DIYbanter - Metal Roof, Leaking at the lap joint screws

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Metal Roof, Leaking at the lap joint screws

My detached garage has a roof section that is a VERY low-pitch metal
roof.
Low, as in probably less than a 6' rise in 45 feet.
The metal panels are installed over tar-paper over plywood.

The metal panels are long enough that there are only 2 required for the
run down the pitch.

I'm getting consistent leaking across the roof at the 1st plywood joint
that's below the panel joint, most of the roofing screws at the joint
have their washer deteriorated and hardened, and some have been leaking
long enough that they are loose from the plywood rotting.

The amount of plywood that is rotted is limited to a small strip
running across the pitch, and only around the screws, and I am not
going to strip the roof to replace it.

My plan is to get new screws, and replace the screws where the wood
will hold the screw. Where the wood won't hold a screw, I plan on going
a little up & down the pitch (a few inches) and putting in a screw.

My question is, for the spots where the wood won't hold a screw, should
I put a bunch of roofing spooge on a new screw and shove it in the
hole, or should I fill the hole with silocone or roofing spooge?

Also, what is the likelyhood that water is migrating backwards up the
lap joint?
If its likely, should I raise the top panel slightly and apply roofing
spooge between the panels, or should I just apply some spooge over the
top of the joint? Ditto ques. for sealing tape (which I hope was used
in the 1st place...)

On the day I was on the roof, it went from sunny and 55 degrees to
cloudy, rainy, and about 45 deg., and I could see the panel joint move
by about 1/4 inch.

-Dave

Metal Roof, Leaking at the lap joint screws

According to :

My plan is to get new screws, and replace the screws where the wood
will hold the screw. Where the wood won't hold a screw, I plan on going
a little up & down the pitch (a few inches) and putting in a screw.

My question is, for the spots where the wood won't hold a screw, should
I put a bunch of roofing spooge on a new screw and shove it in the
hole, or should I fill the hole with silocone or roofing spooge?

Also, what is the likelyhood that water is migrating backwards up the
lap joint?
If its likely, should I raise the top panel slightly and apply roofing
spooge between the panels, or should I just apply some spooge over the
top of the joint? Ditto ques. for sealing tape (which I hope was used
in the 1st place...)

With such a low pitch, and especially if you're in snow country, I'd
assume that the water is wicking back up between the panels.

If you're not going to pull the panels, you're going to need to seal
_everything_ you can (with at least a 2 inch band under the overlap),
and probably goop the new fasteners you install. I think roofing
goop is the stuff to use, the silicone will fail. You have to get
the upper panel lower edge solidly anchored/sealed to the lower panel
with something that has some give.

Likely part of your problem is the upper panel "working" against the lower,
and wrecking the seals on the screws.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Metal Roof, Leaking at the lap joint screws

What opinions can I get about slipping membrane or felt into the lap,
under the upper panel and over the lower panel?

How about sealing old screw holes with aluminum foil tape?
Scary putting Al aganst Fe, but if I go for a temp fix for the winter,
it'd be removed in the spring.

Dave

Metal Roof, Leaking at the lap joint screws

According to :
What opinions can I get about slipping membrane or felt into the lap,
under the upper panel and over the lower panel?

If the material is the slightest bit porous, it'll make your leaking
problem worse rather than better. I think it's best to use the proper
roofing sealer goop. Especially if you're lucky and the sealer can
be applied above a purlin to minimize joint movement.

How about sealing old screw holes with aluminum foil tape?
Scary putting Al aganst Fe, but if I go for a temp fix for the winter,
it'd be removed in the spring.

The proper roofing goop wouldn't have the time limit. Foil tape probably
last longer than a year anyway.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Metal Roof, Leaking at the lap joint screws