# Drywall Cracking Under Snow Load



## Gary in WA (Mar 11, 2009)

If the cracks are on dormer wall/roof, then yes- you need rafter ties (or a ridge beam) on top the wall plates- they could also work as ceiling joists for the drywall; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_par022.htm?bu2=undefined

Gary
PS. Welcome to the forums!


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## bheemsoth (Oct 7, 2012)

Gary in WA said:


> If the cracks are on dormer wall/roof, then yes- you need rafter ties (or a ridge beam) on top the wall plates- they could also work as ceiling joists for the drywall; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_par022.htm?bu2=undefined
> 
> Gary
> PS. Welcome to the forums!


Thanks for the quick reply! One question.. The existing ceiling joists span the entire way front to back 24" o.c.. Wouldn't these be serving the same role as rafter ties?


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## bheemsoth (Oct 7, 2012)

"Dormer" wasn't really the correct term. Sloped ceiling is really what I'm referring to.


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## Gary in WA (Mar 11, 2009)

I mentioned dormer ceiling.... if this is on the house, your attic floor (ceiling joists) would tie it all together. I understood the picture was of a dormer sloped ceiling- without level ceiling joists- just collar ties (in upper 1/3) above. More pictures would clear it up, please....

Gary


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## bheemsoth (Oct 7, 2012)

Gary in WA said:


> I mentioned dormer ceiling.... if this is on the house, your attic floor (ceiling joists) would tie it all together. I understood the picture was of a dormer sloped ceiling- without level ceiling joists- just collar ties (in upper 1/3) above. More pictures would clear it up, please....
> 
> Gary


Gary,

I'm sorry for the confusion. There are no collar ties - just 2x6 ceiling joists that are nailed to each of the rafters 24" oc. At first I was thinking that adding some collar ties may help, but that doesn't seem likely to help with the forces of the snow load. 

From a design perspective everything seems stout based on my limited knowledge and the research I've done. This is all pretty perplexing.


Here are some more pictures I took of the attic just now: 











This picture shows the joists (mostly buried in insulation) along with the rafters. The rafters are nailed to the joists where they intersect.


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## oh'mike (Sep 18, 2009)

Wow--those are some rather light duty rafters---are they 2x4s?


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## bheemsoth (Oct 7, 2012)

oh'mike said:


> Wow--those are some rather light duty rafters---are they 2x4s?


They are 2x6. I think the perspective of me standing on a ladder in the hatchway skewed the picture.


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## oh'mike (Sep 18, 2009)

Still rather weak---typically there are collar ties (cross bracing ) between the rafters --those add stiffness and reduce flex----might be worth adding them---


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## bheemsoth (Oct 7, 2012)

oh'mike said:


> Still rather weak---typically there are collar ties (cross bracing ) between the rafters --those add stiffness and reduce flex----might be worth adding them---


Thanks Mike - that's one of the options I was considering, but I wasn't sure since I'd read that they mostly help with wind uplift more than anything. It would be a cheap fix though on my part. 

How high do you think I should mount them on the rafters, and what size lumber would you recommend?

Gary - what do you think?


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## oh'mike (Sep 18, 2009)

I'd use 2x6---about 1/3 of the way down from the ridge.

Gary will have the correct answer on placement.

As to the drywall lifting at the ceiling/wall junction---the drywall was not installed properly---the ceiling drywall rests and floats on top of the wall sheets---no screws are used withing 16 to 24 inches of the wall---

Thus the framing can expand and contract without tearing the paper corners.

To late to fix it now---How do you like crown molding?


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## bheemsoth (Oct 7, 2012)

oh'mike said:


> I'd use 2x6---about 1/3 of the way down from the ridge.
> 
> Gary will have the correct answer on placement.
> 
> ...


Yeah, crown is going to be an option probably. I'll have to figure out a way to make it look right with the dormer ceiling. 

