# Truss uplift



## arnoldat30 (Feb 10, 2016)

My home was completed in the fall of 2014. That winter I noticed a crack in the drywall in my great room. The truss spans about 45 ft and crosses over an 8' doorway in the middle. One side is cathedral ceiling and the other is 8'. The crack is where the truss sits on the interior wall and closed in the summer. Is this truss uplift? If so, any ideas what can be done?


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## arnoldat30 (Feb 10, 2016)

Here are pics of the cracks on each side of the doorway


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## arnoldat30 (Feb 10, 2016)

Another pic


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## nealtw (Feb 10, 2016)

That is what it looks like. Usually the truss company does not have the truss land above the wall like that. If you have access to that attic space behind. You would be looking to see if there is a wall there are if they nailed the drywall on the side of the truss or what exactly they did.


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## bud16415 (Feb 10, 2016)

Looks like truss lift as well to me. 

As the house is that new I would get the builder back in and have a talk with him before I did anything.


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## bud16415 (Feb 10, 2016)

nealtw said:


> That is what it looks like. Usually the truss company does not have the truss land above the wall like that. If you have access to that attic space behind. You would be looking to see if there is a wall there are if they nailed the drywall on the side of the truss or what exactly they did.



I dont have much experience with truss construction like Neal has but when we built my nephews house we had a similar situation but the trusses were not as long and we talked it over because the truss was landing right on a wall like that and to be finished and I told him to connect that bottom cord really well to the wall. We pulled it down tight and shot it in good and he never had an issue with lifting. I dont know if thats right or wrong actually maybe Neal will comment.


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## inspectorD (Feb 10, 2016)

Best bet is to contact the builder, most likely you have a one year guarantee on the home, but he may be willing to come back and fix the issue.
Have them contact the truss company and the engineer to find the solution to the problem. Most likely you will have to modify the truss a bit , but do not screw it down in the middle to attach it to the wall. There are certain points that a truss can be attached, and others that do not work as well.

Let us know what you find out by the experts.


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## nealtw (Feb 10, 2016)

bud16415 said:


> I dont have much experience with truss construction like Neal has but when we built my nephews house we had a similar situation but the trusses were not as long and we talked it over because the truss was landing right on a wall like that and to be finished and I told him to connect that bottom cord really well to the wall. We pulled it down tight and shot it in good and he never had an issue with lifting. I dont know if thats right or wrong actually maybe Neal will comment.



We always tacked them down so the walls stay in place. If you really attach them you can have the wall moving anywhere in the structure, usually it lifts off the floor and all the doors go out of wack seasonally


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## nealtw (Feb 10, 2016)

It would be real interesting to hear what the contractor, builder, truss company, city inspector, have to say about it.
They will come up with ways to hide it, fixing it would be expensive. The gable at the other end doesn't lift because it was sheeted and if that is the truss there, the fix should be to remove the drywall and sheet it tiing the truss to the wall and replace the drywall.


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## bud16415 (Feb 10, 2016)

If it was my own house and it had been around a long time and it was my responsibility to fix it or live with it I might just hide it with a painted trim strip. On the other hand its new construction and a lot of problems never show up until a seasonal cycle and that wasn&#8217;t done right and should be fixed at no cost to you. IMO. It is a job but not a huge job and if I was the builder I would rather fix it and have a happy costumer than one that&#8217;s telling all their friends when they come to visit and ask about it who the builder was.


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## nealtw (Feb 10, 2016)

bud16415 said:


> If it was my own house and it had been around a long time and it was my responsibility to fix it or live with it I might just hide it with a painted trim strip. On the other hand its new construction and a lot of problems never show up until a seasonal cycle and that wasnt done right and should be fixed at no cost to you. IMO. It is a job but not a huge job and if I was the builder I would rather fix it and have a happy costumer than one thats telling all their friends when they come to visit and ask about it who the builder was.



Up here the builder posts a bond with the  warranty company so, they fix things and charge it back to the builder if he won't fix it..
In order to hide it with trim you would have to add a bulk head at the hallway and other opening.


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## arnoldat30 (Feb 10, 2016)

Well, I actually built the house myself. I have a basic knowledge of framing but did have help from people who know what they are doing. I just put the trusses where the truss company designed. The drywall is screwed to the truss. The truss is nailed to those walls in a few places. It was not a gable truss, I had to add the other webs in myself. Don't wanna tear the drywall off. Thought about shimming it up where it is now and fixing crack. Is that dumb? Would it just raise more next winter.


