the roof and framing have been inspected twice and found to have been installed to code.

another question might be is this a material failure or is this a workmanship issue? either way how can a builder say its normal and want us to accept that kind of work? I get it, he doesn't want to pay to repair the defect. but if its been built to code and the materials didn't fail, then would that be considered poor workmanship?

he has proposed blocking, with us paying for the materials. if we go that route, how far apart should they be placed? i could see it taking hundreds of them.

"the roof and framing have been inspected twice and found to have been installed to code."

Who inspected the work and what is the building code? Where is the project located?

The roofing underlayment looks like an impermeable synthetic that would not allow the sheathing to dry if placed on it when it was wet. This is third rate construction no matter where it is located. Its time to put the blame where it belongs. The contractor should be begging you to let him install blocking for free.

This is LP's specification for roof sheathing:'

Meeting building code and passing inspection is the lowest possible standard. It is all is that is required to be met. You passed inspection. You don’t have a leg to stand on if the sheathing is installed correctly, I don’t see how Res is seeing vertical application in those pics. I seem to see horizontal application, especially in that other shot .

If you wanted a better standard than minimum building code to be met? That better standard and better visual result would have to have been planned for from the beginning. Written into the details on the plans. Who did the building plans? The builder? A drafter? You?

You have unanticipated consequences of meeting the lowest code required standard. That isn’t on the builder. People also end up with a single zone 13 SEER HVAC, 3 tab 15 year asphalt shingles, and R-13 in their walls. That’s the lowest standard too. The results are worse for actual living in the home. They just aren’t as visible. People focus on the pretty and visible when it’s the boring and invisible that is really the important things to pay attention too.

You didn’t know what you didn’t know. This just shows that lack of knowledge on the outside.

"Our contractor and his partner are engineers."

Its astounding to me that engineers would not have known that 7/16" OSB on 24" o.c. rafters was already at risk of causing telegraphed rafters and that installing the panels vertically would reduce the strength of the panels far below industry, manufacturer and building code standards and would be highly likely to cause telegraphed rafters. And all those mistakes in judgement were compounded by installing underlayment and shingles over wet sheathing. The contractor couldn't have done more to reduce the strength of the sheathing and cause rafter telegraphing.

You have asked for help but have not revealed where the project is located so we don't know the required design live load or what building code applies.

It is also not clear what the specifications were for the roof sheathing. The drawings you posted say nothing about the sheathing. Who selected the sheathing and was it approved by you or your agent? Frankly, I've only seen OSB used at its maximum span limit for tract/spec housing. I have always specified 5/8" OSB on 16" spacing and some contractors insist on using 3/4" OSB but I'm in the Northeast.

Who was responsible for designing the code controlled elements of the house? Are there framing plans? Who sized the rafters? Was that information not submitted with the building permit application?

Building inspectors do not have the authority to approve code violations and they make mistakes like anyone else. I can't say for sure the inspectors are wrong without knowing the applicable code but I strongly suspect it.

The quickest and surest way to improve your negotiating position in this matter is to answer questions.

Also of great importance is adding blocking to some panels to see if that will reduce the telegraphing and to test the moisture content of the roof sheathing to see if it has stopped deteriorating from exposure to rain.

If you've lost interest in this matter, tell me and I'll leave you alone.

Even the greenest carpenter knows APA floor and roof sheathing span ratings are based on the long panel dimension spanning across joists and rafters. It’s even marked on the panels.
That means that when the long dimension is parallel to the framing, the panels no longer qualify for an APA span rating.
I can’t imagine there is a building code that would allow the installation of structural panel sheathing that doesn’t comply with APA’s standards but I can imagine there are contractors and building inspectors who are uninformed or don’t care.

Its obvious from the photos that he OSB panels are covering only two rafter bays.

Maybe they are installed in a staggered pattern which I believe is the norm.

With 24" spacing on the rafters, panels staggered 48" would look like this.

PPF, you may be right since the perspective is skewed by the wide angle lens and the distance from the house is so great.. We don't really have much hard evidence of what happened here which is frustrating.

