Originally Posted by JaycoJake06
So here are some pics of the trailer before I tore it apart. Also a pic of yesterday's work putting the deck on. The leading plywood is not attached yet as I need to decide on a few details on final termination. It's 1/4" birch, flexes well, looks like it's blemished in the pic but that's just some weird color spots like knots or something. The rest is 3/8 BCX sanded one side. I'll need to shim the 1/4" to match the 3/8" at the rafter.
I'll have a fair bit of filling and sanding to the deck plywood before applying the membrane. I'm thinking plastic wood? Not sure what would be the best filler. I used subfloor glue and staples as fasteners, was too concerned about splitting thin rafters with screws. The factory used screws and there was damage.
A few comments,
I am not sure what roof material or glue you are using. I use the Dicor 901BA
This water based glue needs a porous substrate to bond to. As such, the glue will not bond to plastic wood. So I do not use filler per say, I have other methods to deal with gaps etc.
What areas are you filling? If you are doing the plywood seam joints, I use fiberglass mesh drywall tape. I called Dicor and talked with them on it as their instructions state to use their fleece backed tape on the seams if the gap is over 1/16" and I cannot find it for sale anywhere. They said they changed that and the old instructions are not updated. They said to use the mesh tap as it will span the joint gap, and the glue will go through it to create a much better bond. The new glue does not bond to the fleece tape which is part of why they do not use it anymore. The older oil based glues may have bonded to it.
And yes , run the sander over all the joints and high spots. I use a 3" x 21" belt sander.
Another area to talk about, the 4 x 8 sheets wrapped over an arched roof 8 ft. wide, the plywood falls short about 3/8 to 1/2" split even on both sides in the flat at the side wall to roof transition. That creates a 3/8" tall bump and hollow area the roof membrane needs to go over the top of. I have created 2 ways on how to deal with that bump/hollow area. For sure, sand a radius on the top of the sheet to not cut the membrane.
First method was to use Dicor non sag caulk tooled out and fill the voided transition it and build it up. That does work well but it can take 3 coats to build it up enough. And it takes time for the Dicor to cure. A week or more can go by building it up that way, but it does work.
The next method which I now use all the time, is to build up that area with commercial grade butyl tape. It sticks to the wood and the membrane. You can do the roof membrane the same day you put the butyl down. I started tucking a 1" x 1/8" wide strip of butyl in that joint and it works, but the 1" is too wide and too thin and you have to keep rolling the membrane to flatten it out. The next revision was to get 3/16" thick x 3/8" butyl which fits right in that void nicely. This one https://www.bestmaterials.com/detail.aspx?ID=16289
Also, what membrane are you using, EPDM, TPO or PVC?
A heads up on the glue, lets talk about the glue and getting the right rate applied. Unless you have done this a few times, you never put enough glue on the first time and an area too big. That fresh plywood will suck up that glue big time if you are using the wet method of applying the membrane. You have to put enough glue on to transfer to the membrane and it be well coated. If you want to go over this, just ask, I'll explain more.
On the topic a staples on the decking, there can be issues with staples. In your case you put construction adhesive between the deck and the rafter and then stapled, that might elevate the issue, not sure.
I do screw all my decks and intentionally. But, I do it the long way. I use a depth gage set stop type of countersink with a short pilot drill. This creates a clean cut hole at the surface and a starter pilot in the rafter. There is no bulging or bunching up of the wood at the surface. The starter hole in the rafter takes care of rafter wood splitting. I use a cordless drill with a clutch setting to set the screw torque. The goal is a dead flush screw to a very slight depression (1/64" to no more then 1/32"). Not a big depression, as then poke marks show up on the membrane where there is no support and the glue does not stick to metal. A sharp edge putty knife test over the top will tell you if the head is slightly up, then hand tighten down. This takes longer to do, but creates a better job in my view. Then sand over all of that in case a screw corner is up.
The staple issue I have found, under towing road vibration and twisting, staples can back out. I have seen them do this on siding and roof membranes and that's bad news.
I have a project camper I acquired that had a new PVC roof installed by a local shop to the prior owner. They stapled the deck on, in this case, 1/4" luan plywood. They did several things not right on that roof job which are not a long lasting install. They cracked the membrane with the awning brackets creating two holes in the roof in sort order after the new roof was on. This allowed water to get into the wall. Three years went by and the wall and floor was gone, that and the window flange leaks. They also never caulked the top joint of gutter rail to the membrane. Some manufactures don't, but that is a risk for a leak, sooner or later
I also see the staples lifting in the center of the roof. This is not a little, it is approx. 1/8" to 3/16" in some spots. Those lift areas have non popped through yet, but in time they can. I have this camper apart enough to dry it out. When rebuild time comes, I will have to tear off the entire roof and start over.
Since you glued the decking to the rafters, the sheet movement and the staples will be greatly reduced. It may not even show up, but keep an eye on it. The glue will do most all the anti twist and movement prevention of the plywood I would think, not allowing the flexing plywood to start pulling up the staples.
You mentioned, you had damage from the Jayco screws, what damage did you find? Did you unscrew the screws to lift the old decking or just lift the sheet pulling the screws out? Always good to learn on these things.
Hope this helps.