Questiones to the Conrators Floor Creaking

[Chestnut]

There are some of you out there that are very knowledgeable on house construction so i thought I'd throw this out there.

I live in a 4 level split house that was built in 1991. Talking to the original owners they made it seem like it was a custom house and from the quality of some of the construction it seems that it wasn't a slapped together starter house. I don't know how much that matters. The sub floor above my shop is OSB, so i assume that it's the same throughout the house. The joists are solid 2x material, my guess is 2x10 throughout. I do have blueprints from when the house was constructed if that information would help let me know. They are more architectural in nature and i don't believe they show hvac but they do show studs & joists, as well as sizes and spacing.

The problem is this winter after the forced air heat shuts off there is loud creaking that follows. It's not really a problem other than it wakes me and Megan up in the middle of the night. It sounds exactly like the creaking that results from walking over the creaky floor just outside our room or in the two adjacent bedrooms. This is the problem we wake up think the worst and then have a hard time falling back asleep.

Could the sub floor really be expanding and contracting that much from heat alone? I know wood moves from moisture but never thought much about temperature movement. I assume that it does move from thermal variation but never thought it would be enough for what we're experiencing. The problem  has only existing in the winter the AC does not cause the same sounds. Also to note we haven't really noticed it during the day, only at night. This is not to say it doesn't happen during the day, it's just not noticed.

Could the creaking be occurring from the ducting? It doens't sound like metal shafting on metal. It sounds like someone is walking through a house from the early 1900s with a creaky floor, i know what that sounds like because i had one of those. The area that is creaking is carpeted on the flooring side and the floor below it is drywall. There is a cold air return running somewhere in the vicinity in the floor just not sure the specific layout. I'm not sure of a possible solution for this. I don't really want to go around driving nails in willy nilly for fear of hitting something. I also don't have experience stretching carpet and i'm not sure i want to hire someone to do it. If the carpet comes up it's probably going away for good and hardwood is going down. I don't really want to tackle that investment at the moment.

Summary: Have a creaking floor after furnace quits.

Could the sub floor really be expanding and contracting that much from heat alone?

Could the creaking be occurring from the ducting?

Possible Solutions?

[Tom King]

Too many variables without being there.  I'd bet not the wood, or sheathing.  What type of ducting, and is the return duct large enough to get into at all with the filter out?   What type of water piping?

[wdwerker]

Could be a duct shrinking as it cools off and it's rubbing on something.  Many tool rental places will rent carpet kickers, power stretchers etc. I'm sure there are YouTube videos on carpet. If you pull up the carpet just a little in a corner that will let you see what's under the carpet & pad. If it's just plywood or OSB you can work and hunt from above. I have used a nail puller to remove the sheet & give access inside the floor system. 

This pic is from Walmart $38

You can buy or rent inspection cameras that will let you look under the floor by inserting the flexible cable through a small hole. Then you can start eliminating the areas with no mechanical systems under the floor.  Figure out how to force the noise to occur then happy hunting.  I have used my osselating multimaster w a saw blade to cut a section out of a subfloor to gain access without removing an entire sheet.  Some sheets may continue under interior walls. 

But your set of conditions is totally wishful thinking.  Figure out how to force the noise to occur , then try to track it down to a localized area. Then gain access and figure out a cure. Might have to cut a little clearance room for the duct or fasten the duct differently. Maybe slip some rubber or silicone sheet into a contact point. Happy hunting. Tracking down intermittent noises in a house takes patience.

[Chestnut]

1 hour ago, Tom King said:

Too many variables without being there.  I'd bet not the wood, or sheathing.  What type of ducting, and is the return duct large enough to get into at all with the filter out?   What type of water piping?

Yeah i figured there are a lot of variables. I wish i could record the sound it makes because it doesn't sound metallic in nature at all. I realize that a duct could pull on adjacent wood but most of the time when i hear that happen I still hear a metal ping along side the creaking wood.

Return duct is  probably just a sealed of joist if the construction style is similar throughout the house so 16" x 10" > Not really accessable for a person from the filter but i could get a camera in from the return in the bedrooms. I don't have a flex camera but there have been a lot of times I've wanted one.

Water piping is copper. Nearest water pipe is probably 15' horizontally form where the sound comes from.

54 minutes ago, wdwerker said:

Could be a duct shrinking as it cools off and it's rubbing on something.  Many tool rental places will rent carpet kickers, power stretchers etc. I'm sure there are YouTube videos on carpet. If you pull up the carpet just a little in a corner that will let you see what's under the carpet & pad. If it's just plywood or OSB you can work and hunt from above. I have used a nail puller to remove the sheet & give access inside the floor system.

