER, we now see that we have some subfloor problems up front
and under the beds in back.

The first thing I'd advise is getting an ice-pick and checking the edges of the floor next to the walls in every area you can get to, under beds, inside cabinets and storage compartments, everywhere you can reach. There may be rotted areas you haven't found yet, I'm sad to say.

We've removed the totally composted particle-board subfloor in those
areas and can see that the black frame things (what are those called
anyway?) are sort of rusted on top.

Good lord, were they really using particle board sub-floors in the 90's??? I knew they used it in cabinetry, but I thought sub-floors were always plywood. Perhaps this was a poor repair by a PO?

All the leaks are now fixed so things should be dry from now on.

Good, extremely important!

Questions:
Do we have to remove the rust or paint those things?

The steel main frame-rails, cross-rails, "stringers" and "outriggers" will all rust away eventually if you don't remove the surface rust and re-seal them. Current "best" product is supposed to be POR-15, but many people use other rust-inhibiting coatings.

There are some small holes in the thin metal under-skin (What's is that
thing called?)
Are those holes supposed to be there or should we seal them?

I assume you are talking about the aluminum "belly skin" which covers the underside of the trailer? There should be insulation between the subfloor and belly skin, is there? A few small holes shouldn't be a problem, unless they are in a place where water can splash up easily and get insulation and subfloor wet -- this area under the trailer is supposed to "breathe," not to be sealed up totally, in order to allow moisture to escape.

I understand that exterior (untreated) plywood or marine grade plywood is
recommended...yes?

Do we need to treat or seal the raw edges of the plywood? ... if so, what?

YES, and YES! As to what, there are many opinions. I am chemically-sensitive and planning to live in this trailer full-time for a year, so I sealed the plywood surfaces and edges with Safecoat's "Water Shield."

and what on eartth is an 'outrigger'.

Where do I learn this language?

"Outriggers" are the pieces of the frame that stick out sideways from the main frame rails (running front to back), extending to the edges of subfloor down both sides of trailer.

Read, read, read on these forums related to what you want to know. Ask questions. Go to theVAP.com and listen to their podcasts on relevant topics. Do enough research so that you can tell the difference between people who know what they're talking about, and people who think they know what they're talking about....

Replacing even part of the subfloor (if problem extends to edge) requires removing all the furnishings in that area and loosening/removing lower inner skins, to gain access to channel where subfloor, frame and shell are all connected.

Good luck!

[mudmuffin]

Overlander63,

Thanks a bunch. My husband and I have torn into this thing and (as usual) bit off more than we were prepared for.

Since you are so kind to answer my first questions, would you mind a couple more?

We have cut out all the crumbly subfloor back to the good stuff and will have to replace about the back four feet , under both twin beds-side to side. We are trying to clean all the crumbs out of that groove that the original floor was wedged into (that has a name, too, I'm sure).

From what I'm reading, it's important for structural stability that the new subfloor fit back into those grooves. Is that right?

If so, how can you do it?

Would bolting the subfloor to the outriggers be enough strength?

What about those holes in the belly pan? Are they or ventilation?

Do we have to seal the cut edges of the plywood with something?

I appreciate your answers so much.

We just sold a 1970 Overlander which we LOVED...in a lot of ways it was better than this 91 that we have now.

MM

[mudmuffin]

Lynne

The first thing I'd advise is getting an ice-pick and checking the edges of the floor next to the walls in every area you can get to, under beds, inside cabinets and storage compartments, everywhere you can reach. There may be rotted areas you haven't found yet, I'm sad to say.


Yes, we have done that and it we have to replace about 67", I was just reminded (not 4 feet as I said before).


Actually, I called it particle board, but it was that chip-board stuff, you know it has big chunks of wood all pressed together. It's definitely NOT plywood and it is original-runs the entire length of the trailer, 5/8" thick.


We've taken out both beds and nightstand and are contemplating how to get a piece of plywood to fit back into that channel.

There are areas in those channels with remnants of the rotten subfloor and are VERY hard to pry out in places. How important is it that the new subfloor fit completely back into those channels like the original?

There are brads that held the subfloor in that channel. We have no way to replace any type of brad without taking the skin off.

Do we just screw the new subfloor to the frame/outriggers?

Thanks

Mary Lynn & Charles

[1959newbie]

Mary Lynn & Charles,

I'm not certain exactly what the detail is in your much-newer-than-mine trailer (perhaps someone has a picture s/he can post?), but the concept in all Airstreams is the same, I believe: the strength of the structure results from strong connections between exterior shell, sub-floor and frame. And where all these things join together is at the very edge of the sub-floor.

So yes, it really IS important to get all the rotten wood out (OSB, it sounds like, is what you had?). And you will have to remove the lower inside panels (as well as anything attached to them) in order to replace a piece of subfloor properly. You will also have to open up the belly pan (unless you try the TEK fasteners "stephrbts" used for her repair), because you'll need a nut on the end of each bolt.

There is an aluminum channel along the edge of the subfloor between the inner and outer walls. Bolts must be fastened through this channel, then the subfloor, then the outriggers. The channel must also be attached to the subfloor, with either screws or more bolts, every few inches in between the outriggers. And the subfloor must also be bolted every few inches to the rest of the frame.

