Roof replacement help

Mlg567 · 04-19-2019, 01:39 PM

I have a 1995 vectra 33ft. My fiberglass roof is toast. I purchased Epdm to replace it with. After taking a closer look at the roof construction. It looks like the roof is made of a thin sheet of paneling on top of foam. I was expecting plywood. I have no idea what to replace the wood with, or if I should just peel the paneling off and glue epdm to foam. Any advice is greatly appreciated. I have no idea why this super thin wood paneling is up here. How can my roof be sturdy with no plywood

**ThomB** · 04-19-2019, 02:51 PM

I'm not sure I can help much but I was under the understanding that the fiberglass in atop a thin layer of underlayment with the fiberglass tucked into Win's proprietary side wall/ roof joint. There is a 4-part video on youtube showing the replacement of the roof that you may want to search out/ watch. I think that between the underlayment material and the fiberlass you end up with a roof that you can walk on. I'd think you want to replace the fiberglass with fiberglass or go right over top of it with the new material (but not sure how that works).

here is one of them.

https://www.youtube.com/watch?v=TXGfXl4zO38

Mlg567 · 04-19-2019, 03:33 PM

I saw this but it looks like his motorhome has a thick layer of plywood

al1florida · 04-19-2019, 03:54 PM

Your Winnebago fiberglass roof is a very well made and sturdy composite roof structure.

There is a thin sheet of lauan plywood with a layer of fiberglass on top. Beneath this wood/fiberglass is about 3 inches of white Styrofoam with another piece of lauan plywood on the bottom side of the Styrofoam. All three pieces, glued together, this make a lightweight sturdy roof.

Taking the top layer of wood/fiberglass off will significantly weaken the structure.
Additionally as long as the wood is still glued to the Styrofoam, pulling it off will rip off some or quite a bit of the Styrofoam leaving a very uneven surface to glue the rubber to.

A sheet of rubber directly on top of the Styrofoam would quickly dent into the Styrofoam and perhaps loosen the glue binding the rubber to the Styrofoam.

What is wrong with the existing roof that you need to replace it?

I was going to add a picture of the roof structure, but I don't see a way to insert a picture. It looks like I would have to upload the picture somewhere first.

BobC · 04-19-2019, 04:14 PM

I don't know about your vintage MH but later ones are an extremely strong, foam sandwich with a layer of thin, 1/8" plywood laminated onto the top and bottom of two or so inches of foam. The fiberglass panel itself is pretty thin, about .06" thick.

You can see this cross section about 10 min into this video:

https://www.youtube.com/watch?v=BJz7doxPQXg

Since you already have the EDPM, I suggest not disturbing the existing roof and just apply the EPDM over the top of it. If you can give more details about what you mean by "toast" we can possibly make more suggestions about what to do before applying the EDPM.

If you didn't already have the EDPM, a couple of coats of a good, marine topside paint designed for fiberglass boats might be sufficient if it's only the gelcoat that's deteriorated. I'm considering doing this to my 2002 since the fiberglass surface is getting pretty porous.

It's my understanding that a roof replacement like that shown in the video posted by ThomB can cost as much as $10,000. I suspect that a significant part of this is labor since I can't imagine that the materials are super expensive.

Mlg567 · 04-19-2019, 04:20 PM

Quote:

Originally Posted by al1florida

Your Winnebago fiberglass roof is a very well made and sturdy composite roof structure.

There is a thin sheet of lauan plywood with a layer of fiberglass on top. Beneath this wood/fiberglass is about 3 inches of white Styrofoam with another piece of lauan plywood on the bottom side of the Styrofoam. All three pieces, glued together, this make a lightweight sturdy roof.

Taking the top layer of wood/fiberglass off will significantly weaken the structure.
Additionally as long as the wood is still glued to the Styrofoam, pulling it off will rip off some or quite a bit of the Styrofoam leaving a very uneven surface to glue the rubber to.

A sheet of rubber directly on top of the Styrofoam would quickly dent into the Styrofoam and perhaps loosen the glue binding the rubber to the Styrofoam.

What is wrong with the existing roof that you need to replace it?

I was going to add a picture of the roof structure, but I don't see a way to insert a picture. It looks like I would have to upload the picture somewhere first.

Pieces of the fiberglass roof is missing exposing the wood. I bought it like that. I figured it would be better to replace with epmd.

