Roof sag behind ac

[DanielM-TMO]

Newbie to the group. Purchased an otherwise great 2619, but with one problem. Was about to replace roof seal and noticed sag.
I know this topic has been addressed sometime ago, but I haven’t seen or am unable to find the fix for this other than the crazy suggestion to replace. The rest of the roof is in great condition, no leaks. It is the area directly behind ac unit. It has sagged down about an inch from horizontal. The wood that is used to install seal is solid. I’m thinking perhaps aluminum “c” channel bent into arch to match crown of roof with some minor trim mods. Has anyone come up with a solution for this. If not, I’ll be diving in the fall and will post pics of progress. I’m a skilled fabricator so it should be doable. Any thoughts, ideas or suggestions would be greatly appreciated.

 

[Shane826]

If you find a fix, please share. As of now the only fix is the crazy one you mentioned.

 

[rich2468]

Daniel,
I haven't done what you're proposing to do- raise the roof crown rear of the air conditioner, but I did build an aluminum box frame for my rear solar array and bent the box frame to be elevated above the crown.

I used rivnuts installed into the aluminum corner trim (at the edge of the roof and side panels) to fasten the aluminum box frame so that my six glass panel solar array "floats" a few inches above the rear shell.

With that experience in mind, I believe you should be able to accomplish what you've proposed, but I'd suggest keeping a few things in mind:
1: How much "lift"/ tension will you need to create to restore the roof crown? I'd try to get some kind of measure of the lift needed.

2: Will the above amount of lift be able to safely be transferred to the aluminum corner trim? You want the weight safely pushing down on the corner trim vs. pushing the walls out.

3. In consideration of the above amount of lift; you may want to consider a ladder type support to spread the lift force across multiple mount points on the front shell...but you also (obviously) need to be conscious of the support frame weight.

I have three aluminum box cross bars supporting about 85 pounds of solar panels; so each box frame bar is supporting approximately 28 pounds (or 14 pounds on each side) and that weight plus the box bars on the aluminum corner trim. These figures are all approximate, as my solar panels are arranged with the front two panels in a landscape orientation and the rear four in a portrait orientation.

The reason for sharing my array weight is to hopefully give you some kind of baseline of the amount of weight you may be able to support with a single c channel bar and help if you decide if you may want to try to spread the load over a couple of c channel bars.

For clarity, my TrailManor is a newer model (2021) and my solar array is mounted at the very rear of the rear shell. I'd consider the very front of the front shell and the very rear of the rear shell to be the most structurally sound parts of a TrailManor's roof due to the two sides being tied together by the front and rear end sections of shell.

Given that your roof AC unit weighs around 100 pounds, it might take 30 to 45 pounds of upward force to correct the sag at the front shell rear crown.



Rich and Lynn
2021 2922KB

 

[Bill-TMO]

Some time ago, one of our long-time members, Bruce Perens, found himself with a roof sag. To restore the roof to its correct profile, he started looking at possible methods, developing plans and designs in the process. Bruce is an avid radio amateur, and at the same time he fixed the sag, he also wanted to add some support for a bunch of ham radio antennas and such. He ended up with an external framework that was quite successful, if my memory serves. You can read some of his "how I did it" posts here - there may be more.

https://www.trailmanorowners.com/forum/showthread.php?t=19137

Bill

 

[DanielM-TMO]

Roof sag

Thanks to all of the TM folk for your timely reply. The sag is about 3/4” below a straight horizontal line in the 16” or so directly behind AC, so about 2-2 1/2 “ below the crown that’s on the rear roof section. That s nearly a 3” lift. I would be satisfied to get it back to horizontal. The AC unit is mounted within an inch of the front roof rear lip. It’s a big mother. (Kind of a crap design- mine is an 05 by the way) I’m thinking of an external box channel with some crown. As mentioned in a reply, the trick will be transferring load to side wall. Not sure what TM was thinking with wood framing in this area. I was actually thinking of doing side rails in aluminum also and installing as a unit. Not that big an engineering feat. Then we get into seal attachment. I’m thinking a bolt rope/keeder rail, aluminum extrusion that could be riveted to new frame then sewing new seals with bolt rope. Would make easier replacement down the line. As I said earlier, roof works now, so I think I’m just going to enjoy the next five months and fix it in the fall. I’ll post pics and materials when I tackle it.
In the meantime, if someone has an idea or suggestion, I’m listening.

