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truss brackets making loud popping sounds

truss brackets making loud popping sounds


  #1  
Old 01-26-15, 08:48 PM
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truss brackets making loud popping sounds

We have a 20-year old frame house with forced air heating. This winter (and to a lesser extent last year), the ceilings/walls started making loud popping sounds. After removing some duct covers and some drywall, I've isolated the sound to the brackets that tie the roof trusses to the center walls. The pops are very loud, loud enough to wake us many times per night. The popping is loosely related to when the heat turns on & off, but the sound is not coming from ducts - the heating ducts are in the floor and the cold air "returns" down between wall studs (ductless). The popping is also very loud in the morning, apparently as the sun heats up the roof.

Apparently, the heating is causing the trusses to expand and contract. I've been stumped why these sounds just started happening recently. After reading another post in this forum (http://www.doityourself.com/forum/wa...g-walls.html#b), I realized that we had the roof shingles replaced 2 years ago. We previously had a light colored wood shingle roof, now we have a darker asphalt roof. I believe the new roof provides a better seal than the old roof. The new roof might explain the morning popping sounds, but it does not explain the popping sounds at night.

The "attic" where the noise occurs is not accessible. It is a short space (maybe 3' tall max) between our vaulted ceilings and the roof. I don't think this attic space is vented. There aren't any soffit vents, nor any vents on the side of the gable roof. I haven't been able to check whether there are any vents on top of the roof.

Is the lack of venting a construction error? Would adding vents help reduce the expansion/contraction sounds by cooling off the attic?

The current truss brackets are nailed in. I've considered replacing the noisy brackets and/or re-attaching them with screws or lag bolts to fasten them more securely. But, I wonder if this solution would just mask the symptoms without solving the underlying problem

There are also some newly developed, small cracks between nearby walls and ceilings, but no cracks at the joints that now make noise. These cracks might be related, but the foundation does not seem to be moving, or at least not more than a 1/16" or so.

Any explanations or suggestions for the best solution?

Thanks, dave
 
  #2  
Old 01-27-15, 03:03 AM
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The "attic" where the noise occurs is not accessible.
I've considered replacing the noisy brackets
Welcome to the forums! If A, then how B??? What type "brackets" are you talking about? Where are they located? Pictures would help us, since we can't see what you see. http://www.doityourself.com/forum/el...your-post.html

Adding ridge venting won't help if there is no soffit venting, and if the roof has insulation packed in with no airway from soffit to ridge, neither will help. Can you determine if there is an air way between the two?
 
  #3  
Old 01-27-15, 04:06 AM
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The brackets you are seeing are there to provide partitions attached to the trusses with a moveable joint.

There is a phenomenon known as "truss uplift" which you can investigate. Attaching a truss to a partition without the benefit of a "floating" connection can result in the cracks you are seeing at the ceiling/wall joint. In your case it may be that the fasteners used to hold the brackets were driven in too hard and are causing the cracking issue. It may be that the brackets, being too tightly installed, are trying to flex when the temperature changes occur in the attic and are causing the noise.

Your observation about the roof are also somewhat valid. As the shingles and underlying plywood and framing lumber heat and cool there could be some expansion/ contraction issues that can result in noises being generated.

Tightening up on the truss brackets is not really a good idea. You could create further drywall stresses as the bottom chord of the truss expands and lifts off the center wall. Try to review them and make sure they have the ability to provide a sliding motion for the upward movement of the truss chord. The nails should not be driven firm.
 
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Old 01-27-15, 10:20 AM
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I removed a small section of wallboard to partially expose one of noisy brackets. Here's a stock picture of the type of bracket. Name:  truss-bracket.jpg
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Size:  19.9 KB . I tried to upload a pic of my actual bracket, but the upload continually fails.

This bracket nails into both the wall header and the truss. I don't understand how this bracket is movable or floats. It seems quite rigid to me.

I'm not sure if the noise is coming from the bracket torquing against the nails or the the nails/bracket torquing against the wood.

