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
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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.
Real Estate Broker · Cleveland Dayton Cincinnati Toledo Columbus & Akron, OH · Member since 2013 · 30k+ posts · 20k+ votes
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drilling a small hole for the camera would be the cheapest route. If you do not find anything you won't even need to patch it when your done. You can just use a blank outlet cover plate.
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
11y
Thanks all - I am having my tenant put a piece of tape on the wall when she hears the noise....trying to narrow down the exact locations. It has been a goose chase, and we are also trying to determine if it is a plumbing or HVAC issue. I'll let you know what we figure out... :)
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.
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
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@James Sinclair - Interesting. Were they using the A/C at that time of year? They are only running the furnace right now. I think I will call my HVAC professional and talk it through with him. Thank you!
Investor · Columbus, OH · Member since 2014 · 124 posts · 67 votes
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Is it weather related? We have a fairly new house that has downright scary loud knocks when it gets very cold out. We were told they were some sort of "expansion/contraction" issue. It only happens when it's very cold though, no other time. We were told it's normal.
Investor · Sacramento, CA · Member since 2014 · 308 posts · 94 votes
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In my current home we have two such knocks...
One is driven by a hot water pipe that expands when running the hot water in the Master bath and only when it is run at the sinks. The other is from our back door expanding during the day due to sun exposure and then cooling at night (that one gives us one knock during the evening depending on how hot the back side of our house got from sun exposure is what determines the loudness of the knock). You say it is the higher part of an interior wall, how close to the roof is that wall? Does that part of the roof face the suns direction? If it is only one knock my guess would be weather driven expansion and contraction. Just my two cents.
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
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@Chris Vail - interesting! I will check that out. The unit is a first floor unit out of three floors, so nowhere near the roof. Great ideas, thanks so much!
Investor · Atlanta, GA · Member since 2013 · 3k+ posts · 3k+ votes
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This may be a stupid thought, but do the upstairs neighbors come home late at night and maybe turn on their heater at that time? Then maybe that would correlate with previous posts of heat/cold expansion.
Minooka, IL · Member since 2013 · 353 posts · 85 votes
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Is there plumbing running near that wall? Could be hot water touching cold pipe and expanding and contracting. Also is this an exterior wall? Bathroom and dryer vent outlets can flap a few times a day outside with a loud smack sound. It could also just be a slightly loose nail warming up or cooling down and popping.
Contractor · Raleigh, NC · Member since 2014 · 651 posts · 510 votes
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@Jonna Weber I had a mystery sound once in a rental. It took me a while to figure it out but it turned out that some of the studs had pulled away from bottom plate of the wall (due to improper nailing and truss uplift). When the parts moved, it made a loud creak.
I'm not saying that's your problem but it might be something with the framing. Sometimes you just have to open up the wall to find out what's going on. It's only drywall, right?
Investor · Narragansett, RI · Member since 2013 · 8k+ posts · 4k+ votes
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Make sure you make it the tenants job to characterize the knock. Possibly tape record it, mark on the wall where it occurs and document frequency. A poorly defined noise is hard to fix. I had a beep for months with a tenant and she swore it was the property, turned out to be something entirely different and stopped when she moved out. I am not saying that is your case but I could have saved myself a lot of time if I had her accurately document it up front. Then you can look in the right place at the right time, not sure if it is in a pipe a camera will help but it is worth a try.
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
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@Sean Kuhn - No, we have not. So, I have my plumber scheduled to come at the end of the week to open up a small portion of wall and bring a camera inside the wall. I really am hoping I can narrow it down to something else before I have to do it, and will stop by again tomorrow to take another look. Thanks for asking! I will post a response when I get it solved!
Sounds like a "water hammer" issue in your plumbing. Probably you need to replenish all the plumbing system "air chambers" with air. Your plumber should be able to fix that without open any wall holes.
Here is a quick fix you could try:
1. Shut off your home’s main water supply valve
2. Open the highest faucet inside your house
3. Open the lowest faucet on the property and let it drain all water from the pipes
4. As the water drains from the pipes, air automatically replaces it.
5. The moment the water is completely drained from the piping, turn off the lowest faucet and reopen the main valve.
6. Air pushes out of the horizontal and open vertical water lines, sputtering as it exits the faucets inside. However, air remains in the air chambers, eliminating water hammer.
Investor · Boise, ID · Member since 2011 · 1k+ posts · 736 votes
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@Jeremy Shepherd - interesting! It is on an interior wall that is not near the dryer or the outside vent.
@Steve Olafson - I know there is plumbing, and probably HVAC in that wall. The plumber comes in with a camera on Friday. My HVAC suggested I it might have to do with when the furnace cycles on and off, but we haven't found any correlation. It sounds like a hard thump.. like someone dropped a book on the floor.
Investor · Crystal Lake, IL · Member since 2014 · 64 posts · 17 votes
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I had a knock in a wall of a SFR a few years back and it turned out to be the hot water pipes knocking in the wall because a pipe strap (holds the pipe to the stud) had come loose. Just a thought...... I also like Roberto Andrade's idea, that has also happened to another one of my houses in the past.