Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
I've had an issue in a condo I manage for a couple of months and after much trial and error, I thought I'd check with BP to see if anyone might have an idea what might be going on. The condo is a newer unit (2004) on a first floor. My tenant has been complaining of an occasional knocking sound coming from the upper half of an interior wall. We have run all the water in the unit and in the unit above it continuously, flushed toilets, etc. and have not found a correlation as to when the knocking comes. It also does not seem to be tied to when the furnace powers on and off. It happens more during the middle of the night than daytime, but daytime knocks happen too, and are getting more frequent. It is a single loud "knock" vs. a tapping. My plumber says that he would have to open up a wall to see if he can figure it out. I really am not looking forward to going that route, as I'm thinking there is a good chance he would not find anything. Thanks for reading!
Austin, TX · Member since 2013 · 123 posts · 27 votes
11y
I have had the tubing from outside A/C unit going to the inside unit do that. There was extra tubing that was coiled and when the compressor kicked on it shook the tubing.
Scottsdale, AZ · Member since 2014 · 659 posts · 536 votes
11y
It is not very easy to troubleshoot this without being able to see the situation. You did say it is a downstairs unit which leads me to believe that it might be upstairs.
Knowing what is inside of the wall will help. Are you sure that it is not coming from above the wall?
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
11y
Hi All -
For those that were curious - I had my plumber meet me over there today, and fortunately finally heard the "knock" myself. (I couldn't hear anything on 3 prior visits.) Before he even went to open up any wall, he assured me it was coming from the framing. The more we walked around the unit, the more we could get the wall to "talk."
His theory is that part of the reason it is noisier at night is because of the temperature drop causing things to expand/contract in the wall.
So - now the question would be....what next? I really don't want to open up a whole wall over something that may or may not be easily identified or remedied once open.
There is no danger (it is a 10 year old building and there are no settling cracks, etc.). it is simply an annoyance. Curious: What would you do?
Scottsdale, AZ · Member since 2014 · 659 posts · 536 votes
11y
That does not seem to fit the description given earlier about sounding like a book thump on the ground. Were you able to pinpoint the location? I personally would want it fixed. Perhaps some long screws that are strategically placed? You are right though, it is more of a bother than a concern.
Real Estate Investor · Elkhart, IN · Member since 2014 · 119 posts · 50 votes
11y
I would try what @Roberto Andrade suggested to see if that will fix your noise. As it sounds like a water knock from the description. It might keep you from having to open up the wall to fix the annoyance. Water know can get to a point where it will cause cracks in the copper pipe welds over time.
Contractor · Raleigh, NC · Member since 2014 · 651 posts · 510 votes
11y
@Jonna Weber What did you and the plumber do to get the wall to "talk"? Is this building 1-story or 2? Did it make the sound when you walked near the wall? If doing something makes it happen, that is a big clue.
My primary home would pop and crack loudly in the winter when the heat was running and causing things to expand and contract. I never did anything and ignored it. After about a decade it stopped :)
Rental Property Investor · Fredericton, New Brunswick · Member since 2013 · 7k+ posts · 4k+ votes
11y
@Jonna:
Is a "knock" like you hear in plumbing or does it sound more like ice cracking on a pond?
Are you having a cold spell in your areal of Idaho at the moment?
Loud knocks in the middle of a winter's night (when the temperature gets down in the -25 to -30 range) occur evan in some of our 100+ year old buildings. Materials expand and contract with the weather - and different types of material at different rates. This can cause a build-up of tension which get released (materials shift) suddenly making a knocking or cracking sound. This is more common in stick-built buildings, and does not necessarily mean things are breaking ... the building is just moving. It is possible you are hearing the sound via an interior wall or that wall may be the point where things are moving. Unless you are seeing cracked drywall, things are not moving much and the sounds are just part of winter in a northern climate.
[Note: I responded before arriving on page two of this thread. Glad to see you found your answer and I'm not surprised by what it turned out to be. I would wager that the framing in this building is acting like a thermal bridge it touches both the inside {warm} and outside {very cold} surfaces ... i.e. the building was not wrapped in a 1"-2" layer of rigid insulation before the finish cladding was installed to provide a thermal break between the exterior skin and the framing (skeleton).]
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
11y
Thanks for all the great feedback. Another reason I love BP.
@Roy N. - this is valuable information! I think your theory is pretty close to what is happening...except the weather is in the 30s right now, not negative temps. Like others said ..I do not understand why you would hear it in the interior wall instead of the exterior. In any case, I feel fairly confident I have at least eliminated the plumbing possibility.
