Tuesday, October 3, 2023


Preventing roof leaks – in a way you may not have considered

Courtesy: Motorhomes of Texas

Just about everyone who owns any type of RV has been told that they must periodically reseal all the areas on or near their roof to protect against potential leaks. There’s another potential leak source that is just as likely to cause problem leaks as those seams and vents. What is it?

It’s the seal of roof-mounted air conditioners. Those air conditioners sit on top of the RV but between them and the roof is a 14-inch by 14-inch gasket or seal. That seal is very thick – up to 4 inches – and the unit actually sits on top of the seal. Over time, the seal compresses under the air conditioner’s weight. With time and constant movement, the cooling unit can become loose in its mounting hole through the roof and voila! – a potential leak.

It’s usually very easy to access the bolts that snug the air conditioner to the roof. This is done by opening or removing the interior return grille on each unit, thus exposing three or four through-bolts and nuts. In turn, this hardware can then be snugged down with a socket, ratchet and extension – tools that almost everyone owns.

A leak created by a loose air conditioner can easily traverse the interior of the roof and drip out in areas far from the leak, complicating efforts to determine the source. Checking the tightness of your air conditioner should be on your list of maintenance items to be checked yearly. It could save you lots of dollars.



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Larry Fuchs
1 year ago

Once again we get a half tip. The author fails to address ducted air conditioners of which I’m sure many readers here have that type, and where to find the hold down bolts

T Edwards
3 years ago

WOW! Checked the 4 bolts securing the AC to the roof on our 10 year old KZ and found they were all loose by 1/4 to 3/4″ . Looked for water damage. None found. The weight of the AC against the gasket apparently provided enough compressive force to form a water right seal. I’ve tightened the bolts and add to my maintenance check list.

3 years ago

Silicon sealant is the worst thing you can use. Although it sticks to everything,it always doesn’t do it well. Dicor makes sealant that flexes and both self leveling and regular. And it cleans well.

Donald N Wright
3 years ago

Chuck, While I have a Cool Cat on my Aliner (with a list of problems) I have wondered why Recreational vehicles do not have a central heat and A/C system like houses do ? Why are A/C units up on the roof ?

3 years ago

Excellent question Don! I’ve wondered this too. My 1994 Winnebago Vectra has the A/C in the basement with ducting thru the ceiling and it works beautifully on either 30 or 50 amp. It is fast, efficient and relatively quiet too! We can also just run the fan without the cold air. We love it! So, to your question – Why not?

The furnace is also ducted under the floor with some heat into the basement as well.

3 years ago

We have ducted air conditioners, therefore nothing is exposed inside the camper. How are they fastened to the camper? Where are the fasteners located?

Dale e Rose
3 years ago
Reply to  Charlie

Remove the air intake where the filter is located, in the ceiling. There are usually 4 screws that hold the cover, 1 in each corner. I had a leak from my a/c last week, and I found that the hold down bolts were loose.

Gayle V.
3 years ago
Reply to  Charlie

Hi Charlie, I too have ducted air, with no inside access. Mine are fastened with 4 lag bolts per unit on the roof. You will have to remove the cover (obviously) to gain access.
I always double check the bolts when cleaning the fins.

3 years ago

I learned this one the hard way during a monsoon rain in Arizona. The bolts on both air conditioners had no torque on them at all. One point not mentioned in the article is that these bolts do not get much torque at all, so make sure you follow the OEM torque spec. You do not want to overtighten them.

Janet blaes
3 years ago

We just bought a used KZ Sportsman and the very first thing we did was remove all the caulk on the roof, seams windows and door. It does not have a rubber roof but rather a metal roof so we removed some of the self leveling caulk and added more where needed.
It was a lot of work but now the entire camper is sealed. We also applied silicone to the seams of the bath tub area and kitchen sink area. I think we will be good for a bit.

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