Mlg567 · 04-19-2019, 04:25 PM

Is it possible to just add material on top off wood where fiberglass is missing or cracked

BobC · 04-19-2019, 05:11 PM

So you do have wood under the fiberglass. I thought, from your original post, that you didn't. Can you post some photos for us? The good thing is that cosmetics aren't an issue so repairs don't need to be pretty. It all depends on the extent of the damage.

al1florida · 04-20-2019, 05:17 AM

Quote:

Originally Posted by Mlg567

Pieces of the fiberglass roof is missing exposing the wood. I bought it like that. I figured it would be better to replace with epmd.

Assuming the area fairly small, say no more than about 4' x 5' or maybe a few feet larger, and the wood is still in good condition, I would just buy some fiberglass cloth and a gallon or more of fiberglass resin and just slap that on. It won't look real pretty, but it will give a really strong roof covering. The fiberglass cloth you buy is much, much thicker than what Winnie puts on the original roof.

**ThomB** · 04-20-2019, 06:30 AM

Quote:

Originally Posted by Mlg567

I saw this but it looks like his motorhome has a thick layer of plywood

No, if you watch you can actually see him replace the entire thing including the wood.

al1florida · 04-20-2019, 07:30 AM

Quote:

Originally Posted by Mlg567

Is it possible to just add material on top off wood where fiberglass is missing or cracked

Yes, Get some fiberglass cloth and resin and cover over the wood.

HOWEVER, if part of what is missing is the part which goes over the edge to the side wall, that is different. Watch this video again where he shows how the fiberglass tucks into the sidewall.

https://www.youtube.com/watch?v=TXGfXl4zO38

BobC · 04-20-2019, 09:45 AM

You can buy Filon roofing material which is similar to (or possibly the same as) what Winnebago uses.

Although more expensive than the fiberglass cloth repair, you could replace the damaged sections with Filon and tape the joints with Eternabond tape. It won't be pretty but will be a lot less work and a lot less messy than using fiberglass cloth or mat and resin.

al1florida · 04-20-2019, 11:17 AM

Quote:

Originally Posted by BobC

You can buy Filon roofing material which is similar to (or possibly the same as) what Winnebago uses.

Although more expensive than the fiberglass cloth repair, you could replace the damaged sections with Filon and tape the joints with Eternabond tape. It won't be pretty but will be a lot less work and a lot less messy than using fiberglass cloth or mat and resin.

Looks much better than fiberglass cloth. The filon could even go over the side and fit into the sidewall grove like the original installation did.

thataway4 · 04-24-2019, 04:33 PM

If you decide to replace the fiberglass, which is what I would do--having worked with fiberglass boats most of my life--I would use epoxy resin, to get the best bond. One layer of 6oz cloth laid on faired wood/fiberglass would be plenty. You will have to paint over the fiberglass/epoxy resin to protect the epoxy from UV radiation. The epoxy will have several times the bonding strength of the secondary bond with the polyester resin. If you wish you could repair the areas where just the wood is exposed, fair that in, with the rest of the roof, and then cover with the EPDM (Which I consider to be an inferior roof material)

NeilV · 04-24-2019, 05:13 PM

The 1995 Vectra which is what my previous coach was has the same fiberglass/plywood stress skin panel construction with aluminum ribs cast into it as the current models so whatever repair you do has to restore that structural integrity which replacing the fiberglass and plywood/luan with rubber is not going to do.

It is built more like the hull of a boat and as such needs to be repaired like you would the hull of a boat replacing the missing plywood core bonding it to the foam and laying up fiberglass mat over it and overlapping a taper ground into the remaining fiberglass to make up a homogeneous whole. Finishing it off with gel coat or an epoxy paint is the last critical step. Be careful with adhesives as you do not want to use one that will react badly and melt a hole/void in the foam. You would want to bond in joining strip made out of at least 1/4 inch plywood in under the existing plywood all around the area being patched screwing it to both sides of the joint to better insure it lays even and is securely attached to the existing plywood so your repair will be less likely to zipper open around the edges of the patch.

Winnebago service advisors will be able to advise you as to what adhesives, etc are compatible. You may also be able to order new complete roof panel if the physical damage left unattended for an extended period of time as described has rotted too much of the structure inside the roof assemble.

jbrattain · 04-24-2019, 06:59 PM

The first used motorhome I bought was a Georgie Boy with an EPDM roof. After a year or so the roof needed to be replaced. A local RV repair shop replaced it with aluminum. They formed the curve from the top of the roof to the awning rail with no problem. Total cost for the install on the 27 foot motorhome was about $2500. I had been quoted as much as $35-3900 for EDPM or aluminum. I think that could be easily done to replace the Winnebago fiberglass roof, and that's what I'll have done when my Winnebago roof needs replacing.