That would leave the most likely cause of the sagging sheathing the contractor's decision to not allow the sheathing to dry before installing the underlayment and shingles. And the short roof ridge suggests that there might not be adequate ventilation in the attic so I wonder if there's any evidence of high humidity in the attic like high sheathing moisture content or mold. We'll probably never know but I find it difficult to believe the fault lies with the OP rather than the contractor.

For everyone's sake I hope blocking can correct the sagging.

The OP’s pic is just a common issue in all the builder grade houses around here, in a very humid mixed temperature climate. As in neighborhood after neighborhood. It’s so common that no one even sees it anymore.

The fact no one stick frames anything, and that the code allows 1/2” on 24” placed skinny little trusses, and doesn’t require 3/4” is more the root issue. No builder is going to spend an extra $500 where they don’t have to.

People who care about the end results upgrade their specs from that if they do custom. Either 16” spacing, or 3/4” material. Or both, in some cases.

Hi, Vicki,

I'm sorry for your experience.

I can't infer from the photos whether the sheathing was installed with the long dimension perpendicular to the rafters (which appear to be stick framed, not trusses) but that is what the APA panel certification stamp specifies as RES notes.

The fact that your contractor and his partner are engineers isn't particularly relevant since they were hired as a contractor, not as professional engineers. Their obligation as a contractor is to construct your home substantially as per the approved plans and specifications. It appears that the construction meets code requirements, as evidenced by the fact that code compliance inspectors have certified it as such.

I infer from the information you provided that the plans were competitively bid. For a contractor to "win" a bid requires them to cost out the minimum quality materials, trade labor, and services that meet the requirements shown in the approved plans and specifications. Don't expect more than that for low bid price. In fact, competitive bidding is an invitation for the "winning" contractor to exploit any errors and omissions at your expense when you have no control over the upcharge to correct them. Caveat emptor.

thank you so much for all your kind advice. the osb is laid horizontally on the rafters. rafters are 2x6 and the longest span is 13 foot i think. the city inspector came out twice and said its all to code. the first batch of osb got very wet. the second batch didn't and it hasn't failed. I feel this is a workmanship issue. The site and the sub contractors should have had better supervision. So, how best to proceed? And what financial amount is this? To re-roof or give added support?

the house is in NW Arkansas. thanks again for the advice.

As I said earlier, we don’t know much about this project but I had assumed from the simplistic design sketches that the structural design and specifications had been provided by the contractor.

Some contractors believe that wet sheathing dries to the inside. I’m not sure that’s true for this roof design. Have you inspected the attic for signs of excessive moisture like mold.

It’s not clear how you measured the OSB deflection. Place a carpenter’s level across the bottom of 2 rafters and measure the distance from the level to the sheathing at each rafter and at the middle. Subtract the middle dimension from the others to get the deflection. Do this in a half dozen locations. Of course your contractor should be doing this work but if he's not willing find someone else. Keep careful records.
Nailing simple 2x blocking between the rafters might work but there would be no adjustment possible during and after installation other than shimming at the middle of the blocking which creates a point support rather than continuous support.
For an initial trial I would try adding a 1x2 cleat 8 ft long on the lower part of the rafters flush with the bottom and placing a 2x4 above the cleats between the rafters and then shimming the ends of the 2x4 until the sag is gone. That would allow you to raise the deck gradually and adjust the spacing of the 2x4’s. However, the roofing nails might be an issue so perhaps only one cleat could be installed and then the other after the 2x4's are in place.
From that experiment you might find an easier and cheaper method for the rest of the sagging sheathing.
Whatever the cost or who pays it, I would want to be certain the ripple in the roof would be gone before agreeing to the repair method.
Its much easier to settle a dispute when a method and cost of an acceptable solution is known to the parties.

Res 3d, I've read through the above post and cant get my head around the cleat you are talking about.

Our roof is obviously a hip roof. this is very common in our area. the architect that designed the plans told us that the builder normally hands the elevations to the framer and he designs and builds it. zip board was installed and taped and the decking was also installed by the framer.

would it be easier to just have him install another rafter in between each existing rafter?

I've read through the above post and cant get my head around the cleat you are talking about.

Something like this? In theory, a cleat could be installed along each rafter and 2x blocking installed resting on it to level the sheathing.