I was also considering taking out the drywall tape in those joints now (8 of them) and replacing it with a product like this - http://trim-tex.com/product_catalog.php?cat_display=showproduct&id=263


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## oh'mike (Sep 18, 2009)

I've never tried that one----I do use 'Straight Flex' on ceiling/wall junctions---


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## SPS-1 (Oct 21, 2008)

They used that flexible bead on the angled joints on my ceiling when I had it cathedralled. I can say that I see no cracks. But I don't think it is intended for the kind of movement you are seeing. 
Are the attic pics directly above the problem areas? The living area pics show a sloped ceiling. The attic pics look like a horizontal floor.


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## bheemsoth (Oct 7, 2012)

SPS-1 said:


> They used that flexible bead on the angled joints on my ceiling when I had it cathedralled. I can say that I see no cracks. But I don't think it is intended for the kind of movement you are seeing.
> Are the attic pics directly above the problem areas? The living area pics show a sloped ceiling. The attic pics look like a horizontal floor.


The attic is directly above the area seeing the issue. The design is somewhat unique. There is a sloped ceiling for a couple of feet in from the front and back walls of the house, then a standard ceiling for the remainder of the span - sort of like /=====\

The ceiling rafters attach to the wall plate, then intersect the ceiling joists about 2ft into their span. Near this intersection is where we're seeing the cracking.


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## bheemsoth (Oct 7, 2012)

Gary or others - any input on the collar tie installation height to best help with these issues?


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## oh'mike (Sep 18, 2009)

You need an answer from a framer---I suggest you start a framing thread---the carpenters seldom look into this forum---Mike----


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## Daniel Holzman (Mar 10, 2009)

Collar ties are normally installed 1/3 of the way down from the peak to the joist, as Oh Mike previously indicated. The purpose of collar ties is to equalize uplift pressure on the roof during high wind events, so they are not likely to improve your particular problem, but they are supposed to be installed, and they won't hurt anything.


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## Gary in WA (Mar 11, 2009)

Sounds a lot like this, from David Utterback; "
Rafter ties do not have to be at ceiling height to be effective, but they must not be placed any higher than the lower third of the roof pitch. In other words: Measure vertically from the outside wall's top plate to the bottom of the ridge, and place the rafter ties within the lower third of that measurement. Once they get above that point, they lose their most effective leverage.
I've seen builders compound their mistakes when they try to use rafter ties as ceiling joists in semivaulted ceilings. For maximum headroom or aesthetic balance, they place the rafter ties halfway up the roof pitch, near the center of the rafter span where they're too high to be an effective tie. Applying the insulation and the drywall greatly increases the load on the rafters at their most critical point: midspan (what engineers call the maximum bending moment). This added load can cause the rafters to sag, pulling the ridge down and also pushing the exterior walls outward." From; http://myconco.com/ComEngProb.html


I doubt they used any bolts on the rafter/joist connection*; pp.7*; https://docs.google.com/viewer?a=v&q=cacheghGXrd_ZtgJ:www.apexhomeinspections.biz/articles/framing%2520guidelines.pdf+roof+framing+guidelines&hl=en&gl=us&pid=bl&srcid=ADGEESgq1FlmNMbRKrtrO0p2QA17Hx-vCQ5MWxH_tnethCNeGJjhSa1gfolZvHrLTEoQUzRxVpUMvQhX-XX41JohKIPHnbdld7JETpg-bUfoErW0goKFZAOfCRxiJsn4u2QtaiJPvFTv&sig=AHIEtbTS7d4A8WuCudIWWvZygC-vGi-JoA


As in Fig. 10A, but the joist are rafter ties; https://docs.google.com/viewer?a=v&...FJ0itT&sig=AHIEtbRtV80-3uHD-E_6RMyCq7zQ737mAg


They may have put them too high, measure the height of the ceiling to top of a window inside; go outside and measure the window to top of wall or soffit block- if soffit isn't dropped.


Gary
PS. My post 5 on collar ties....


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## eandjsdad (Dec 22, 2013)

Retaping isn't going to help. The drywall should have been floated both sides of those cracks you're seeing to minimize cracking, but some framing issue is behind it all.


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