# A/C sinks into roof, fills with rain, Class C



## ezrv (Apr 25, 2011)

There is always a puddle around the roof a/c during & after rain. 
It seems that over the last 2 years the a/c has lowered itself, together with the aluminum sheet roof. 
So much in fact that the puddle level is higher than the sealed 1-inch a/c frame, the water passing through / over it, filling the ceiling, dropping onto the carpet. 

A new glass polyester hood covers the a/c. I duct-taped around 2 inches high after cleaning the surfaces of aluminum roof and hood with benzin / fuel. 
The water still flows, I have no clue where it enters.
The "sponge" ceiling may hold enough water to still drip even if there is non around the a/c. However, the main damage is really visible where the a/c is located. 

Planned corrective measure:
Mount 2 strong bars across roof, mount bars lenghtwise at the a/c frame.
Using threads to lift the a/c up so it will be higher than the edge of the roof. 

Has anyone here "lifted" an a/c the way I consider?
Has anyone had an a/c sinking the roof, causing a puddle around it, what done? 

Putting a big tarp over the roof won't help when traveling through rain. 

Thanks for helping.
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## frank-id (Dec 20, 2010)

Your roof must be raised by any method. A few nice 2 x 4s, 6, can make a strong back by securely bolting or screwing 2 pieces into a tee. The tee should be mounted on the outside from side to side near the AC unit, with another 2x4 on the inside with bolts, best bolts are carriage bolts. To assist in raising the roof, create a inside prop with several other 2x4s with a 24inch 2x4 at floor and ceiling. By starting the prop at an angle, th prop can be made to slowly raise the roof. A 2x4 and a hydraulic jack will slowly raise the roof. The 2x4 tee should look like the letter T inverted on top of the roof. Roof AC units are very heavy and nearly all roof leaks are caused by the roof sag. Frank in Idaho


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## ezrv (Apr 25, 2011)

thanks, I 'll try to attach a drawing, my idea. I don't fully understand your description, can not draw yours.
_mounted on the outside from side to side near the AC unit, with another 2x4 on the inside_

Inside there are cabinets on both sides. These may not be strong enough to support from the inside. My head would be above the bottom of the top cabinets. 
Driving over speed bumps may crash the a/c through the roof. 

given enough woodwork, lifting from the inside using my 4 ton jack should not pose a problem.
I think it won't stay up unless it is supported continuously. There is lots of water already collected in the ceiling, softening any wooden parts and beams. It shows in thin bubbles inside around the a/c from wall to wall.

I might have to delay repair to Nov-Dec when there might be no rain. Cover up the roof with a tarp and not drive while the ceiling is soft, and not drive in rain. 

Correction Post 1: Duct tape cleaning agent was gasoline, white.


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## ezrv (Apr 25, 2011)

drawing clarified, please discard previous version with older date
my message was Sep 3
Quote msg marker won't work in Quick / Advanced Reply


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## ezrv (Apr 25, 2011)

to Frank in Idaho
the way I understand our version is to have a (2) support "T" inside within the walkway, and leave it there.
I can't get your idea of the outside clear. You mean a "T" mounted to the wall? I would have to remove the awning permanently. 
I hesitate to assume that is what you meant. 
Vehicle is a motor home, not a resident trailer.

Please give it 1 more shot, may be then I "connect". 
There may be better ideas than what is shown on my drawing, else I would not have asked.


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## frank-id (Dec 20, 2010)

*Roof support*

Place one 2x4, the correct length, equal to the width of the trailer, on top of another 2x4. This will look as an inverter tee. Screw or bolt these 2x4 together. These bolted together will be either inside or on the roof. On the roof is preferred. After placing the 2x4 on roof, align the inside 2x4 with outer 2x4 and using long 3/8 carriage bolts, bolt the 2x4 together. Carefully drill thru the 2x4 to create a "strong back" to support the roof. All the 2x4s should be painted before final assembly. five bolts should support the roof nicely. A hydraulic jack and a few short 2x4s will raise roof temporarily as repair is made. This suppert has been used on several trailers and motor homes. After all is finished, some common roof tar/patch is added at all the area that the 2x4s touch the roof. At a later time the tar may be painted.
Frank in Idaho


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## ezrv (Apr 25, 2011)

*A/C sinks into roof, fills with rain, Class C - lift roof*

thanks Frank
I believe I understand now your solution.
I 'll try to attach a sketch of the way I understand your help. 
The page (5) is of lower quality than my original, file size reduced to meet upload limitations.

ezrv, Mexico


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## frank-id (Dec 20, 2010)

*Roof drawing is OK*

Your drawing has a few incorrect details as I have recommended. The tee beam is to be located on roof inverted. This is to not take away any walking space under beam. A single 2x4 goes inside directly under inverted tee. The top 2x4s are long enough to rest on each side. There are no 2x4s at sides of AC unit. All materials must be painted before final installation. The 2x4s on roof should have the corners cut at a bevel for a more pleasing look. Frank


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## ezrv (Apr 25, 2011)

*A/C sinks into roof, fills with rain, Class C - lift roof*

thanks, Frank
1) inverted T on roof: I keep reason in mind. 
2) the side beams inside may be stabilizing the lifting operation. Can be made removable. 
3) The rear beam inside has to be vertical for space reasons, between cabinet doors. 

New (drawing attached):
I consider adding sealing disks between wood and roof aluminum, to take care of unevenness and possibly the ceiling thickness variation after the job is done. 
Whether the bolt holes will be lined with a PVC pipe remains to be thought over. If there is any water inside the pipe it will not enter the ceiling but come out at the end of the bolt. 

I hope to find inox bolts and nuts of the required length, max. 1/2" thick. May be a problem. 