@Account Closed - it happened pretty sporadically, but seemed to increase when we were walking close to the wall.
Real Estate Agent · Milwaukee, WI · Member since 2014 · 114 posts · 30 votes
11y
It is caused by the HVAC duct contacting when it cools so it is after the furnace in the upper unit has run for a while and then cools it knocks as is shrinks. look at upper unit where the vents are located and correlate them to the location in the lower unit.
Thanks for all the great feedback. Another reason I love BP.
@Roy N. - this is valuable information! I think your theory is pretty close to what is happening...except the weather is in the 30s right now, not negative temps. Like others said ..I do not understand why you would hear it in the interior wall instead of the exterior. In any case, I feel fairly confident I have at least eliminated the plumbing possibility.
@Account Closed - it happened pretty sporadically, but seemed to increase when we were walking close to the wall.
Have a great weekend!
Jonna:
If you are actually able to influence the occurrence of the noise by approaching the wall, it may well be movement between structural members (a loose stud) or between HVAC or plumbing work. The reason you may hear the sound on an interior wall rather than exterior, when temperature change is a factor would have to do with where the tension release point in the joined materials occurs.
That said, given your temperature changes are not extreme at the moment, If you have forced air heat, I would first explore the possibility the sound is HVAC duct work in the wall/ceiling (as Billy Bob suggested). The heating/cooling of the duct work as the furnace cycles can cause it to snap, crackle, and pop as it moves and tugs at its strapping.
Minooka, IL · Member since 2013 · 353 posts · 85 votes
11y
I wouldn't do anything about it. We all know for a fact its just something expanding and contracting. I too live in a ten year old house and as we speak my vents are popping when the heat runs. Also when I first run hot water in my bathroom sink on a cold morning I can hear the line popping down the wall on the sewer pipe. You'd be surprised how hard it will be to pin point the sound. Noise can travel through walls and if its just a nail popping you'll drive yourself crazy tearing out walls looking for it for no reason. All houses expand, contract, settle and rise. Nothing will be perfect and as long as its safe, its fine.
Investor · Atlanta, GA · Member since 2013 · 3k+ posts · 3k+ votes
11y
If she doesn't do anything about it, she might lose her tenant and might have the same problem with future tenants.
Crackling and small popping sounds may be fine, but bigger/louder pops that wake a person up would not be acceptable to me as a tenant.
I'm in a situation where my rented houses has an old heater that makes really loud popping sounds. My dog, who goes nuts about any shooting or firework or thunder sounds is deathly afraid of that heater sound. He will shake for hours when that happens and running back and forth to the backdoor, if it's closed, If it's open he won't come back in. Thundershirt doesn't help.
I would move, if I was in a colder climate. Luckily I'm in Southern California and we only had a few nights in the upper 30's. I shut off the heater and am now using an electric blanket on cold nights.
My point is that what may be acceptable for homeowner, because it's their house and they decide to live with it, may not be ok for a tenant, and they can simply pack up and move.
Lagrangeville, NY · Member since 2017 · 144 posts · 218 votes
7y
Does the second floor have any porches or decks on the exterior wall side of where this knocking sound is coming from? Perhaps you have an exterior deck/porch near that wall that is expanding/contracting due to the weather and making the popping sound. I Had a house with a deck that popped all the time when it got cold...
Rental Property Investor · Ocala, FL · Member since 2016 · 226 posts · 140 votes
7y
If there is CPVC water supply tubing in the walls, the hot water tubing will expand and contract. And, if it has tubing clamps over it, the CPVC will try to expand and move. When it finally does move through the clamp, it will make a pop sound.
If someone gets up in the morning and takes a shower, often the hot water tubing will pop.
Rental Property Investor · Morgan Hill, CA · Member since 2012 · 212 posts · 64 votes
5y
@Jonna Weber
We would hear popping in a basement when certain second floor fixtures were used, especially a particular bathtub. It turned out to be the metal straps for the horizontal drain pipe. A switch to plastic straps solved it.
Lender · Washington DC · Member since 2015 · 2k+ posts · 2k+ votes
5y
Can you find someone to spray in insulation at the point of the sound to buffer noise and perhaps cushion either a pipe or vent or framing that expands? Seems like a cheap fix. Drill small hole and pump in with a hose ? This won't fix a leak obviously