 

[Bill-TMO]

Over the years, the Forum has had a lot of discussions about sagging roofs. Actually, a better term might be "squashed roofs", since they often happen due to snow load. One thing that has always concerned me is that when any arched or peaked roof is squashed to the point of flattening or dishing (sagging), the sidewalls that support it are splayed outward.

Whatever method is used to raise the roof to its original contour must also draw the sidewalls together, and keep them there. Interior cross ties at the top of the walls would do this, but of course the TM has no interior space for cross ties. This suggests that exterior support might be needed. Bruce Perens did this in the thread linked in a previous post.

My concern is that if an aluminum roof-frame member was originally fabricated with an arch, and later was bent in the opposite direction, I am skeptical that it could be simply bent again, back into its original curve, with its original strength. Aluminum doesn't like repeated bends.

I'm not a mechanical engineer, so I'm just noodling here. Gabled house roofs have collar ties to hold the walls together. In the 1800's, massive brick mill buildings in New England had thick iron cross-rods holding the walls together. Ancient stone cathedrals needed flying buttresses to hold the walls together if the wall-to-wall distance was too long for timber cross-ties.

I'm interested in any thoughts, from those whose knowledge is better than mine.

Bill

 

[DanielM-TMO]

I posted on this topic on a new thread with an exoskeleton idea someone had used for a different purpose. To all who check out this post, check out roof sag fix idea on a new thread
Thanks
Dan

 

[Kentmeyer89]

Wondering how this went. Any luck?

 

[Bill-TMO]

Kent -

You might try a PM to the guys who tried a solution, or an email if they included an address in their profile. They might not come back here to the topic, and so would not see your query.

Bill

 

[Wavery]

Newbie to the group. Purchased an otherwise great 2619, but with one problem. Was about to replace roof seal and noticed sag.
I know this topic has been addressed sometime ago, but I haven’t seen or am unable to find the fix for this other than the crazy suggestion to replace. The rest of the roof is in great condition, no leaks. It is the area directly behind ac unit. It has sagged down about an inch from horizontal. The wood that is used to install seal is solid. I’m thinking perhaps aluminum “c” channel bent into arch to match crown of roof with some minor trim mods. Has anyone come up with a solution for this. If not, I’ll be diving in the fall and will post pics of progress. I’m a skilled fabricator so it should be doable. Any thoughts, ideas or suggestions would be greatly appreciated.

I think if I ever had that issue:

#1 I'd get rid of the roof A/C. I don't think that the roof will ever be strong enough to carry the A/C again.
#2 I'd cut about 4, 1" thick roof ribs out of 3/4" of 4x8 sheet of marine plywood. The same length as original rear rib.
#3 I'd laminate 2 (or more) set's of 2 pieces of plywood together (with epoxy resin) to form 2, 1 1/2" x 1" thick ribs that are formed in the original arch.
#4 I'd use 1 rib in place of the original (damaged) rear rib.
#5 I'd place the 2nd rib forward of where the A/C was mounted. Maybe even one front of that hole and one rear of that hole.
#6 I'd replace the A/C with a normal RV electric vent.

Just my thought, rather than scrapping the old roof.

 

[Shane826]

I’ve had that thought and mentioned it to the factory… Instead of cutti bc a straight piece and flexing it to the shape of the crowned roof, actually cut arches out of wood.

Question… How would you insert the arches before or behind the A/C cutout?

 

[rickst29]

I'd use wood, with Laticrete HYDROBAN all over it.

Aluminum channel might be a bit lighter, but your need for bending will require that you introduce some "V" - like cuts into he stabilizing sides. Those will weaken the stability, and they might also develop into longer and unwanted cracks under the weight of the A/C unit (e.g., when hitting pot holes in the roadway).

With wood, you could build the curved shape more accurately. I would use a single piece of high quality wood, and I would paint ALL OF IT with Laticrete "HYDROBAN" after cutting the support into shape. (If you need to use two separate pieces for street versus curb sides of the roof "shell" paint Hydroban over the joint area as well - after they are joined together.)

