Hi there,

We have a fourplex with a flat roof in Calgary, Alberta. The building was built in 1977, but the roof was redone a couple years back before I moved in (gravel-top).

Last winter I was startled awake quite a few times by a loud bang that sounded like someone was swinging a hammer on the roof. It would happen in the middle of the night usually, and happen between ever 10-40 minutes it seemed. It didn't seem to happen during the day. Through the spring/summer I don't think it happened once, but now that the temperature is getting cold again we've noticed it over the last few nights. It started early tonight at around 9PM (which is earlier than normal.. usually it's about 1-2AM).

I'm thinking it's fairly obvious that it's related to expansion/contraction of something in the roof, but my question is what can be done to fix it? It's to the point where I'm sleeping in the basement to avoid being startled... would getting a roofing contractor to come and look at it be worth the time?

One last interesting thing is that it didn't seem to happen when there was a good amount of snow covering the roof (insulation/more constant temp??).

Thanks so much to anyone who can offer guidance.. I'm going nuts here..

When you say gravel top do you mean a rubber membrane with rocks on it, or hot tar roof with rocks? I had a similar problem a couple years back but the roof was a Carlise Mechanical fasten in a high wind area. The customer was too cheap to go with a high 90 mechanical fasten so the rubber bounce up and down on the iso making loud bangs.

smebobo wrote:

Hi there, We have a fourplex with a flat roof in Calgary, Alberta. The building was built in 1977, but the roof was redone a couple years back before I moved in (gravel-top). Last winter I was startled awake quite a few times by a loud bang that sounded like someone was swinging a hammer on the roof. It would happen in the middle of the night usually, and happen between ever 10-40 minutes it seemed. It didn't seem to happen during the day. Through the spring/summer I don't think it happened once, but now that the temperature is getting cold again we've noticed it over the last few nights. It started early tonight at around 9PM (which is earlier than normal.. usually it's about 1-2AM). I'm thinking it's fairly obvious that it's related to expansion/contraction of something in the roof, but my question is what can be done to fix it? It's to the point where I'm sleeping in the basement to avoid being startled... would getting a roofing contractor to come and look at it be worth the time? One last interesting thing is that it didn't seem to happen when there was a good amount of snow covering the roof (insulation/more constant temp??). Thanks so much to anyone who can offer guidance.. I'm going nuts here..

The roof was hot tar/rocks. It actually seems to happen the most when it's very calm outside and the temperature is dropping. And when I say it's loud, I mean LOUD... some thumps are louder than others but the biggest ones shake the whole house and quite literally sound like someone is up there with a 50lb sledge hammer.

We had a client that complained about exact problem you described. He bought the house with a tar and gravel roof on it.In mid winter when the night temps dropped rapidly he would sometimes be awaken from sleep with the loud banging noises.
We replaced the roof as it was nearing the end of its life cycle and with the new roof we installed 3 inch iso insulation. that was two years ago and the loud banging noise has not happened since adding insulation.

I have the exact same problem you have described. Did anyone tell you any quick fix for the problem, besides getting a new roof? It's driving me crazy.

I have a very similar issue with a with a roof of the house I’m about to buy..
The house is in Los Angeles area. Roof if flat and was redone last December (only few months), but it was installed on the top of the old roof. This noise is so bad because it sounds like someone is walking on the roof! We haven't slept in this house yet, but it sounds like this noise appears usually in the morning (when sun starts to warm up the roof) and after the sun goes down and roof cools off. We are not sure if this is something that might settle after few months or we would have to do the roof..
New roof that was installed is a APP Membrane. I'm not sure what was installed there before. Any ideas what I should be doing?

i had an experience where a customer heard banging sounds coming from the roof, it was a family of raccoons living in the crawlspace between the ceiling and the roof deck. they burrowed in the insulation for the winter.

Over the last 10 years I have investigated this same situation on several flat roofs. Sometimes it was due to lack of fasteners holding down the iso and sometime it was movement of the plywood. Even had iso in hot do the same. Often it is a poping sound that seemes to be coming from the iso. Once concern is the new blowing agents used in making iso...could they be causing the problem sound? I also would like some ideas as to the cause of the problem and a solution. Oh, don't add dumb comments on this topic (not that anyone would)....it is actually a real problem that needs to be solved by this roofing community.

i had a sloped shingle roof we did 3 years ago that did it for the last 2 springs for a few days. Could not figure it out. We did nothing different than the other 5000 roofs
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I have a feeling its related to some sort of reaction going on with the plywood or joists. Around here it seems only to happen with extreme cold temps during the night, and with little or no snow present.
I use to go winter camping some years ago and I remember a few times being awaken by a very loud crack or bang, we would go outside thinking maybe an animal had knocked over our equipment but everything seemed to be fine.
We were later told by a old timer who travelled frequently in the winter wilderness that the loud exploding noise was a result of a tree actually splitting open from expansion when the temperatures dropped well below zero.
The temps were usually below -30 celsius at night.

I have spoken to some engineers and they are saying it might be possible to loosen some joist on the side of the house to let the roof have more room for expansion.. Instead of redoing the roof.
Others say that we need to redo the roof.. As the problem could be because the old roof was not removed and may not be properly attached to the frame of the house and could also have some damaged wood underneath. I was really hoping that I can avoid re-roofing... especially that the roof is 2 months old, but again few days ago I noticed that the new roof already has a small hole on the edge and the water is there already and leaking.. luckily our house has extended edges so the leak is not inside.. but the wood under the roof material is all wet and leaking.. so that tells me that the new roof was not done by the good roofer! And does not leave me a lot of confidence about this roof although it is new..

Also, temperatures here in Los Angeles are not that low.. in winter it can get as low as 40 but that would be it.. For instance, now days it is about 50 degrees at night and 60-65 during the sunny days.

My advice before hiring a contractor is to access the roof on a weekend night, and wait for the sound to occur. You say it happens in intervals, so spending the time up on the roof locating the spot would be very beneficial. You could have anything from expansion/contraction issues, to animals, membrane flutter, illegal immigrants living on the roof (don't laugh, I've seen it but typically it happens on shopping center roofs with half-ladder mounted on wall or other access point), etc.
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Professional Roofing & Waterproofing Consultant

haha, illegal immigrants well, we are planning on moving in after the remodeling. so i may delay with a roof and do it after we move in and live for some time. i guess at that point the most important thing would be to properly fix all the joists before putting a new roof. it almost sounds like you want to make them tighter but not as tight so they would have room to move when expanding..