Adhesive for Aluminum roof to plywood?

[Aubrey0418]

My husband and I are rebuilding a camper and are about to get to our roof install. We are doing a seamless aluminum roof which will be going over plywood. We want to avoid using any type of screws as much as possible to install this roof.
What type of adhesive would you recommend using for aluminum to plywood? Also it's a 16ft camper so we will have to find a way to apply adequate even pressure throughout while laying the roof down..any suggestions on that?

[Huntindog]

Gdetrailer wrote:

Huntindog wrote:

As far as the OPs question, aluminum roofing does not need glued down, it is secured via screws around the entire perimeter, the middle floats. In fact it needs to float to allow for expansion and contraction with temperature changes

The reason most manufacturers don't use aluminum is the expansion and contraction, especially on large units. Most leaks are not from the material (whatever it is) failing, but from the sealant around various necessary penetrations failing. Aluminum because of the large amount of expansion/contraction is very hard on the sealant.... It can easily fail in the short warranty periods that RVs typically have... That costs money in warranty claims... And that is why the manufacturers have moved away from it. The flexible roofing most use now have a certain amount of "give" that is beneficial to the sealants, and the do not expand/ contract much.

Huntin'.. COST is the factor and reason, not the expansion/contraction.

Price aluminum vs the cost of EPDM/VINYL/TPO and you will quickly realize that you will save hundreds of $$.

RV industry and manufacturing is a COST driven thing, lower the cost and increase profits, RV industry like any other manufacturing industry must make enough profit to make it worthwhile to stay in business.

If one can save $100 in materials and labor per unit and you build say 10,000 of the same item per year, you now have an extra cool 1 MILLION DOLLARS in PROFITS (yeah that is $1,000,000) that now can be pocketed by the CEO and management..

That IS how real businesses work.

They don't care one bit about if it will make it past the measily 1 or 2 yr "warranty" period, they CAN afford to "fix" your broken RV under warranty because they SAVED money UP FRONT when building it.

Re read what I wrote. You are actualy making my point.

I had an older aluminum roofed RV once... The sealant failure around penetrations is real. All of my subsequent RVs have not had aluminum, and not suffered any sealant failures.

I do not know the cost of aluminum vs the others. I do know that the sealant fails at a high rate with aluminum. That costs manufacturers money, in warranty claims and customer disatisfaction. If aluminum is more prone to failure, and the cost is equal, It is a win for the manufacturer9 (and the consumer). If it is more expensive, then it is even more so.
Again: Most leaks are NOT a result of the roofing material failing. But from the sealant failing at penetration areas

[Gdetrailer]

badsix wrote:

NRALIFR wrote:
The aluminum sheet on the roof of my TC isn’t glued to the wood at all. IIRC there is a layer of felt or closed cell foam between the aluminum and the wood, but it’s held down by the perimeter trim and screws. I don’t think I’d try to full-spread glue it.

I would also pass on the EPDM, TPO, or any other flexible membrane roofing. Nothing beats aluminum.

In other words, what he said ^ :B

:):)

yes you will want the felt or some kind of insulation that aluminum is going to sweat not a good situation.
Jay D.

RV and Mobil home manufacturers NEVER put anything under an aluminum roof. Yes, I HAVE worked on mobile homes and I HAVE delt with RVs with aluminum roofs, there is NOTHING THERE, not even plywood.

The aluminum just lays over top the roof ribs..

Not saying it is the best way, just saying that IS what has been done.

You are always free to do what you think is best..

[Gdetrailer]

Huntindog wrote:

As far as the OPs question, aluminum roofing does not need glued down, it is secured via screws around the entire perimeter, the middle floats. In fact it needs to float to allow for expansion and contraction with temperature changes

The reason most manufacturers don't use aluminum is the expansion and contraction, especially on large units. Most leaks are not from the material (whatever it is) failing, but from the sealant around various necessary penetrations failing. Aluminum because of the large amount of expansion/contraction is very hard on the sealant.... It can easily fail in the short warranty periods that RVs typically have... That costs money in warranty claims... And that is why the manufacturers have moved away from it. The flexible roofing most use now have a certain amount of "give" that is beneficial to the sealants, and the do not expand/ contract much.

Huntin'.. COST is the factor and reason, not the expansion/contraction.

Price aluminum vs the cost of EPDM/VINYL/TPO and you will quickly realize that you will save hundreds of $$.

RV industry and manufacturing is a COST driven thing, lower the cost and increase profits, RV industry like any other manufacturing industry must make enough profit to make it worthwhile to stay in business.

If one can save $100 in materials and labor per unit and you build say 10,000 of the same item per year, you now have an extra cool 1 MILLION DOLLARS in PROFITS (yeah that is $1,000,000) that now can be pocketed by the CEO and management..

That IS how real businesses work.

They don't care one bit about if it will make it past the measily 1 or 2 yr "warranty" period, they CAN afford to "fix" your broken RV under warranty because they SAVED money UP FRONT when building it.

[badsix]

NRALIFR wrote:
The aluminum sheet on the roof of my TC isn’t glued to the wood at all. IIRC there is a layer of felt or closed cell foam between the aluminum and the wood, but it’s held down by the perimeter trim and screws. I don’t think I’d try to full-spread glue it.

I would also pass on the EPDM, TPO, or any other flexible membrane roofing. Nothing beats aluminum.

In other words, what he said ^ :B

:):)

yes you will want the felt or some kind of insulation that aluminum is going to sweat not a good situation.
Jay D.

