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 > Adhesive for Aluminum roof to plywood?

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PNW_Steve

Pacific Northwet & cold

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Posted: 01/04/20 04:49pm Link  |  Quote  |  Print  |  Notify Moderator

Another option :

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


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Huntindog

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Posted: 01/04/20 06:01pm Link  |  Quote  |  Print  |  Notify Moderator

Quote:

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.


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badsix

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Posted: 01/04/20 07:36pm Link  |  Quote  |  Print  |  Notify Moderator

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 ^ [emoticon]

[emoticon][emoticon]

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

Gdetrailer

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Posted: 01/04/20 08:07pm Link  |  Quote  |  Print  |  Notify Moderator

Huntindog wrote:

Quote:

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.

Gdetrailer

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Posted: 01/04/20 08:11pm Link  |  Quote  |  Print  |  Notify Moderator

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 ^ [emoticon]

[emoticon][emoticon]

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..

Huntindog

Phoenix AZ

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Posted: 01/05/20 02:10am Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

Huntindog wrote:

Quote:

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


NRALIFR

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Posted: 01/05/20 05:15am Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

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 ^ [emoticon]

[emoticon][emoticon]

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..


Well, no offense intended, as all I know are the three TC’s I’ve owned. The 19 year old Lance In my sig, and two Jayco TC’s before that. All had a seamless aluminum roof, and there was definitely more than just the aluminum up there. Probably because TC’s don’t sit on a steel frame like a trailer, and their roofs are usually intended to be walked on. But, the construction of the trailer they’re rebuilding sounds very similar.

The only TC I’ve had to open up the roof on is the Lance, and there is a layer of some type of insulation between the aluminum roof, and the layer of plywood or luan that’s on top of the ribs. The voids between the ribs are filled with more insulation, then the ceiling plywood is on the inside.

The OP’s trailer that they are rebuilding also has plywood over the roof ribs, whether by their design or the OEM. If it were my camper, I wouldn’t try to adhere the aluminum to the plywood, but would put a thin (~1/8”) layer of some type of felt or foam insulation between. Mainly because I believe it will help quiet the roof when it rains, but it may also have some benefit in preventing condensation.

[emoticon][emoticon]


2001 Lance 1121 on a 2016 F450


wing_zealot

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Posted: 01/05/20 06:46am Link  |  Quote  |  Print  |  Notify Moderator

There are literally millions of metal roofs screwed down to wood substrates. You use specialty screws designed for that purpose and install them properly. Why re-invent the wheel. Follow the manufacturer's directions.

GrandpaKip

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Posted: 01/05/20 08:58am Link  |  Quote  |  Print  |  Notify Moderator

There are thousands of screws in the metal roof of my house. Never had a leak.
There are lots of screws in the roof of my camper. No leaks.
Every boat I’ve owned has had screws or bolts in the decks and coach roof.
Properly installed and maintained, screws are not really a problem.
Unless y’all aren’t going to have anything go through the roof, I wouldn’t worry about it.


Kip
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ItsyRV

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Posted: 01/05/20 09:56am Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

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 !"

The uncovered roof surface was metal framing along the sides, leading and trailing edges. Two additional metal ribs were placed at the air conditioner. Some of the bridging was also metal. The remainder of the ribs, bridging and attachment supports were wood. Between all this was the standard rock solid foam with a thin wood top surface.

The two part urethane adhesive was applied to the metal framing in a thick bead. The reminder of the surfaces had another type of thing lightly sprayed over it. I have no idea what that was. The aluminum was attached at leading edge with screws through the transition. As it was being laid down, a heavy floor roller was used to ensure contact and to make sure it was tight with no ripples, bulges or indentations. The edges of the roof (front, back, sides, and around the a/c opening, were screwed down through the transition and edge pieces. I did not get to see everything they used or did but was able to see enough.

Years later you can walk on the roof with no flexing at all. It's as if its one solid roof. There is no separation between the aluminum and the surface underneath. I belive they actually used three different adhesives; wood to wood, wood to metal, metal to metal. As a way of clarification, this was not done at an RV place but by those who service those emergency command type vehicles and trailers.


1994 Itasca SunDancer 21RB - Chevy G-30 chassis.


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