You did not respond to my now deleted question about the state of the house. Is insulation and drywall installed in the ceiling?

One problem is simply access to the underside of the roof.

And as RES mentioned, there are probably roofing nails poking through the sheathing.

drywall is installed but no insulation yet. we just got tile down. and the sheet rock finished. the roof is very open as its a hip roof.

would adding another rafter between each existing one be the easyer option? The attic is very open and they would only have to remove the rows of bracing that hold up the rafters to have enough room to slide the new rafter in. what option would be the stronger repair?

meeting with the builder in the morning. contemplating telling him if he does one of these repairs at his expense we will sign off on the roof work. i doubt he will do it.

just remembered the nails poking through the sheeting. might have to go the blocking route

Since you want the builder to correct this at his expense, I'd ask him how he intends to correct and give him the opportunity to do so in a small section of roof as a test.

You would then inspect and approve or not.

I would refrain from offering suggestions until you are ready to take ownership of the problem.

Adding rafters would be virtually impossible and they would deflect at mid span instead of lifting the sheathing.

Remember that these panels probably got excessively wet and slowly sagged over a long drying period so they might resist being lifted all at once. However, its also possible the damage was so extensive that the sheathing has lost its strength permanently and will bend easily.

I've decided that the blocking detail I suggested earlier would not have enough bearing on the continuous cleats so I've attached a method that uses joist hangers..

I suspect this method would only partially lift the panels and then it would be necessary to add shims a little at a time over several months.

Whatever method you use should be carefully tested first; you don't want to lift the sheathing off of the rafters.

[EDIT] If the builder finds the sheathing is soft and easily pushed up it might be possible to nail the blocking in place without using joist hangers.

PPF is right about avoiding ownership of the problem and asking the builder to test his solution but you need to find a satisfactory repair method ASAP. t's not unusual for builders to drag their feet and force owners to find a solution. Sometimes you just have to do what needs to be done.

I doubt you are going to get this resolved without "participating" in the cost.

I can't tell how much of the roof needs to be reinforced but if all of it does, and the blocking is every 2 ft I'm guessing there would need to be about 250 braces @ $2 each material cost which would be a total of about $500. If only half of the roof needs reinforcing the total would be about $250. You need to check the quantities and costs yourself.

The labor cost working from ladders on sloping rafters will be much greater than that.

So... I recommend that you offer to pay for joist hangers and 2x4's.

If the sheathing had been 5/8" or the rafters had been 16" o.c. or the sheathing had been zip system or Advantech, the wavy roof would not have happened but any of those options would have cost you much more than the material cost of blocking.

[EDIT] If the builder finds the sheathing is soft and easily pushed up it might be possible to nail the blocking in place without using joist hangers. Its a simple thing to test.

There are alternate ways to force the blocking tight to the sheathing if the sheathing is no longer stiff.

Seriously, something like that would come under the “pound sand” portion of the builder’s contract. You don’t get to ask for change orders post closing. Unless you are willing to pay for the services of a structural engineer that will say that it’s comlromised structurally? It’s just easier to deal with living with as is.

I've seen OSB take on a "set" after being wet and drying out. For this reason it needs to be protected from the weather before installation and immediately afterwards.

I'm skeptical that any effort to plane it out after the fact will be successful. I don't know if your attic is floored or not, but installing blocking using ladders inside the attic without subflooring in place is a recipe for an accident. Proceed with caution.

Installing rafters @ 24" o.c. and using 7/16" OSB is not a recipe for a quality roof, although it is the norm for production builders.

Good points. I’ve seen OSB lose it’s strength and become flexible probably because it’s wasn’t very strong to begin with. Only trying the blocking will tell.
I recommend paying for a subfloor in the attic for safety and storage.
I don’t see telegraphed rafters as acceptable construction regardless of the contract unless the owner asked for it. OSB doesn’t fail that dramatically without someone making a mistake.

I proposed the above blocking approach only because I was concerned about the stiffness of the sheathing and how best to lift it if it were very stiff. Its quite possible that 2x4 blocking can be toe-nailed in place and shims inserted between it and the sheathing. Someone needs to get into the attic and experiment. This could be a simple fix or it could be more complicated.