This pic is from Walmart $38

You can buy or rent inspection cameras that will let you look under the floor by inserting the flexible cable through a small hole. Then you can start eliminating the areas with no mechanical systems under the floor.  Figure out how to force the noise to occur then happy hunting.  I have used my osselating multimaster w a saw blade to cut a section out of a subfloor to gain access without removing an entire sheet.  Some sheets may continue under interior walls. 

But your set of conditions is totally wishful thinking.  Figure out how to force the noise to occur , then try to track it down to a localized area. Then gain access and figure out a cure. Might have to cut a little clearance room for the duct or fasten the duct differently. Maybe slip some rubber or silicone sheet into a contact point. Happy hunting. Tracking down intermittent noises in a house takes patience.

I'd love to tear up the sub-floor but i fear it's construction adhesives to the joists. I can see adhesive used in the floor above my shop. That's not to say the guilty section couldn't have worked it's way loose. i think it has because there are creaky spots walking over the floor.

[Tom King]

Get some trim head screws, and run some down through the carpet to pull the sheathing back tight to the joist, where you can find a squeak from walking on it.  I wouldn't bet on that fixing this issue, but it would be a simple try.  Depending on the type of carpet, you might even be able to use Deckmate screws.  It all depends on if the head can pull down through the carpet without pulling the carpet.

[wdwerker]

I have drilled a hole and squirted construction adhesive into a gap then screwed it down. But an AC related noise probably isn't a floor squeak.

[Tom King]

It might even be all the way back at the air handler, and the sound goes through the duct.

[wdwerker]

Yea, didn't think of that. Cooling heat exchanger could creak. Is it a gas, oil or heat pump type system?

[pkinneb]

Drew not that it helps but our house was built in early 2000's and my wife and I think it is abnormally creaky as well if you do find the culprit let me know, I will do the same. So far I have checked the water pipes to insure they are tight to the joists, and have been checking the heat ducts as well. Our floors are engineered I beams and I have been finding and fixing squeaks from those like suggested by Steve and Tom with construction adhesive and screws. but still feel we have a lot of creaking for a relatively new house.

[Tpt life]

Likeliest areas are hottest and coldest. e.g.

Plenum heat often allows for hottest floor joists and other framing members. Pooling ceiling heat leads to truss expansion and center lift. 

Drafty areas or poorly insulated zones lead to rapid cooling. 

These kinds of areas lead to the most change. Cracks are far more common than creaks. 

[Chestnut]

29 minutes ago, wdwerker said:

Yea, didn't think of that. Cooling heat exchanger could creak. Is it a gas, oil or heat pump type system?

1 hour ago, wdwerker said:

I have drilled a hole and squirted construction adhesive into a gap then screwed it down. But an AC related noise probably isn't a floor squeak.

Would finding a joist and shooting it with 18 ga  2 1/2" finish nails work? They might not lodge in the carpet like a screw would. I'll have to try the screw thing tonight and see how it goes.

40 minutes ago, Tom King said:

It might even be all the way back at the air handler, and the sound goes through the duct.

Didn't think of that. It's a natural gas forced air. If it was that loud coming from the heat unit you'd think I'd hear it when I'm standing right next to the unit in my shop when I'm working with hand tools.

I wish i knew what the ducting was made out of. Most of it in the basement is the flex type. Some is solid.

2 minutes ago, pkinneb said:

Drew not that it helps but our house was built in early 2000's and my wife and I think it is abnormally creaky as well if you do find the culprit let me know, I will do the same. So far I have checked the water pipes to insure they are tight to the joists, and have been checking the heat ducts as well. Our floors are engineered I beams and I have been finding and fixing squeaks from those like suggested by Steve and Tom with construction adhesive and screws. but still feel we have a lot of creaking for a relatively new house.

I honestly wouldn't care if it didn't wake me up in the middle of the night thinking i need to make a frantic grab towards my night stand.

1 minute ago, C Shaffer said:

Likeliest areas are hottest and coldest. e.g.

Plenum heat often allows for hottest floor joists and other framing members. Pooling ceiling heat leads to truss expansion and center lift. 

Drafty areas or poorly insulated zones lead to rapid cooling. 

These kinds of areas lead to the most change. Cracks are far more common than creaks. 

Sounds are coming from the center of the house with conditioned space both above and below. Defiantly not cracks though, i doubt it could crack every night like this with out something majorly bad happening.

[Tpt life]

Check for truss lift if it is central and not HVAC. 

[wdwerker]

Air nails wouldn't help at all. Stab the carpet with a fat awl, (not an ice pick !) wiggle it around to open up the carpet back. Then drive a trim head screw into the ply & joist with someone standing right next to it ( to apply weight & close any gap) . You drive trim head screws with a Square drive bit, either a #1 or #2 size.  One of those impact drivers and a impact rated dive bit would probably work best. 