Unlike most other "tile substrate waterproofing products", Hydroban maintains good flexibility and DOESN'T CRACK when the substrate moves. It can easily handle 1/16th to 1/8th inch of sudden movement stress within a tiny in a joint, and the overall flex of a support can be much longer than that. It stay slightly flexible for many years.( I live in Earthquake country, BTW).

Other paint-on watroof products, such such as 'redguard' (SP?) don't stay flexible. You will not find Hydroban at any big-box hardware store, you will need to go to a large tile/stone supply place which caters to pros in order to order a small quantity. I'll guess the minimum size sold is 1 gallon, even though you need only about a quart. Expect to pay well over $100 for that gallon.

https://www.laticrete.com/en/products/hydro-ban

 

[Wavery]

I’ve had that thought and mentioned it to the factory… Instead of cutti bc a straight piece and flexing it to the shape of the crowned roof, actually cut arches out of wood.

Question… How old you insert the arches before or behind the A/C cutout?

You would have to cut a 1 1/2" slot(s) across the inside of the ceiling. Remove the aluminum and foam. Then epoxy the plywood arch(s) in place (in the slots) by supporting the underside of the inverted roof to form the original arch and have the inserted arch(s) adhere to the aluminum and the foam. Also epoxy the cut-out aluminum to the bottom of the arch (inside the ceiling) to achieve the original thickness. It might be a good idea to make several of those arches so that you could put them under the inverted roof for shaped support.

In order to accomplish this, I would use micro-balloon filler to thicken the epoxy resin so that it would fill all of the voids between the arch and the roof and the foam.

Let it set for 24-hours, then cover the 1 1/2" cut-out aluminum slots with 3 1/2" aluminum strips, epoxy in place. Pop-rivet the strips on both sides of the slot(s) into the original ceiling.

If one were to put a replacement arch just forward and just aft of the 14" hole (for the air conditioner) it may even be strong enough to remount the A/C. Personally, I wouldn't do it. I would install a mini-split A/C instead.

 

[Shane826]

Keep in mind the hole in the ceiling isn’t 14”x14”. It’s a lot bigger so the control unit is recessed up into the A/C riser.

That said, if you did one behind the bag seal the rear of the A/C cutout is like 6”-8” forward of that so it might be a bit redundant at that point.

 

[Wavery]

Keep in mind the hole in the ceiling isn’t 14”x14”. It’s a lot bigger so the control unit is recessed up into the A/C riser.

That said, if you did one behind the bag seal the rear of the A/C cutout is like 6”-8” forward of that so it might be a bit redundant at that point.

The number and placements of the arch or arches would depend solely on the particular roof. All I'm proposing is a theory for a possible solution.

One thing that should be considered is that a roof that has collapsed probably ha delamination between the foam and the sheet metal.

 

[JohnUSA]

...If one were to put a replacement arch just forward and just aft of the 14" hole (for the air conditioner) it may even be strong enough to remount the A/C. Personally, I wouldn't do it. I would install a mini-split A/C instead.

Curiosity got the better of me. Where would you install a mini-split in a TM?

 

[Wavery]

Curiosity got the better of me. Where would you install a mini-split in a TM?

I just started installing one on my TrailManor Elkmont which is not as challenging as the folding TMs. However, it is quite similar as for placement of the equipment.

My original plan was to hang the condensing unit off of the rear but felt uncomfortable with that because it seems to be very vulnerable there and the road shock is much higher. I decided to install it on the togue. I will simply remove one propane tank when I run the A/C.

The air handler (inside part) will have to go under the forward cabinets which are similar to the cabinets in the folding TMs. We will just lose that storage space which is pretty useless anyway. I will have to drill many 2.5" holes in the bottom of the cabinets for fresh air inlet for the top of the air handler. I'll just open the cabinet doors when the A/C is running. My other thought was to hang the air handler about 4 to 6" below the cabinets but that may be ugly.

My placement of the refrigerant lines is pretty straight forward. With the folding TMs, you would have to have custom, flexible lines made up. The lines would have to have a couple of swiveling fittings as well. It's all doable, it's just a matter of how much $ one is willing to spend.