metal building screws

[mechanic]

I have question for those who have metal building and experienced leaking screws.
I have replaced screws and used water proof silicone white because my roof is white each time to prevent the new from leaking. The screws that I removed looked like they should be sealing, but not taking a chance I double made sure by using waterproof silicone under the screw and around the washer making sure there is no leak. It is very hard to look for leaks when you deal with frost and condensation. I have a place along the wall that I'm sure is a leak so I plan to remove the suspicious screw and put in anew one using white silicone to make sure it does not leak. There is a product caled NP1 that is a polyurethane that I thought I would use but my research on line tells me that it would be very difficult to remove a screw that has this on it because it is like a rubber sticks very hard to the surface. My other thought would be to have spray foam put on the roof surface to seal all penetrations. I have vinyl back insulation on the inside of the ceiling that sometimes hides leaks. I don"t like getting on the roof because it is high and makes me nervous. I use rubber shoes when I do but still get nervous when I have to get up there. Have any of you had your roof sprayed with this stuff.
So my question is what method do you use in fixing leaks. Thanks.

 

[s219]

If the screw holes are the source of the leaks, it suggests two possibilities to me.

First, the gaskets on the screws could be poor quality. So try to buy a good reputable screw and don't cut corners.

Second, the screws could be getting put in too tight. There is a zone of "just right", where the gasket gets compressed a little, but not too much. In general, you want to screw down until the gasket just barely begins to bulge. This keeps the gasket shielded under the metal washer and out of sun and exposure that can cause it to deteriorate over time. If you drive the screw too tight, the gasket smashes down and bulges out from under the sides the washer. This will cause it to crack and break down from exposure, and leak.

I haven't had leaks on the metal roofs here at my new place but they are all less than 3 years old (I installed the roofs myself and was careful driving screws). At my old place I had to fix a few leaking screws and used a high quality GE silicone. In all of those cases, the screws had been driven down too tight by the installer and the gaskets became cracked and brittle. Rather than make a project out of it, I just shot a dab of silicone over those screws and made sure to work it in around the screw head.

 

[ruffdog]

It's good to OP brought up the condensation issue. If the air inside warms up and has enough humidity, moisture will condense on the inside when the metal cools at night. If it is leaking during a WARM rain, it won't be the condensation issue.

 

[gsganzer]

I assume you mean the self-tapping hex head screws with the integral washer. These are not all created equal, the best brand I've used are SealTite. These have a cap that helps contain the washer and prevents it from squeezing out. The other issue I've seen is people driving them to far in. You'll notice that in their catalog, they have a couple different types for metal to metal. Some are for fastening the panels to the purlins and others are a coarser thread for fastening trim to panels.

If the fastener is driven in properly and the washer compressed, you'd be hard pressed to have leaking there. Are you sure your leak isn't from where a screw fastens trim to a panel? The washer only seals on the outside where it contacts the panel or trim. If you have a place where water is getting between trim and a panel, you'll get a leak at the threads where it pierces the panel. (does that make sense?).

Your correct that finding a leak on metal roofs, especially if you have insulation can be a real pain.

You might also want to make sure you have an actual leak and it's not just a case of condensation that could be cured with some insulation.

 

[EddieWalker]

Screws are the number one reason for leaks on a metal roof. As mentioned, if they are too tight, the gasket doesn't seal out the water. When replacing screws, get them from a metal building company, not a box store. Tell them what you are needing them for. I get longer ones to make sure I get a good bite into the wood when replacing screws.

Silicone is terrible when used outdoors. It doesn't keep a seal on what it's applied to, and usually you can just peal it off, if it hasn't already fallen off, after a few years. Roofs are especially harsh on sealant products because of the extreme temperatures they endure. Add the movement of the metal, and it becomes a real challenge.

There are clear roofing sealants specifically designed to be used on metal roofs. There are other colors, but I'm not aware of one being white. Black and grey are the other two colors I use all the time. Henry makes a very good product that is sold at Home Depot. There are a few others, but that's the one I always have success with. Whatever you use, be sure it says on the tube that it's designed for metal roofs, or metal flashing on roofs. It will cost more then silicone, but not a lot more. I think it's $8 or $9 a tube.

 

[mechanic]

I'm going to try the Henrys. I called home depot and they have it in white. Do you know if you need to remove it does it come off without having to pull it off with pliers. I want it to stick good so it will work and if I need to reapply how's it come off?

 

[EddieWalker]

I've never ever tried to remove it. I've removed other stuff with a chisel. Be sure to read the instructions to verify it's for metal. Also check for the proper temperature to apply it

 

[PILOON]

I have plugged and patched a fair number of metal roof problems using a urethane caulking.

In Canada the popular brand is FLEXTRA which comes in about 24 colors.
A patch stuck on with FLEXTRA is almost impossible to pull off.

It is very similar in most ways to the sealant that they attach car windshields with.

Some years back the store displays had 1/4" strings of FLEXTRA butt stuck onto a metal bar on the edges of store displays.
Most folks would grab and pull on them trying to destroy the display. Well you could stretch that 6" 'cord' some 12-16" and it would not let go bot simply spring back.
I was meant to be a color display but served as a demo for the flexibility and adhesion.

A 4 X 4" patch covering a 2" hole on a metal roof would take a crow bar to remove it, that's how good a patch FLEXTRA makes.
It does emit an unpleasant odor as it cures but it cures fast. Comes is standard caulk gun sized tubes and sells in the $5.00+ range.

I'll add that it adheres to just about any clean surface including plastics and I have even used it to patch a hole in a new battery that I accidentally holed so it also is acid proof.
_______________________________________________________________________________
As to screws I always place mine on to top of the ridges using the screwgun torque setting to limit crush and never have had leaks.
Even back when metal was nailed rather than screwed they always fastened on top of the ridge. To me it is just logic.
But also remember that a metal roof will sweat often making you think it leaks while actually it does not.
Come spring with a snow load on the roof and nice warm days I actually think it is raining inside of my shed.

 

[crazyal]

My suggestion would be to go to a masonry store. They will have lots of different types of caulking. Tell them what you are trying to seal and they will set you up with an industrial quality sealant that will last decades.

 

[jimmysisson]

Some screws have a larger metal washer than others, maybe called severe service or some such. Those seal better and last longer as the rubber seal is shielded from the sun better. As said, too tight is as bad as too loose.
I would not spray foam under until I'd be sure there were no leaks at all. It will stop condensation "leaks" though.
Jim