# Buckled roof sheathing - what next?



## roofermann (Nov 18, 2013)

Pics please.


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## joecaption (Nov 30, 2011)

Is this your first house?
There's suppose to be a gap between the sheets to allow for expansion.
The gap between the sheets along the long length was suppose to have in most cases H clips between the rafters or trusses to keep it from sagging.
http://www.nachi.org/h-clips.htm
Very common and not an issue in most cause to miss a few nails when nailing from above.
Legal or not that vent needs to run out the roof not the soffit. Once your venting is fixed that hot moist air is going to just get sucked back into the attic if it's left in the soffit.
May now need to add blocking to push the plywood back up, it's not going to straighten it's self out.


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## jack45870 (Sep 17, 2014)

That was a great story, But without a pic i can't say anything


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## Patriot_fan (Sep 30, 2014)

roofermann said:


> Pics please.











Test - pic of insulation blocks that were covering two soffits


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## Patriot_fan (Sep 30, 2014)

roofermann said:


> Pics please.



























1st pic is what the seam between two pieces of sheathing should look like - nail-width gap

2nd pic - you can barely make out the seam running horizontally along the middle of the pic - no gap at all between two pieces of sheathing

3rd pic - I have my fingertip resting on the ledge formed by a warped piece of sheathing - prob about 1/2" warpage from where the sheathing should be.....at first pass, I've seen this in several spots on the roof deck. Not sure how bad this is on a scale of 1-10, and thus not sure if I should go through the pain of removing shingles above the warped spots and replacing the sheathing.......and it might be more of a can of worms in that to get the proper spacing I may have to remove good sheathing around the bad and re-align the whole lot, which could turn into a big job - or do you alternatively just custom cut the new piece of plywood down to the correct size so the surrounding sheathing can stay in place?

Edit - 3rd pic should be rotated 90 deg clockwise - the ledge seen here is along the horizontal seam between two pieces of sheathing.


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## Patriot_fan (Sep 30, 2014)

1st pic - another spot with warped sheathing (should be rotated 90 deg clockwise)

2nd pic - (also should be rotated 90 deg clockwise) might be hard to make out, but this is the typical layout for running bathroom fan exhaust ducting (coming from the left, on top of the blown-in insulation, and terminating at the soffit). I guess this all needs to be remedied, with the fan exhaust running out through an external vertical vent pipe (going up through the sheathing). Figure a decent home builder would have done this to begin with - as is, seems completely half-assed to me (but meets IL building code according to the guy who inspected the house before we bought it). Speaking of inspectors, how did the inspector not catch the warped sheathing (which I can see very easily, now that I now what to look for) when he was poking around the attic and saw the extensive mold?


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## Patriot_fan (Sep 30, 2014)

joecaption said:


> Is this your first house?
> There's suppose to be a gap between the sheets to allow for expansion.
> The gap between the sheets along the long length was suppose to have in most cases H clips between the rafters or trusses to keep it from sagging.
> http://www.nachi.org/h-clips.htm
> ...


Yes, it's my first house. I can't see H clips anywhere between the sheathing.

How does adding blocking solve the problem - the fact remains that there will still not be an adequate gap between the sheathing, correct? Wondering if I can live with this problem, or do I need to go to the extreme of taking the bad sheathing out and re-doing it - not cheap I reckon.....still pissed that my home inspector didn't catch this.


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## Windows on Wash (Aug 30, 2011)

H-clips are really designed to help with span and plywood spacing.

If the decking is of a proper thickness, spaced properly, and the span manageable, they are not required.

The issue with your roof is still moisture and venting. Maybe not as acute as the case of the bath fan but the I don't see any of the details on the roof venting.

What I do see is insulation in the soffit box. 

That attic needs air sealing and insulation and you need to look critically at the venting and do so before winter sets in.


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## Patriot_fan (Sep 30, 2014)

Windows on Wash said:


> H-clips are really designed to help with span and plywood spacing.
> 
> If the decking is of a proper thickness, spaced properly, and the span manageable, they are not required.
> 
> ...


There are three bathroom fans that all lead to soffit vents + a master bedroom walk-in closet exhaust fan that also leads to a soffit vent. Also, in my first pic above (showing the insulation blocks that were blocking two soffits), you can see a clothes dryer exhaust duct that is run out through the roof - it looks to me like that was a post-construction modification, so perhaps the previous owners had the clothes dryer in the master bedroom walk-in closet also exhausting to a soffit vent for some amount of time - who knows. 

My point is, some previous, and perhaps significant, fan exhausting to the attic, combined with insulation blocking some soffit vents could be the culprit here. I'll need to rectify the fan exhaust and clear all soffits.

A quick look shows that with my 2,040 sq ft attic, I have 15 soffits (2.9 sq ft net free area) and 11 8" round ridge vents (3.8 sq ft net free area)....so 6.7 sq ft total net free area and meeting 1/300 code - although a bit "top-heavy" on the upper-lower venting balance, with the ridge vents accounting for 58% of the total net free area, and I think it's recommended that the ridge vents should account for 40-50% of the total net free area.

So I'll fix the ventilation issues - still wondering what to do about the warped sheathing......

Why do you say that the attic needs air sealing and insulation? Appreciate your comments, and thx for your input thus far!


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## Windows on Wash (Aug 30, 2011)

Fans have to go through the gable end walls or through the roof. Sooner than later.

Dumping them into the soffit does not work.


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## joecaption (Nov 30, 2011)

How thick is that sheathing?
Adding the suggested blocking will lift the plywood back in place and stop it from sagging again.
Cut them so they fit snug, tap one side up tight to the plywood and nail that side then tap the other side up and nail it. Works like a lever to give you more lifting power.
Makes 0 since to remove shingles just to make cuts in that sheathing so there will be a gap. 
Wait until the shingles are replaced.
Is the underside of that sheathing and the rafters really white like they look in those pictures?
Makes me wonder why someone would go to all that trouble unless there was mold they where trying to cover up.
All attics need air sealing, if not your going to have moist hot air from inside the home and HVAC loss into the attic.
It's just using expanding foam to seal up any wiring, plumbing, ceiling fixtures, holes in the top plates and ceiling.


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## Patriot_fan (Sep 30, 2014)

joecaption said:


> How thick is that sheathing?
> Adding the suggested blocking will lift the plywood back in place and stop it from sagging again.
> Cut them so they fit snug, tap one side up tight to the plywood and nail that side then tap the other side up and nail it. Works like a lever to give you more lifting power.
> Makes 0 since to remove shingles just to make cuts in that sheathing so there will be a gap.
> ...


Thx for the response Joe.

Don't know how thick the sheathing is - I'll check later today.

Yes the sheathing & rafters are white - coating was added as part of the mold remediation process prior to our purchase of the house.

Thx for the clarity on the need for air sealing the attic. 

You also mentioned that I need insulation - what did you see in my pics that led you to that conclusion?


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## Patriot_fan (Sep 30, 2014)

Windows on Wash said:


> Fans have to go through the gable end walls or through the roof. Sooner than later.
> 
> Dumping them into the soffit does not work.


Roger that!


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## fortunerestore (Mar 6, 2014)

If you look forward to insulate, be sure that it’s done real carefully. If moisture gets into the insulation it may not work and you may end up with disturbing bills.


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