What caulking to use for skylight/metal roof gaps? (leaking)

[s219]

Yep, Henry roof caulk products are the best!

 

[Oldpath05]

How about that Flex tape stuff where a guy SAWS a boat in half and tapes it back together then goes WEEE DOGGEEEEE...........

 

[Tractor Seabee]

I would use a silicone, with large gaps use a backer rod so that caulk is bridging gap and not trying to fill the gap full depth

Silicone is the last thing you want to use. It does not bond to a lot of materials. It will always peel off when surface applied. Use silicone only between two surfaces that are mechanically bonded; works as a gasket. The elastomeric uterthanes are the best. You have to get it at a building supply place that caters to the trades, you will not find it at the big box stores. Also backer rods with bond breaker is a must also. More of these type jobs fail than are done properly especially in residential work. Even architects doing commercial work specify the wrong materials and methods. Workers and even their bosses just do not know. There are two terms used erroneously: Caulking (cosmetic treatment) and sealant (what you want) and do not mix them up or you will get the wrong stuff. There are contractors that specialize in sealant work in the commercila and industrial world as smart general contractors know when to not tackle something.

As somebody has said; clean all the old stuff off first, that means down to the bare surfaces. Until then the proper application method cannot be determined.

Ron

 

[4570Man]

The last skylight I “fixed” I completely removed. It hasn’t leaked since. I was lucky and had a shingle roof and matching shingles. On a metal roof a decent patch would be harder. I agree with pulling that mess off and fixing it right.

 

[Piston]

Thanks for the all (surprising amount!) of the replies! Ideally I'd prefer to remove the skylights altogether, but I'll deal with a little maintenance every 5 years or so instead

I'll look around online a bit at the suggestions and see what I can learn.

What is best to use for filler material? Backer rod?

 

[oosik]

Back when we moved here and built our house - I made an enlightened decision. Our cedar log home was designed to have multiple skylights. At the last minute I chose to not instal any of them. One of the better decisions of my life.

However I do use caulk around my windows. In my part of the world I've found that - - DAP - ALEX PLUS to be the best, strongest and most long lasting of the many caulks available.

It is an acrylic latex caulk plus silicone and has a 35 year guarantee. It sets up harder than most and has an excellent ability to resist inclement weather.

 

[Redlands Okie]

Keep the silicone off the roof. Not only does it not work but after it fails the areas where it was applied will be hard to get caulking to stick. Acrylic and latex products can work better but still far from ideal.

Urethane products are the way to go. Brand of your choice. Sticks to a wide variety of surfaces, very adhesive, good flexing and stretching abilities. Holds up to UV rays from the sun real well. As others have pointed out correct application and use of backer rods is important. Once again, use a urethane caulk for good results.

It’s probably to late now but for feature work keep in mind that a properly flashed skylight, chimney, etc does not need any caulking to prevent leaks. A job using caulking to prevent leaks is going to be a ongoing maintence issue.

 

[oosik]

Huh - next time I need caulk - I'll definitely look for urethane products. Its been so long since I've had to caulk anything - urethane could have come on the market without my ever knowing about it.

 

[Tractor Seabee]

Thanks for the all (surprising amount!) of the replies! Ideally I'd prefer to remove the skylights altogether, but I'll deal with a little maintenance every 5 years or so instead

I'll look around online a bit at the suggestions and see what I can learn.

What is best to use for filler material? Backer rod?

It is a round foam product, comes in many diameters from 1/4" and up and is compressible. The places that sell the contractor grade sealants also have it. You can buy it by the foot there. Lowes is starting to only sell stuff in pre-packages instead of selling by the foot. Found a tube: the sealant I always use is "SIKAFLEX" 1a. They make a variety of products for the trades. 1a comes in the 10oz tubes and the quart tubes. I buy from Addison Supply here in Puget Sound, they are in Tacoma and Bremerton for us locals. Look up Sikaflex on the web for your local supplier. Addison supplies the concrete and mason trades primarily. They pre-fab re-bar to spec and drawings.

Ron

 

[EddieWalker]

The Sika line of products is sold at Lowes in the Cement isle. Sika Flex is one of many types of sealants that they have. Henry is the brand I recommended previously, and it's sold at Home Depot in the Roofing isle. I prefer Henry when dealing with metal roofs and metal flashing.

Both companies have websites that you can go do to read up on what they have available. You can also do searches and read reviews. Amazon probably has some good reviews once you decide on exactly what product you are considering.

If you fill the gaps with something flexible, that moves, you have to understand that what you use to seal it will also move. Movement leads to failure.

Caulking is designed for sealing wood type areas. Works great on Hardie too. It should NEVER be used on a roof. Same thing with silicone.

ONLY USE ROOFING products on a roof!!!

If working with a metal roof, ONLY USE PRODUCTS DESIGNED FOR A METAL ROOF and METAL FLASHING!!!!