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## nealtw (Feb 10, 2016)

arnoldat30 said:


> Well, I actually built the house myself. I have a basic knowledge of framing but did have help from people who know what they are doing. I just put the trusses where the truss company designed. The drywall is screwed to the truss. The truss is nailed to those walls in a few places. It was not a gable truss, I had to add the other webs in myself. Don't wanna tear the drywall off. Thought about shimming it up where it is now and fixing crack. Is that dumb? Would it just raise more next winter.



You don't happen to still have the map the truss company gave you? I would call them, they have run into this more times than anyone here, so they will know what works and what doesn't.


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## bud16415 (Feb 11, 2016)

Do your research as Neal mentioned and in the end you will have to try something. 
What&#8217;s your climate like? If there is no rush to fix it I would wait and watch it when the weather warms and see what it does. If it closes up I would say that&#8217;s going to be a yearly cycle. 

A few nails will pull right out with that kind of expansion and contraction. If I was going to shim and or close the joint I would then screw it together with deck screws and you could do that with just poking some holes in the drywall. As mentioned above The movement might come down thru the wall or go some other direction anyone&#8217;s guess. 

Can you get at it from above?


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## bud16415 (Feb 11, 2016)

Chances are when you added in the other &#8220;webs&#8221; to nail the drywall to you strengthened that truss quite a bit and now when the climate changes it contracts in some members more than others that are in the warm zone in the insulation and the truss arches. The cracks seem to show that as they opened in the middle of the span. Not that it may not matter but is the high ceiling trusses also rafter framed?


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## nealtw (Feb 11, 2016)

All the experts will tell you that the uplift is cause by moisture and a warm bottom cord.
I think that is more about, it's the one thing that is hard to argue.
In the picture you can see the last scissor truss is beyond the wall or just in front of the wall and a wall is constructed above the wall, I have never seen it done any other way.
That is why I questioned the map the truss company supplied. Usually there is one bay between trusses,  it would be an easy mistake to think it would be easier just to move the odd bay and make that truss line up with the wall.
Or it could be just starting the layout from the wrong end of the building.


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## arnoldat30 (Feb 11, 2016)

I live in central Indiana. I can get to the back of the wall/truss. It was set right on top of the wall. I could not find the map from the truss company, but it would not have been possible to start from the wrong side. The house is not symmetrical, but the trusses on the other side of the room also land right on top of the walls. No issues over there though.  The high ceiling is built with scissor trusses. In hindsight, yes a wall all the way up to another scissor truss would have definitely been the way to do it. Still going to try and contact the truss people and see what they say about it. This is the best picture that I could find of the wall before drywall. Kinda fuzzy but that is the wall right there with the doorway visible


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## nealtw (Feb 11, 2016)

So you filled in the studs for the drywall. Did you add to the back for insulation?
What floor do you have, basement or?


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## arnoldat30 (Feb 11, 2016)

Yes, it is insulated. Basement underneath with 12" I joists


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## nealtw (Feb 11, 2016)

arnoldat30 said:


> Yes, it is insulated. Basement underneath with 12" I joists



At first I said the gable end never gave us any trouble, but in thinking about that, I don't know. That outside truss would be set on the outside wall and then the wall was built with the studs notched out for the members of the truss and toe nailed in place. So given that I suppose the gable could move with out lifting the wall.
If you have a wall below this in the basement we could look at bolting to the slab with seismic hard wear.


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## inspectorD (Feb 13, 2016)

Ok, another question.
Where is the main carry beam in the basement, and what is it made of. Dimensional lumber or LVL.
Pier under the opening may have sank.

Another is, I wonder if you have any blocking to the lower truss cord where the opening is. You can also get lateral movement at the top of the opening, which is the bottom of the truss cord.

Wind plays a part also on trusses, not just heat.


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## arnoldat30 (Feb 14, 2016)

Two beams in the basement. One on each side of the opening, or so. No evidence of anything sinking. Sinking is the first thing I checked for. The crack closes back up in the summer. There is no lateral movement, or at least not that I can see.


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## inspectorD (Feb 15, 2016)

arnoldat30 said:


> Two beams in the basement. One on each side of the opening, or so. No evidence of anything sinking. Sinking is the first thing I checked for. The crack closes back up in the summer. There is no lateral movement, or at least not that I can see.