We really appreciate all the thoughts, opinions, and professional advice! This has all helped us consider options we did not before. Keep 'em coming!

Did you talk to the builder today? We need more information like is there mold in the attic or an attic subfloor or what kind of blocking would be needed to lift the sagging sheathing?

I am scheduled to meet with our builder this week. He is currently at a conference. I want to approach in a non confrontational way with facts in hand. I do NOT try to resolve an issue without first researching as thoroughly as possible. Weather the issue was material handling, workmanship, roofers, framers, it is ultimately the contractor's responsibility to supervise the build. I doubt there is mold of any kind (frame and roof mid May 2019), there is an attic sub floor. I have no way personally of climbing up in there and taking photos, but I can have someone do that. We began mentioning the issue in May.

If the OSB sheathing was throughly soaked before an impermeable synthetic underlayment was installed over it, the sheathing could only have dried into the attic space which would have raised the humidity level.

If the attic ventilation was limited to a ridge vent and perimeter eave vents there would have been little air movement in the attic (the ridge vent is very short for the size of the attic) and if there was no mechanical ventilation provided to speed the drying, the sheathing would have dried very slowly.

In this situation, the conditions needed for mold are wood, darkness, warmth and moisture, therefore, I would not assume the attic has no mold growth in it. Its time to take a look.

The attic is required to have an access hatch so all you need is a ladder unless an optional pull-down access ladder has already been installed. Take photos of everything.

the attic floor is limited to the first 24' of the 80' long home. its over the garage. We don't have a ridge vent only twelve of the metal <passive?> vents. I doubt we have enough ventilation because when standing under the attic access in the garage the heat pushes out to the floor below the access hole. I've recently spoken with the builder and he said the twelve vents are rated to be enough for a home with 100 less sq ft then what we have. he quoted me $150 to add 4 more vents. He did offer to pay of the labor to block if we paid for the materials.

I'm puzzled.

If all but 24 ft of the 80 ft length of the house has no attic floor, does that mean it has a 56 ft long cathedral ceiling in the rest of the house? That would be difficult to build with 2x6 rafters and would require a serious ridge beam and posts or bracing/ties. Or do you mean there's an attic floor but no subflooring on it?

You said "rafters are 2x6 and the longest span is 13 foot i think.". But the photos show about 20 rafter bays which would be about 40 ft. with a rafter span of 20 ft. which is more than a 2x6 rafter could span without intermediate supports.

Its a very puzzling building. Are there no dimensioned construction drawings for it? How did you and the builder know what was going to be built and how was it possible to get a building permit?

Thanks PPF. If the building width is 42-0 the rafter length including the eave overhang would be about 26-6 and the total horizontal rafter span would be about 20-8 and if braced at the mid point the rafter could be sized for a span of 10-6. (SPF #2 can span 11-9). If the building is 40-0 wide the dimensions are reduced a foot or so.

That's a very big roof. If blocking was placed in every rafter bay at 24" o.c. there would be about 800 pieces. Reduce that number by the areas that don't need blocking or can have blocking spaced farther apart. I would assume the worst case.

If the contractor is willing to do a thorough job of blocking, it seems wise to agree to pay for the materials but I would want to see a test of the blocking first.

No ridge vent? Whirlibirds? I’m supposing no soffit vents either. Cheesy basically undersized roof framing. Geez. This isn’t 1979. Who designed and specified this $1.98 hot mess. Bet it came with granite counters though.

Before the mud slinging begins and I say goodbye to this thread, I'd like to point out that although its not worth the hassle and expense to go to court, if that occurred, the contractor would not be able to use building code compliance as a defense because engineers, like architects, are held to a much higher standard of knowledge and judgement for construction matters than others in a court of law.

I can think of no defense for the severe sheathing damage. Weather records will show how much it rained and there will be witnesses to the fact that the roofer allowed no time for the sheathing to dry before installing a vapor impermeable synthetic (plastic) underlayment ignoring manufacturers' recommendations and effectively guaranteeing a reduction in the structural rigidity of the sheathing.

