Plywood for '73 Safari

[SafariGeorge]

Greetings - Has anyone used birch plywood instead of spruce for floor replacement? I am wondering if the added cost ($60 CAD per sheet vs. $32 in my case) brings any longevity benefits. I suspect added weight is a negative.

Thanks in advance
George

[kevin242]

I think your best choice for floor replacement would be marine-grade plywood, especially in areas that have the potential to get wet again in the future. Marine-grade is treated to prevent rot & decay unlike regular plywood.

Kevin

[kennethowens]

I was thinking "treated" plywood also.

[wasagachris]

I agree with Kevin. Marine grade is the way to go. It's a bit pricey though. I used it on my floor and it was $126 CAD a sheet. You would need 5 sheets for a 23'. The is a thread about the condition of plywood these days. The poster shows pics of cutoffs left out in the rain and it had curled up and all the plys had seperated. I left my cutoffs outside in the rain and they didn't change one bit. No curling or seperation. A couple of days after the rain and the wood looked just the same after it had dried. You should coat the sheets both top and bottom with something to stop water penetration. I used a paint used to make aquariums and my floor is totally impervious to water.

[Wabbiteer]

I was disappointed in marine grade plywood - the eight layers were nearly perfect without voids but overall the majority of them had the consistency of balsa wood. My '73 27' uses heavy self-tapping Phillips screws with a machine thread and trying to get a consistent clamping torque even inches apart was almost impossible - some bores needed countersinking and some bores the screw dived way below the surface of the wood with almost no force.

If I were to do it again I would canvas lumberyard and look in their catalogs with the manager and get a strong near-structural grade plywood, I believe there is a scaffold grade plywood that has all the water-proof resins and consistent gnarly tough ply materials.

As wasagochris said coating the floor is a good thing, he mentioned top and bottom sides but our trailers use the outside edges for as shell tie-down clamping - thin your choice of coatings down a LOT and let it penetrate the edge laminate areas until it mostly rejects wicking additional paint in. its a pain to keep flooding the areas but it will better protect the plywood as the wood itself weakens from dry-rot over the next eleventeen years.

I used Vinyl Ester resin and did two thinned coats just into the edges and then three coats over all - one hitch to using vinyl ester resin is it is extremely hard so dropping a hammer or the like on it, or crushing down bolts shatters the coating, there is little stretch to it, but everywhere else is armored very well...

[DanB]

So this got me thinking, what is the goal in floor replacement/repair?

Of course we want durability, integrity, and long lasting. So the original plywood only lasted 37 years. Hmm.

I'm not saying replacing the plywood with the expensive stuff is a bad thing, but I just got to wonder about the "Return on Investment"?

Plus, I'd really have to think about those chemicals used to protect the wood. Is outgassing a problem with treated lumber in the interior of a "closed" environment? I have the same question about the resins suggested.

If (when) I have to do a airstream floor, I really think I'll grab some normal plywood and maybe do something to protect the edges.

Heck, got to leave something for the next owner to fix, right?!

[r carl]

Originally Posted by kennethowens

I was thinking "treated" plywood also.

Dont confuse green treated plywood with marine grade plywood.

[Wabbiteer]

Everything loosens and droops with age, eh? Gravity is not so friendly after scores of years, and corruption of bright new shiny objects is inevitable as order is dispersed into chaos.

I think given our older trailers construction have once experienced flying down the road in 'loose' formation I want the part I stand, eat and sleep over which happens to hold the other assemblies square with the world to be the strongest a few exrta dollars can make them.

[Chuck]

you definitely don't want "pressure treated" in an indoor space, due to off-gassing.

I'm not a wood or woodworking expert, but it was my understanding that "marine grade" plywood is not "treated" in any way, and is no more water proof than any other untreated plywood. It just doesn't have any voids.

Many people use marine epoxy to treat the outer perimeter and edges of whatever type of plywood they choose, as this is the area most likely to be exposed to water.

[Dave Park]

Pressure treated wood is a huge no-no, because it contains copper and chromium, which are two metals that LOVE to corrode other metals around them. Only specially treated/coated metals/fixings should be allowed to contact pressure-treated wood.

[till]

I have just gone through this.....
3/4" BC exterior grade plywood is what was there. If you keep the leaks at bay and take care of your trailer all will be fine. Like you said, the first floor lasted X years.... take care of it and the new floor will last X years +.

I'll get off the soap box now.....

[Dave Park]

Also, note the quality and stability of plywood has improved in the last 40 years - more stable resins and better materials preparation at the plant gives us a more conformal and durable product - if kept dry.

The more expensive products provide a small specification increase for a large increase of price.

[Wabbiteer]

Everyone keeps talking about the process glues being better these days when now the competition for select wood grains in the international market has gone through the roof --- any sheet of plywood bought 'inexpensively' at a big box store does NOT have the same wood fiber qualities as might've been found in the 60's and 70's, you can't compare or probably replace the plywood Airstream specified and awarded contracts for year-to-year from back then, the forestry stocks simply no longer exist to be harvested!

[r carl]

Originally Posted by till

Like you said, the first floor lasted X years.... take care of it and the new floor will last X years +.

Plywood nowday's is not what it used to be.

[Dave Park]

I don't think anyone's suggesting that you buy the cheapest plywood from a home improvement store However, they can order much better materials at very competitive prices.

[CapnTom]

I used a 3/4" A/C fir plywood for my floor replacement. I was questioning the supplier about marine grade plywood and explained my application. They suggested the A/C Fir. They said it uses the same marine grade resin in the a/c fir as the the marine grade plywood. The difference being the A/C center cords are made with wood chips as opposed to the marine grade where they use solid wood veneers.

After cutting and fitting my pieces I painted the tops with poly, and the edges and bottoms with primer before installation. After the install it sat in the rain for a few days before I was able to put the shell back on and it looked great. No water damage or swelling what so ever. The water beaded up on the poly and the edges were clean and dry. I'd use the same material again. The unit is near completion and and the floor looks great. I used a commercial sheet vinyl floor covering. I have pictures posted so you can check out my progress and floor and such if you like.

[SafariGeorge]

Thanks for your input and opinions- did not answer the hardwood question, but reflects what you and others have stated here before. The floor is after all the last thing to scrimp on and even expensive product is relatively cheap in total, especially 5 sheets for the Safari.
George