If its dimensional lumber ..measure it.. I have had homes that the baseboard on the 3rd floor had a gap or 3/4 at the floor. All from the joists each shrinking half an inch during the winter months. Its amazing how much some homes move, and others do not. Depends on climate and conditions. 
I think it could be a couple things at the same time in my opinion. 

But one of those 3 things are causing that crack.


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## nealtw (Feb 15, 2016)

inspectorD said:


> If its dimensional lumber ..measure it.. I have had homes that the baseboard on the 3rd floor had a gap or 3/4 at the floor. All from the joists each shrinking half an inch during the winter months. Its amazing how much some homes move, and others do not. Depends on climate and conditions.
> I think it could be a couple things at the same time in my opinion.
> 
> But one of those 3 things are causing that crack.



If all the walls have the same number of plates, it would take extreme condition for the outside wall plates to expand that much and the gap would continue to the outside wall.??


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## nealtw (Feb 15, 2016)

Simpson has a continues rod system that would bolt the truss thru one of those walls to the beam below if not the floor, they have a ratcheting nut so as the shrinkage occurs the nut tightens and holds it in place.


The RTUD ratcheting take-up device is a cost-effective shrinkage compensation solution for continuous rod systems. The RTUD is now code-listed for use with rod systems to ensure highly reliable performance in a device that allows for unlimited shrinkage. Once the RTUD is installed, a series of internal threaded wedges enable the device to ratchet down the rod as the wood structure shrinks, but engage the rod in the reverse direction when under tensile loading. Continuous engagement is maintained on the rod at all times by the take-up device, enabling the rod system to perform as designed from the time of installation.

Key Features

Maintains rod-system tightness, allowing it to perform as designed
Pass-through design provides unlimited shrinkage compensation
Available for 1/2", 5/8" and 3/4" diameter threaded rod
Fastens easily to the wood plate with the BPRTUD bearing plate and (2) 8dx1 1/2" nails (minimum) or (2) #9x1 1/2" Strong-Drive® SD Connector screws (not included)
1.33-degree rod offset (1 3/4" max) allowed per floor
Very minimal force required to allow rod to pass through take-up device to mitigate rod buckling during wood shrinkage
Material


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## inspectorD (Feb 15, 2016)

nealtw said:


> If all the walls have the same number of plates, it would take extreme condition for the outside wall plates to expand that much and the gap would continue to the outside wall.??



Its the interior of the building. The main beam shrinks but the concrete foundation walls stay put. The outside walls also have the stress skin of the plywood so not as much movement happens at the exterior. The interior walls fall inward so to speak.  
Look at a fireplace exterior and look at the floor in front of it. The floor usually always slopes away from the hearth due to shrinkage.

The truss is the culprit at that seam... the solution is to find the movement.
To do that you need an engineer to see what can be modified at that connection for the truss.


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## bud16415 (Feb 15, 2016)

That end truss wasn&#8217;t supposed to be a truss. You have the butterfly truss next to it to take the load. When he filled it in to have something to put the drywall on he made it into a truss with all the vertical studs attached top and bottom. Those studs are pulling up and forming the crack at the plate. I think I would block all the studs together on the back and then cut them free at the top. You will still get the movement at the top and a molding up there could cover it.  

At least that&#8217;s what I see happening.


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## nealtw (Feb 15, 2016)

bud16415 said:


> That end truss wasnt supposed to be a truss. You have the butterfly truss next to it to take the load. When he filled it in to have something to put the drywall on he made it into a truss with all the vertical studs attached top and bottom. Those studs are pulling up and forming the crack at the plate. I think I would block all the studs together on the back and then cut them free at the top. You will still get the movement at the top and a molding up there could cover it.
> 
> At least thats what I see happening.



I think you are looking at the wrong picture, his truss is flat bottom with fillers for drywall, I posted the other one showing a wall beside the scissor truss.


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## nealtw (Feb 15, 2016)

inspectorD said:


> Its the interior of the building. The main beam shrinks but the concrete foundation walls stay put. The outside walls also have the stress skin of the plywood so not as much movement happens at the exterior. The interior walls fall inward so to speak.
> Look at a fireplace exterior and look at the floor in front of it. The floor usually always slopes away from the hearth due to shrinkage.
> 
> The truss is the culprit at that seam... the solution is to find the movement.
> To do that you need an engineer to see what can be modified at that connection for the truss.



The fireplace is an insert sitting on the floor so there will be nothing to see there. A string line strung across at the height of the outside walls will prove a sag in the floor or the uplift of the truss.