[Huntindog]

As far as the OPs question, aluminum roofing does not need glued down, it is secured via screws around the entire perimeter, the middle floats. In fact it needs to float to allow for expansion and contraction with temperature changes

The reason most manufacturers don't use aluminum is the expansion and contraction, especially on large units. Most leaks are not from the material (whatever it is) failing, but from the sealant around various necessary penetrations failing. Aluminum because of the large amount of expansion/contraction is very hard on the sealant.... It can easily fail in the short warranty periods that RVs typically have... That costs money in warranty claims... And that is why the manufacturers have moved away from it. The flexible roofing most use now have a certain amount of "give" that is beneficial to the sealants, and the do not expand/ contract much.

[PNW_Steve]

Another option :

My Jayco has a one piece galvanized steel roof. It's almost 30 years old and no leaks.

[Lwiddis]

No issue with adhesive, should be used, but screws are also necessary IMO.

[NRALIFR]

The aluminum sheet on the roof of my TC isn’t glued to the wood at all. IIRC there is a layer of felt or closed cell foam between the aluminum and the wood, but it’s held down by the perimeter trim and screws. I don’t think I’d try to full-spread glue it.

I would also pass on the EPDM, TPO, or any other flexible membrane roofing. Nothing beats aluminum.

In other words, what he said ^ :B

:):)

[Gdetrailer]

badsix wrote:
why not use the EPDM rubber roofing material used on most RVs. its probably not much more than aluminum in cost and probably easier to install. use Dicor self leveling sealer for any penetrations and you'll be good to go. I sure wouldn't want an aluminum roof with screws of any kind in it if I was looking for long life. Google RecPro, Dicor EPDM roofing
Jay D.

Because "EPDM" and any other flexible non metallic roof solution is a short lived 10yr-15yr fix.

Aluminum can often go 30yr-50yrs without being replaced which makes aluminum far cheaper but yet far superior overall. RV industry moved to using EPDM, vinyl roofing because it is cheaper than aluminum roofing, requires less skill and less labor to install which = MORE PROFITS. It was not because it was better than aluminum!

As far as the OPs question, aluminum roofing does not need glued down, it is secured via screws around the entire perimeter, the middle floats. In fact it needs to float to allow for expansion and contraction with temperature changes.

The only places that will need screws is vents to hold the vents in place.

The perimeter screws are hidden via the trim pieces at the top of the walls.

The aluminum roofing is folded down over the side walls, then the top side wall trim is installed, a bead of butyl caulking is what is used to water proof between the roofing, walls and trim.

[badsix]

why not use the EPDM rubber roofing material used on most RVs. its probably not much more than aluminum in cost and probably easier to install. use Dicor self leveling sealer for any penetrations and you'll be good to go. I sure wouldn't want an aluminum roof with screws of any kind in it if I was looking for long life. Google RecPro, Dicor EPDM roofing
Jay D.

[theoldwizard1]

Aubrey0418 wrote:
So are you saying we'll have no choice but to screw it down?

ItsyRV wrote:
On my roof, (aluminum to wood & metal framing) they used 3M's Scotch Weld urethane adhesive. It was applied using the bead and roll method.

ItsyRV used an urethane adhesive which DOES have more flexibility than most adhesives. I assume by "bead and roll", he meant that a bead of the adhesive was applied to the wood (like where the rafters would be) instead of the entire surface (like a contact cement), the aluminum is then laid down and rolled.

I am no expert, but I think I would add the screws over the line of the adhesive. "Belts and braces !"

[theoldwizard1]

theoldwizard1 wrote:
Two big issues when trying to glue metal to wood.

• Preparation. The aluminum should be "scratched" a bit (ScotchBrite) and wiped down with acetone. Light sanding on the wood and a tack cloth.
• Expansion rates of the two materials. Aluminum expands a LOT when heated (sun exposure). Wood only expands a little when it is warmed. BAD COMBINATION ! No adhesive can survive that for long periods !!

Aubrey0418 wrote:
Also it's a 16ft camper so we will have to find a way to apply adequate even pressure throughout while laying the roof down..any suggestions on that?

Lots of cinder blocks or other heavy weights.

Best solution Hex self tapping stainless sheet metal screw w/sealing washer These will hold in plywood.

Shop for similar WITHOUT the rubber washer and you can buy those cheap.

[Aubrey0418]

theoldwizard1 wrote:
Two big issues when trying to glue metal to wood.

• Preparation. The aluminum should be "scratched" a bit (ScotchBrite) and wiped down with acetone. Light sanding on the wood and a tack cloth.
• Expansion rates of the two materials. Aluminum expands a LOT when heated (sun exposure). Wood only expands a little when it is warmed. BAD COMBINATION ! No adhesive can survive that for long periods !!

Aubrey0418 wrote:
Also it's a 16ft camper so we will have to find a way to apply adequate even pressure throughout while laying the roof down..any suggestions on that?

Lots of cinder blocks or other heavy weights.

So are you saying we'll have no choice but to screw it down?

[theoldwizard1]

Two big issues when trying to glue metal to wood.

• Preparation. The aluminum should be "scratched" a bit (ScotchBrite) and wiped down with acetone. Light sanding on the wood and a tack cloth.
• Expansion rates of the two materials. Aluminum expands a LOT when heated (sun exposure). Wood only expands a little when it is warmed. BAD COMBINATION ! No adhesive can survive that for long periods !!

Aubrey0418 wrote:
Also it's a 16ft camper so we will have to find a way to apply adequate even pressure throughout while laying the roof down..any suggestions on that?

Lots of cinder blocks or other heavy weights.

[ItsyRV]

On my roof, (aluminum to wood & metal framing) they used 3M's Scotch Weld urethane adhesive. It was applied using the bead and roll method. The roof section was also 8' X 16'.