Depending exactly where your patch is needed, this can be not too bad or a huge amount of work. You want the new piece to fit in tightly and to be attached securely to frame and channel.

[mudmuffin]

Thanks to evryone who has responded to our post. The saga continues.

The floor is OSB and labeled as 5/8. I thought that the numbers referred to the thickness of the floor material. Wrong! The thickness is closer to 3/4 inch. We were able to remove all of the rotten wood from the channels and 6 long bolts which penetrated the OSB and channels. They had a nut screwed so tightly the bolt caused a bending, cracking and narrowing of the channel space. The odd thing was the length of the bolts (much longer than needed for the job) and the bolts were all bent above the nut making them impossible to remove by backing off the nut. The bolt had to be cut in the channel, (with a Dremel cut off wheel) the head dropped out and the shaft and nut removed from above. There are three of these bolts on both sides of the trailer in the curved portion of the channels only. They served only to lock the OSB in the channels. None are present along the straight length of the floor to the bathroom wall (approximately 50 inches). These are not the bolts which enter the main center beam or the outriggers. Over these beams the channel is narrowed to 1/2 or less due another bolt whose upper portion at least three inches in length and is bent at 90 degrees. The new flooring will have to be trimmed around these bolts and narrowed to fit the reduced thickness of the channel.

Trying to remove the inside skin to allow access to the upper portion of the channels was complicated as removal of all visible screws and rivets did not loosen the skin section. There are an entire series of rivets beneath the overlying peice of skin (ie not visible until the overlying skin is removed or pulled out from the wall). What this means is that to remove, for instance, the curb side curved piece of skin requires removal of other skin sections on that wall and the end of the coach. Also you have to remove the curtain supports and padded/upholstered bumper pads, each held in place with multiple screws. At least on my 1991 model this is true and a bad design. Working behind the curved skin by pulling the skin out enough to reach back there is made difficult by resistance of the curvature of the skin section.

I will be trying to cut and install the new flooring (3/4 exterior grade plywood treated with Thompson Water Seal) this weekend. Wish me luck!

[Holzarbeiter]

If I'm reading this correct, you are dealing with rot in the rear bedroom. From what you have stated sofar, I get that the area in question is both sides of the curved section towards the rear wall. I'm used to working on an older model but assuming that the design is still the same, I would recommend the ' camshell ' repair method. This entails removing the lower interior panels (I belive you have done this already) removing the rubrail on the outside, droping the belly pan, removing the bananna wrap and the bumper, in that area. Now you have access to the area top and bottom. On my unit, the last sheet of subfloor (decking) is a full 4' to the nearest seem. It made the removal of damaged and installation of new material easy. The installation of all fastners could be done correctly. Any frame issues can be adressed and the frame painted (I recommend POR 15).
I don't know what the original thickness of the OSB was, but be aware that this material will swell when wet.
As far as the bolts bent, that is done from the factory to ensure no Loosening of any fastners.

Hope that helps, do lots of searches, read until your eyes are crossed, asked question as needed. Photos would help as well, so everyone can see what you are trying to deal with.

Good luck, been there, done that.

[1959newbie]

I agree, pictures of what you are talking about re. channel and bolts would help.

But basically, any fasteners coming thru sections of channel surrounding or adjacent to section of subfloor you are replacing MUST BE REMOVED (and yes, it IS tedious and time-consuming, requiring lots of grinding!). The new subfloor must extend under the channel almost to outer skin all the way around, with bolts thru channel and subfloor going into frame wherever possible, and bolts or screws attaching channel to subfloor in between those.

This is a critical component of the strength of the "semi-monocoque" design of Airstreams -- cutting out around the old bolts, leaving the new subfloor not attached at these points, would weaken the overall structure.

The fact that there are no bolts in the rear sounds very strange. Are there holes drilled in the channel? Is there a rear crossmember under the channel and subfloor?

Is the rest of your subfloor OSB, or is this area one that has been a problem before, and a PO replaced rotted plywood with OSB? If there is more OSB, I would sure put a LOT of sealer on it!

Good luck this weekend.

[mudmuffin]

A little more information and a new discovery.

While working last evening on the floor I measured the thinkness of wood that the channel would accept in the rear of the trailer. The channel is narrowed from 3/4 inch to just over 3/8 inch in those areas and from each side starting in the curve, accross the rear to the other curved wall section. This would make insertion of the 3/4 floor impossible in those sites. I went to the front of the trailer behind the couch and examined the end of the flooring accross the entire width of the trailer. I found that the orginal wood factory installed floor had its leading edge routered down to fit into the more narrow channel. After the floor reached the straight sides then this narrowed edge returned to the 3/4 diminsion and entered the channels unmodified from that point on. I am going to follow that design when I begin the installation in the rear of the trailer. Wish I had a digital camers to show each of you but surely other trailers of the area are the same. I truly appreciate the comments and advice you have each provided and it is great to be part of the Airstream family.

[mudmuffin]

Thanks for the assistance. We used many of your suggestions and got the new floor installed. Now I will start with the laminate in the next few days. I look foward to cooler weather and a return to our camping adventures. See you guys on the road!

[Holzarbeiter]

Glad to hear you got it done, post some pic's if you can

[1959newbie]

Kudos for getting it done, and so quickly!