I'm not a lawyer but I've been on jury duty 6 times and the first time was for a month. So, unless the contract calls for some other kind of dispute resolution, the contractor would be foolish to not negotiate a settlement while he can.

I think the OP would be well served to contact technical support at the manufacturer of the OSB and send them plans and photos. There's a good chance they've seen something similar before and can assist with diagnosing the problem and helping to think through the various possible ways to mitigate it.

Good advice but this is all LP says about wet OSB sheathing in their product specifications that include installation instructions:

Cover roof sheathing as soon as possible with roofing felt or shingle underlayment for protection against excessive moisture prior to roofing. If any edge swelling occurs prior to roof underlay- ment installation, all raised joints should be sanded flat. Allow sheathing to adjust to humidity and moisture conditions before shingle installation.

Of course, the contractor should already have contacted the manufacturer and supplier. Its his responsibility to find a solution.

I'm not sure there's a reasonable fix for the problem short of tearing off the affected panels and replacing them. A call to the panel manufacturer might be a short cut to testing out alternatives if that's the case.

From what I gather, the builder doesn't see this as anything but an aesthetic issue, so I'm not confident he's done anything.

It appears the builder doesn't want anything to do with remedial work, despite the way in which wet materials were apparently installed,

Is it it time for the OP to consider alternative means to have a properly installed roof?

While I would hope the builder would take a more active role in identifying the root cause of the problem, I don't think we have sufficient evidence to hang him--at least not without some company. As Green Designs noted, telegraphing of trusses and sagging of OSB roof sheathing are fairly common in tract-built homes. I've observed the same. It's what you get for pushing everything right to the limit in an effort to wring out costs. Unless the project is a design/build project, the rafter spacing and OSB thickness were specified by the designer, not the builder. The project was competitively bid, so please don't expect the builder--engineer trained or otherwise--to exceed design specifications. You don't get to "win" bids that way. And don't expect every engineer to be an expert in construction. Electrical engineers, industrial engineers, software engineers and the like won't know any more about residential construction than your average homeowner.

RES and Green Designs both raised questions about attic venting. I don't think they were answered in a way that we can conclude the venting is adequate nor can we conclude is was at the time the sheathing was installed. Consider that the OP's photo shows installation of OSB panels on the opposite side of the roof from the problem area. If the problem area was installed last, and there was inadequate venting of the attic at the time (potentially none at the time the sheathing and underlayment were installed) those factors may have resulted in an objectionable amount of sagging compared with what would have been the case with the same wet OSB and better ventilation.

Regarding venting, we have 12 vents and are right at the number needed for the attic. If we add 100 sq ft to calculate, it would be 13 vents. Not grossly undersized but right on the line. They are evenly spaced metal vents so adding another will make it uneven. Contractor is checking on insulation cost to compare to.

Has anyone been in the attic to check for conditions there...?

Ridge vents/soffit vents have been standard since some time in the 80’s. There is no one knowledgeable in the construction world who would NOT do them. https://www.buildingscience.com/documents/published-articles/pa-crash-course-in-roof-venting/view

https://www.buildingscience.com/documents/digests/bsd-102-understanding-attic-ventilation

https://www.owenscorning.com/NetworkShare/Roofing/10013807-Ventilation-Training-Manual.pdf

Hi, Vicki,

I don't see any of the type of vents you described in the photo of the wavy roof. At what point during construction were they installed?

Most likely some of the rafters weren't crowned that could also be one of the reasons why you would notice depressions, and depending on the time of day you would see the shadowing effect because of that.

As the vents goes, I'm sure they installed roof vents on the back of the house since there is no ridge vent at the top ridge, if not as Charles said, they would have to be installed.

Going to post pictures specific to roof construction. The framing

Vents are installed on the north facing side of the roof

The OSB board

half the OSB was legible (red edge on board), the other half (blue edge on board) were absolutely NOT legible

Were the vents shown installed when the shingles were installed or when the roof sheathing was installed? My concern is that the conditions in a closed up, unvented attic on a hot day with moisture in the OSB were probably sauna like and may have contributed to the problem.

Also, please confirm there is continuous soffit vent installed at the eaves.