But if it's not a floor creak that is all moot.  If you end up pulling carpet a stud finder will let you mark the joist locations. The good ones will tell you if metal or power is nearby. You can carve out the ply between the joists with a saber saw, pull the nails and use a multimaster with a scraper blade to cut any adhesive then a new chunk of ply can be cut to fit.  

Careful methodical investigation is the starting point. 

[pkinneb]

46 minutes ago, C Shaffer said:

Check for truss lift if it is central and not HVAC. 

Truss lift?

[Tpt life]

8 minutes ago, pkinneb said:

Truss lift?

Truss bottom members lift in the center of span under load and bottom spread expansion. This is a common winter issue. They should not be nailed down in the center, but tied down with ties that allow this. Drywall on the ceiling must Not be screwed within two feet of the center partition or the corner where wall meets ceiling will crack. This is one reason a high end builder may choose to not hang a ceiling from trusses. 

Edit...Roof trusses

[Tpt life]

I am sorry. I chased the logic badly. If the center partition wall is tied to the truss and it lifts seasonally, you can get some studs sliding up and down bottom toe nails. I was defending the question as what is truss lift. You were asking why truss lift could caused a “floor” creak. Am I making better sense now @pkinneb?

[pkinneb]

26 minutes ago, C Shaffer said:

I am sorry. I chased the logic badly. If the center partition wall is tied to the truss and it lifts seasonally, you can get some studs sliding up and down bottom toe nails. I was defending the question as what is truss lift. You were asking why truss lift could caused a “floor” creak. Am I making better sense now @pkinneb?

gotcha that makes sense my basement is not finished I'll have to check it out. Thanks for the info.

 

[pd711]

It's strange that it happens only when the furnace stops running. If it were something that's expanding and contracting from the heat/cool cycle you would hear it both while it was expanding (heating) and while it was contracting (cooling).

[Tom King]

I don't know a thing about trusses.   I never used one.

[wtnhighlander]

Since the house is multi-level, I assume some ductwork may run through the joists between floors? Perhaps a leaky duct is allowing some pressure build up, that moves the floor (or ceiling below) slowly enough that you don't hear the creak as it runs, but do hear it when the fan stops and pressure drops suddenly, letting the floor settle?

[Tom King]

That's a great theory!    I have used a stethoscope to narrow down where a noise is coming from exactly.   You wouldn't think that it would give you any indication of direction, but it does.  Then you go in that direction as it gets louder, until you isolate it exactly.  Everything else has to be quiet though, or the background noise will cancel out what you're listening for.  It's as good a chance as any that it's the sheathing sliding against a nail.

[Pondhockey]

1 hour ago, wtnhighlander said:

Since the house is multi-level, I assume some ductwork may run through the joists between floors? Perhaps a leaky duct is allowing some pressure build up, that moves the floor (or ceiling below) slowly enough that you don't hear the creak as it runs, but do hear it when the fan stops and pressure drops suddenly, letting the floor settle?

That is an interesting theory, and perhaps testable:  if the phenomenon is related to air pressure it might respond to open/close doors, vents and windows.

[edit:  I wonder if you can cause the sound by running the HVAC without heat (i.e the "fan" setting.)

re-edit: oh, yeah, you said that the AC does not cause the sound.  Oh well.]]

[Chestnut]

I was looking around last night and the other interesting thing is the HVAC system runs around the outside walls and doeesn't appear to be in the area that the sound is coming from. Which makes me wonder if it's just a coincidence that i hear it when the HVAC shuts off. I'm going to try and secure down the subfloor with some screws and see where that gets me.

Truss lift that is an interesting thing I've not yet heard of. I can't say if that is the problem or not.

10 hours ago, wtnhighlander said:

Since the house is multi-level, I assume some ductwork may run through the joists between floors? Perhaps a leaky duct is allowing some pressure build up, that moves the floor (or ceiling below) slowly enough that you don't hear the creak as it runs, but do hear it when the fan stops and pressure drops suddenly, letting the floor settle?

This is an interesting theory. When I replace the flooring in this room i'm going to have to explore the subfloor and see what is going on.

[Bankstick]

FWIW, when one contractor was building a house in the subdivision behind us, I watched two guys put down the sub flooring on the floor joists.  They would run a bead of an adhesive, drop the panel in place, and nail or screw it down with an air tool.

[Tom King]

I got called to find, and fix a squeak in a house once (not one that I built).  It ended up being the underlayment rubbing against a wall bottom plate.  It only happened when the floor was walked on though.  As the floor flexed, the underlayment plywood (this was back before they started using thicker sheathing/subfloor in one layer) would move, up and down, rubbing against the 2x4 plate, and was surprisingly loud.