My language assistant for local stores inquiries: 
{Install threaded rod with a lock washer / Instalar la varilla roscada con una arandela de sujeción. 
From: 
threaded rod - Traducción al español – Linguee
}

E, Mexico


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## ezrv (Apr 25, 2011)

A/C sinks into roof, fills with rain, Class C
I am still in the planning stage, thinking through, step by step.
I bought 2 2x4"x8', found straight ones - a rarity at Home Depot, HD. These go inside.
The current stumble block is the joining method for the lengthwise beam along the A/C with the inner cross beam underneath the external lift beam combo. (Required because other hidden beams are wide apart, and A/C area is lower then these apart beams. (dwg2)
I have U-shaped joiners from HD, these don't l look like taking much weight sidewise. Plates might work, though so far I found no aluminum of 5-6 mm (<=1/4") to cut it from. I may have to obtain steel.

A set of drawings is here:
http://mostoepfel.tripod.com/mh_ac_lifter_20120928a p1-5.pdf
http://mostoepfel.tripod.com/mh_ac_lifter_20120928a p1-5.pdf
*dwg1* shows my initial idea collection, ignore for now
*dwg2* shows the layout to scale, new support beams located underneath the hidden roof beams. (brown, 41 cm apart). JOIN HOW is marked.
*dwg3* shows ideas about the lifting process
*dwg4* shows the joining problem with solutions, checks, etc. I thought I was done with it, then calculated the wood dimensions versus the space requirement of nuts and washers / disks. Result: No go.

*Alternatives:*
Dowels or similar. Problem is accuracy of drilling with hand drill. I can not recollect an instance where my wood doweling was precise and the result looking good. I guess I won't do this unless somebody pays me a big one in $.
Your alternatives: Please advise, thanks.


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After I log in again I get a "thank you" and a blank page
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## ezrv (Apr 25, 2011)

the drawings have been updated and file is here:
http://mostoepfel.tripod.com/mh_ac_lifter_2012.pdf

Unless something better comes up from the forum the "join" problem will be solved by using door hinges, possibly 90° rotated. This will eliminate cut out weaken the beam. It can be altered later with dedicated plates. 

http://mostoepfel.tripod.com/mh_ac_lifter_2012.pdf


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## ezrv (Apr 25, 2011)

*AC roof lifting - sealing problems*

Re beam joiniung: For the moment I go with hinges, door type. I 've seen some aluminum profile 2" wide. May be I go for this, replacing hinges at the end of the repair process. until then I hope finding something better.

The roof is sheet metal, bends and clicks to steps, assume supported by hidden wood. This small flexibility may be a cause for a new leak where the (5) bolts go through to the inside ceiling. My guess is that around the bolts there will be enough pressure around the bolt hole. But this is by no means certain because the beams spread the load. The pressure and lift force is applied between the outside and the inside beam, where ever it catches on the roof / ceiling construction. The location of these cross beams is defined by the beams inside the ceiling; the ceiling panels are screwed onto these hidden beams.
So there may be leak space around the bolts, invisible of course, and not accessible for caulking. 
I thought of adding automotive sealing washers (if I can find such) - there may be better ways coming forward from the forum - though the responses seem to have dried out - Frank is busy with his recent purchase, I guess.


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## frank-id (Dec 20, 2010)

*I am never too busy for a fellow RV owner*

Recently another guy with a class C, came over for a little direction. As is the construction of most class C motorhomes, his roof was really leaking for a whole year. After looking his project over, the decision was made to remove part of the ceiling. Most of the roof damage is at the rear vent and the opening for the rood AC unit. The roof openings were removed and a wood frame was constructed. The frames are 14.25 x 14.25 inside dimensions and constructed from material 1 X 1.5 fir wood. The frames were primed, then painted with good quality outside house paint. After the paint was dry, the frames were placed on the roof. Roof tar was placed between roof and frames. The frames were attached with 2.5 inch screws down thru the frames into roof. After the tar got hardened, more tar was used around frames to create a water tite seat. A few days later the roof was flooded with a hose for a while and no leaks. Currently the vents and AC are being installed. Strengthening the roof will be done where interior ceiling was removed. The new rafters are gonna be made of fir wood studs. The ends at the walls will be supported the blocking on the side walls. The blocking is gonna be a 2 x 3 with a little router work.
The side blocking will support the roof rafters and be screwed into every wall stud. The new ceiling will be the material used as shower surround in a bathroom. There is another forward vent aqnd may also get a new frame. Frank..........


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## ezrv (Apr 25, 2011)

many thanks, Frank, this is the kind of experience information I am looking for.
I won't go so far (yet), removing cabinets, a/c, inside ceiling, etc. One reason - I don't have the place to do it. Recently about u$1000 worth of tools got stolen from the house where I stored these for safety. Burglars cut the iron bars across one window during night, nobody home. There is lots of time when the area is unwatched. Then it is raining often, dry winter has not arrived, vehicle is under sky.

Progress:
The inside lifting process was very easy once I had all the wooden pieces with the right dimensions in place. The lifted ceiling now rests on 4 vertical posts until the outside top beams are ready for permanent mounting.

2 Outside beams (T): 
I could not find straight and unsplintered uncracked *treated* beams 2x4 at local Home Depot. I bought the same type I use inside. 4.5 x 9 cm. These will keep each other straight once fastened together. I have not bought the paint yet. The idea of using something else but the recommended oil paint is in consideration. I have to repair the metal roof seams with trailer roof seal "paste" and wonder if this stuff would be better than oil paint? I guess it costs much more. 

An idea has entered about wind slip of the top beams. As a T-shape across these will drag and use fuel. The current idea is to have glass fiber covers made in trapezoid shape by the same guy who made the a/c cover. Not water tight, condensing must be able to dry. 

I shall start a separate thread on a/c and condensation water, need some ideas, separate from roof lifting. 


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