Other than the new roof, any idea why this would suddenly start happening in a 20 year old house? I'm thinking the new/tighter roof has reduced the little bit of ventilation that previously occurred. Seem plausible?

thanks, dave
 
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Old 01-27-15, 10:40 AM
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To clarify one point, the trusses are only used across the rear half of the house. The front half of the house has a sloping ceiling constructed with 2x12's (no trusses).

The noise comes from where the end of the trusses mount to the center wall of the house. The trusses are nailed to that wall using brackets like those in my previous post.

dave
 
  #6  
Old 01-27-15, 10:57 AM
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Your venting does need to be reviewed to ensure it is handling moisture.

The bracket you pictured is not what should be there, it is a hurricane bracket intended to fasten the roof joists securely to the house below. What calvert was describing allows the truss to lift off of the walls, but other details related to trusses and drywall may have been overlooked as well. Link below.

http://www.buildingscience.com/docum...d-truss-uplift

Bud
 
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Old 01-27-15, 02:21 PM
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Dark colored roofing now absorbing more energy from morning sun than light color roof did? Then at night the warmth dissipates and whatever pops when expanding now "un-pops" because it's contracting?
 
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Old 01-28-15, 04:57 PM
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feedback & more info

Thanks everyone for the pointers and feedback.

I'm not that concerned about the visible drywall cracks. They're easy to fix. The popping/cracking sounds, however, wake us up frequently.

Researching the local building codes (metro Denver), I believe the hurricane ties are common here. We do get very high winds. We built a detached garage one year ago using different builder. He used the exact same ties. I know it was thoroughly inspected. The tie manufacturer's website also recommends using screws for a more secure attachment, so I might try that on the two ties that make the most noise.

I verified that there are two 12" roof vents on that roof (10' apart), but no gable or soffit vents. The insulation bats are laid on top of the ceiling. I can't see if there's additional insulation attached to the roof, but I assume there's none based on how the rest of house was insulated.

To marynurse, the pops happen frequently as the heat turns on and off during the night, then again in the morning as the roof heats up.

I'd appreciate hearing any other suggestions.

thanks, dave
 
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Old 01-28-15, 05:29 PM
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I was going to respond the other day but held back. I was trying to visualize a situation to where the end of a truss would bear on an interior wall. Trusses usually span exterior walls and do not require interior bearing walls, in fact you want to avoid that.
The hurricane ties are good, whether required or not. So it goes back to why are trusses bearing on the interior?
Also your new roof is much heavier than a shake roof.
My comments are not helpful but inviting some thought.

As far as ventilation. It sounds like you have scissor trusses and no soffit venting was provided.
I think Bud or someone can explain it better than me. You need soffit venting and dams at where insulation meets soffit.
 
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Old 01-28-15, 06:29 PM
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It's a complicated roof design. The front half of the roof consists of simple 2x12's slanted up on a 5/12 pitch to the center bearing wall, forming a slanted ceiling on the front interior.

The back half of the roof consists of trusses between the center bearing wall and the rear wall. The trusses extend the front 5/12 roofline up toward the back of the house, peaking about 8' behind the center bearing wall. The reason for the trusses are to create a vaulted ceiling in the center of the rear room. Make sense?

My biggest concern is whether the visible cracks and the new noises indicate some foundation or structural movement. I've tried to get a structural engineer out to look at it, but they're all too busy. I verified that the center wall is level, so it isn't moving much if at all.

I saw something in the building code that wood roofs have more inherent venting than asphalt roofs, not to mention different heat transfer. btw, the old roof was Woodruff (essentially treated masonite, now off the market), not shake.

With these responses and other blogs I've read, I'm getting more comfortable that these problems are most likely caused by the decreased venting and the increased expansion/contraction caused by the new roof, not more serious structural problems.

So, it seems that there is some truss uplift happening and the uplift is loosening the tie nails, causing the nails, ties, and wood to bind and creak. The noise is getting worse every week, so it seems that the nails are continuing to loosen.

I wonder whether just tightening down the ties will temporarily (or longer) solve the noise problem until I can get the venting checked and resolved.

thanks, dave
 
 

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