We have new all ICF house with a hip roof, wood trusses 2' oc with 48' span and a sheet metal roof. The attic has 2" of spray foam and 18-20" of blown in cellulose. It has been very cold here in MN about once a week we hear a loud noise that sounds like it is coming from the roof/attic but hard to pin-point, since it is sudden and short. It is a dull thud, like when snow slid off the roof last winter, but that is not the case. We heard it about once a week when it was bitterly cold, but yesterday it warmed to 32 and humid and the noise caused us to jump out of bed last night. The ceiling drywall is cracking badly and the truss lift issue was brought up but the cracking is in the field of the ceiling, not where the ceiling meets walls. A drywall guy thought the cracking has to do with large span of the trusses

What type of metal roof do you have? How is it attached to the roof framing? Are fasteners visible on the exterior side of the metal roofing? External fasteners means the metal roofing is rigidly attached to the wood framing and doesn't allow for movement of the metal due to thermal expansion/contraction. This can put a strain on the underlying structure, especially with long runs of metal like you would have with 48' span trusses.

Do your roof trusses have purlins running perpendicular on top under the metal or was the roof solidly decked with plywood/osb prior to installation of the metal roof?

Also, with that long of a span, unless you have a really low roof pitch, I would assume your trusses are two pieces - a bottom section and a top section. Also, was your hip portion of the roof stick built or do the roof trusses step down under the hip section? With all of these possible different truss sections being attached together in the field, there is a possibility of differential movement, especially if they were just attached to each other with just a few toe nails from an air gun here and there.

Noise moves around on an ICF house and is often hard to pin point.

List of suspects.

Metal roofing contracting or expanding around fasteners or sheet to sheet.

Some siding will do the same.

Very small chance that it is foam to truss or drywall.

In our case, metal clad wood windows that pop as the metal heats and cools but uses the ICF as an acoustic board.

Plumbing pipes that don't have the proper expansion joints at the proper locations.

Top chord of truss is getting shorter as it cools and dries and may de moving very slightly on the top of the ICF. The truss holds up till enough pressure is exerted and then moves that little bit but it is enough to make a big noise of very short duration. The steeper the pitch and the shorter the span, the more of an issue you will have with drywall. The brace chords and the top chord are both subjected to the climate of the outside while the bottom chord is near room temperature as it is hidden in the insulation. As the exposed wood cools it shrinks and lifts up the bottom chord. In sever cases here in Calgary we have seen the bottom truss chord lift an inch and one half off the center walls. Some of the noise may be nail release.

We don't usually see the drywall cracking mid plane as a result of truss movement. What is the relative humidity of the house? It is important to keep fresh air moving through an ICF house for the first year or two as the ICF gives up its moisture very slowly. It is even more important if the contractor did not use water reducer in the concrete mix as it means there will be more moisture to work its way out of the foam. It is possible that the drywall was moist going in or gained moisture due to high humidity levels and is now drying out. Do you have a standard force air system. Have the cracks started late in the year? Is there a poly vapour barrier over the ceiling drywall? What was the building time frame and temperatures?

Most all these noises get less and less each cycle the building goes through so in a year or two you won't notice them anymore.

I am currently in a wood frame house and it POPS and makes noises at night when it gets cold or if there are great temperature swings. The popping and splitting sounds come from the wood roof trusses. It's 100% normal. Wood is always moving, growing, shrinking, swelling, etc. it gets wet, dries, cools, heats-up, etc.

Wood roof trusses are made from young trees which contain A LOT of moisture. As they dry out, the will move around and make noises in the process.

The 4/12 pitch roof consists of 1/2" OSB sheathing under an exposed fastener sheet metal roof, 29 gauge pole barn metal. 4' eves.The house is 48' square so no ridge with the hip roof, comes to a point. The sheet metal starts at 30' and goes down from there. No known problems with the roof. There is two girder trusses 8-10 from the walls, all lateral and diagonal bracing was done to or beyond truss companies specs, which does not include bottom cord bracing.
The 2" of polyurathene spray foam is the vapor barrier, no poly.
The cracks in the ceiling are mostly in the seams but not all, evenly spread.
The noise is sudden and loud, two nights ago, when we last heard it the temp had increased 30-40 degrees (to about 25) in 24 hours. This is the third winter and have heard noises 6-10 before this winter, we have had the coldest weather in 20 years.

Almost for sure the popping is from the roof to wall connections. Most likely the girders sliding as little as 1/8 of an inch back and forth on the concrete/sill plate. As the truss floor lifts in the middle the material has to come from somewhere. In a stick framed house, the walls would just lean in and out to accommodate the shrink and growth of the bottom chord but the ICF does not have that give especially within eight feet of the corner. So as the top chords/knee braces change length they pull and push on the bottom chord forcing the heel of the truss to move just a wee bit. This is not a nice even pull but a sudden release as tension over comes friction. The sound is then amplified through the concrete.

As to the cracking, I'm wondering if anyone else that has used spray foam has experienced this??
When did the cracking start?
Is it getting worse?

Maybe it is time that we start attaching trusses to concrete walls so that the trusses can slide - like bridge spans on pillars.  Also similar to using hidden clips to attach standing seam roofs.  Just saying.

Alton - I was thinking along the lines of a teflon or hd plastic bearing plate.

The only place I have it on my own house is at the girder truss for the turret which is 12/12 and about a 20' span. This is our thrid year and I have not heard it as yet this year. Maybe just not home when it happens.

Have you heard of any issues with spray foam that could effect the drywall?

Spray foam has extensive use in my area.  I have not heard of any problems that affected drywall.  My guess is that closed cell spray foam on a drywall ceiling would allow the drywall to carry more load without sagging or cracking.

