Used Karnak Karna Flex WB Elastomeric Mastic on cracks on the membrane with recommended polyester fabric sandwiched in between for roofing repair.
I’m thinking of using this product or seeking your suggestions for another method in making repair to my skylight.
Last year I made the mistake of spraying around my skylight perimeter with one of these new rubber spray “solutions”. The idea was to fill the cracks in my hot melt roof (modified bitumen membrane) as a winter emergency.
Instead, I found after hurricane Joaquin gave us heavy rains, that my work last winter had cracked, and as I pulled some of the material away from the base of my skylight today I found water was trapped in between. The material seemed firm, and I saw no mold or rot. So I used compressed air to blow excess water out and speed the drying. Now I’m left with some of this spray rubber well attached to either the roofing material or the metal base of the skylight, or some craters or holes that I would hope to fill while somehow making a good repair to this skylight perimeter before it rains this Friday. So I hope to make a repair tomorrow, about 18 – 20 hours since having touched this area today.
It seems it would be difficult to remove all the spray rubber, and may not be necessary since in many places it seems firm and well bonded.
Problem may be that the depth of these dimples or craters may exceed the 1/8 inch maximum that Karna Flex may be applied per the manufacturer.
Any guidance for this approach or better methods/materials would be appreciated. Thanks.
Replies
Skylight repair
I used to try and repair leaking skylights (1 or 2). It didn't take me too long to work out the easiest method to repair leaking skylights was to replace them. Unless you get really lucky, you'll just keep coming back onto the roof with mastic trying to patch a hole that you can't find. Once water gets in there, it seems to heat, evaporate and expand the space every day when the sun is shining in summer and freeze, make a mess in winter and blow through all the seams. You need to eliminate that water as I'm sure you are aware, and you really can't get at it all unless you remove the skylight. With the rains coming, you can do a temporary patch, but you will need to address the situation as soon as the sun comes out again.
Regarding your roof slope: I might be reading too much between the lines, but your comment appears to indicate to me that you have a self-flash skylight frame on a low pitched or flat roof. Self-flash frames are recommended on 3:12 roof pitches or greater. Curb mount skylights are far better on low sloped or flat roofs because the flashing can be better integrated into the roofing. If you have 3:12 or greater, replace the skylight with another self-flash. You might consider even with a 3:12 or greater pitch, taking the time to construct a curb and have the skylight manufacturer either supply or make up a flashing system for you as well. With a local acrylic skylight manufacturer, you should be able to ask for a completely welded aluminum curb flashing for a flat roof with an extra wide base and welded joints all round. It'll be saved time and effort in 15-20 years and in my experience, roofers are far more familiar with curb mounts than they are with self-flash frames when it comes time to replace the roof. Follow the instructions from the manufacturer. If it's an aluminum framed, acrylic dome skylight, I use a good coating of Geocel, or similar specialized caulk under the base of the skylight or flashing and securely mount it to the decking. Mastic is okay, but I don't like using it. It always seems to crack with age and the Geocel holds up much longer.
When you order a new skylight, either take the old skylight into the manufacturer or report the inside frame dimensions. If you're getting a curb mount made up, you'll need the dimensions of the rough opening. The manufacturer may ask a few more questions of you to get the right product for you or just add about 3-1/4" to the rough opening dimensions to get the outside curb dimensions with a little allowance for flashing.
I hope this helps. Good luck.
Thanks. I never had any water that I could detect as coming into the home structure or beneath any roofing material. It may simply have been cracks in muck around the skylight that I saw. Anyway I have a curb style skylight as described to me my roofers who inspected for a potential roof had told me. After blowing out and drying any trapped water from my previous work, I found the surface to be solid and dry and figured until a new roof may be gotten I should be good with what I did. Will keep an eye on it. For now I've followed the manufacturers directions and will hope I'll be good for at least this winter season. I don't think the skylight ever leaked. The cracks I've seen along vertical roof membrane I'm guessing are on the outer most recent roof that was applied. I found no sponginess on the roof if water were trapped between layers. So I figured best to seal these cracks and I did so. I will have to probably get a new roof sometime in about a year, but I will get some professionals to look at it then - problem is finding good honest people with a solid background for doing that. I've gotten very little transfer of serious knowledge from people who've been on my roof before, most of them just want to sell you a new roof. Thanks for your input - probably useful when it comes to having to replace the skylight I be able to raise better questions to the person who will do that work.