I have not had any problems with roof trusses being clear spanned on truss girders.

I have read that exposed fasteners on metal roofs is a problem spot for noises/movement. Concealed fasteners is supposedly the better route to go.

A wood home does have movement and a wood frame roof/truss are no different. The "ductility" of wood frame is something that is going on here. The wood is expanding and contracting but the concrete wall is not. Therefore something is going to "give" and in this case as mentioned, there is sudden movement and the resulting noise.

Our trusses sit directly on the concrete walls and are fastened with Simpson Strongtie LTA2. Trusses were set in the winter. Cant really say when the drywall cracking started, but I think right away and has just kept getting worse.

I’ve read where it is recommend that in order to keep your ceiling from cracking due to contraction of truss members that you should only fasten down the truss on one side of the house and let the other side float. While this makes some sense in the effort to keep your ceiling from cracking, it doesn’t do a whole lot to keep you roof on the house during high winds. It would be nice if there was a fastener that would hold the truss down while letting it slide in and out. Seems like it would be a simple design.

Posted By MSG79 on 14 Jan 2014 10:23 AM
I’ve read where it is recommend that in order to keep your ceiling from cracking due to contraction of truss members that you should only fasten down the truss on one side of the house and let the other side float. While this makes some sense in the effort to keep your ceiling from cracking, it doesn’t do a whole lot to keep you roof on the house during high winds. It would be nice if there was a fastener that would hold the truss down while letting it slide in and out. Seems like it would be a simple design.

I would NOT advise doing that. First, it wouldn't pass code. Second, in a strong wind the roof would want to lift off and fly away like a kite.

The problem is always the ductility of wood. By nature it wants to and will move. In an all wood frame home, the walls and roof move and no real issues come up. In a concrete wall and wood roof, you will have problems because concrete does not and will not move. Whenever you have 2 dissimilar materials, there is always some type of expansion/contraction issue.

••• only fasten down the truss on one side•••

Yeah, I don't think so. Structural integrity always comes first. It is not usually the bottom chord that shrinks anyway, it just bows up as the web members shrink which shorten the straight line distance heel to heel. In any case, OP indicates that the trusses are attached with Simpson LTA2s which are a side mount type attachment. This would allow enough movement without tearing nails free. If a piece of sheet metal had been slipped under the truss, it would have decoupled the wood from the concrete and eliminated the noise. (hindsight is 20-20).

Exposed fasteners do not create noise. There is nothing for them to interact with as they are in a tight self pierced hole. Also this type of steel roofing does not cause noise. If it did it would be a sharp noise as opposed to a dull one. That said, it should not be used on homes or other places where water tight is required. If the side laps are butyl taped, that would eliminate the normal side lap leakage but over a period of a few years, the expansion and contraction of the 30' sheets will either tear out the screws or elongate the hole in the sheet metal to the point that they will leak.

Since cottage style roofs have been done with trusses and flat drywall ceilings for several decades with no harm done, I would tend to look to what has changed.
Is the metal roofing leaking? This should be visible as water stains on the underside of the osb sheathing.

Does the spray foam form all or part of the problem?
The spray foam would bond the drywall and bottom chord of the truss into one monolithic unit. How does this effect the drywall? Is the foam cracking as well as the drywall? I don't see how the drywall would crack by itself if evenly adhered to the foam so I think this might be the case. If both are cracking, why? Either the foam is shrinking or the bottom truss chord is expanding to cause the gaps in the drywall.
We have heard of cases where spray foam when not properly applied (usually improper temperature of the agents) will shrink. Could it be pulling the drywall with it? (Trusses where mounted in the winter. What was the air temperature when the foam was sprayed?)

Is it possible that due to no vapour barrier between the wood truss chord and the room climate, the moisture is being drawn into the truss chord? This should not happen as OP indicates 18 to 20" of cellulose over the foam so there is no way that the wood could be at dew point. Is there another way that moisture is getting into the bottom truss chord? Water running down the webs and sneaking past the foam? Possible but that should manifest itself as water staining on the drywall.

I would into the attic to check things. If it is again quite cold, look for frost crystals adhering to the trusses and sheathing indicating high moisture levels. Move the cellulose aside in the area of a drywall crack and see if the foam is cracked as well. Also check for high moisture or saturation in the lower cellulose. If the foam is cracked as well as the drywall, it may be the foam was not properly installed. In any case there would no longer be an air or vapour barrier as the cracks are all the way through so this needs to be addressed.

If there is no visible cracking of the foam, expose a portion of the bottom truss chord and check it with a moisture meter.

Anyone have any other thoughts on this??

In our area, I'm just over 200 miles from the ocean, they changed the code about 12 yrs ago that all trusses had to be tied down with hurricane straps. Would this prevent this from happening?

Posted By robinnc on 14 Jan 2014 10:19 PM
In our area, I'm just over 200 miles from the ocean, they changed the code about 12 yrs ago that all trusses had to be tied down with hurricane straps. Would this prevent this from happening?

I believe hurricane straps just create a "continuous load path" from the trusses, to the wall top plate, down the wall to the bottom sill plate, and finally to the foundation. They help prevent wind uplift with the trusses but they don't stop expansion of the trusses due to thermal cycles.

My roof trusses pop every night around 10PM - 11PM, as that is when the greatest temperature differentials are happening. It's just the nature of wood.

The husband was just in the attic a couple weeks ago, to wire something, and there was no sign of moisture, condensation of roof leaks. The spray foam was done in November 2011, so it was probably freezing at night.

Thanks for all this help.