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## bud16415 (Feb 15, 2016)

nealtw said:


> I think you are looking at the wrong picture, his truss is flat bottom with fillers for drywall, I posted the other one showing a wall beside the scissor truss.



Oh I see that now, his was a truss he just added a bunch of studs to it. 

So he has no butterfly truss at the end?? What is his insulation stapled to? 

A trim strip over the crack is looking better all the time.


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## nealtw (Feb 15, 2016)

bud16415 said:


> Oh I see that now, his was a truss he just added a bunch of studs to it.
> 
> So he has no butterfly truss at the end?? What is his insulation stapled to?
> 
> A trim strip over the crack is looking better all the time.



They would have added a 2x4 to this side to match the scissor for the ceiling drywall and insulation.


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## inspectorD (Feb 15, 2016)

nealtw said:


> The fireplace is an insert sitting on the floor so there will be nothing to see there. A string line strung across at the height of the outside walls will prove a sag in the floor or the uplift of the truss.



Sorry Neal..I meant looking at a fireplace as an example of joists shrinking. Not this particular one.


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## nealtw (Feb 15, 2016)

inspectorD said:


> Sorry Neal..I meant looking at a fireplace as an example of joists shrinking. Not this particular one.



I know, I was just clarifying


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## nealtw (Feb 15, 2016)

arnoldat30 said:


> Two beams in the basement. One on each side of the opening, or so. No evidence of anything sinking. Sinking is the first thing I checked for. The crack closes back up in the summer. There is no lateral movement, or at least not that I can see.



What did you build behind that truss for the insulation.


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## arnoldat30 (Feb 16, 2016)

There is batting coming down about 16 inches from lower ceiling. Then 19 inches of blown in covering the remaining 16 inches and the other ceiling.


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## nealtw (Feb 16, 2016)

The construction holding the batting??


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## arnoldat30 (Feb 16, 2016)

If I understand what you are asking, the batting is stapled on the 2x4s and I have some netting stuff on the back side holding it


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## nealtw (Feb 16, 2016)

arnoldat30 said:


> If I understand what you are asking, the batting is stapled on the 2x4s and I have some netting stuff on the back side holding it


We would have built a wall behind that truss just for the insulation.
I have a fix but it won't be easy and you might be able to save the drywall.
I think it would be best when the gap has closed. 
The trick will be to build a wall for the drywall and allow the truss to move.
I talked to a drywall hanger who has seen this before and they request the framing to be a 2x6 wall with the studs cut to go thru the truss with clearance for movement. Then they only screw the drywall to the studs and the would not screw the ceiling to the 2x4 that is on the face of the truss.

My next question was how do we do that now? And he had an answer.
So with a stud finder you can find the screws in the drywall and remove most of them.
From the attic side, remove the studs that were added to the truss.
2x4 bottom plate with a half in space between the truss and the plate.
2x6 studs with slightly over sized notches to clear the members of the truss
2x4 top plate, plumb the wall and brace it back to other trusses in the attic.
Re screw drywall to the new studs and remove the remaining screws that are into the truss.
He said if you have a sprayed ceiling and you don't want to remove screws into that 2x4 above you could pull the nails and let the 2x4 float too.

This doesn't sound like fun but the drywall would be one with the lower wall and the truss would be allowed to move up and down. for inspector, the walls could move up and down.

Thought?


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## inspectorD (Feb 17, 2016)

nealtw said:


> We would have built a wall behind that truss just for the insulation.
> I have a fix but it won't be easy and you might be able to save the drywall.
> I think it would be best when the gap has closed.
> The trick will be to build a wall for the drywall and allow the truss to move.
> ...



Sure the walls will stay where they are, and the truss will move. But that only means the crack is not at the lower wall, the wall ceiling joint will give somewhere if you do not remove the ceiling screws at the edges. 
And that only works if there is enough play, which there usually is not. This is why folks install pieces of floating trim at those joints.
The truss clips, {everyone never uses} are what is needed. Then the wall is connected and floats with the truss.


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## nealtw (Feb 17, 2016)

inspectorD said:


> Sure the walls will stay where they are, and the truss will move. But that only means the crack is not at the lower wall, the wall ceiling joint will give somewhere if you do not remove the ceiling screws at the edges.
> And that only works if there is enough play, which there usually is not. This is why folks install pieces of floating trim at those joints.
> The truss clips, {everyone never uses} are what is needed. Then the wall is connected and floats with the truss.



This us how they want the built before they drywall.
Even if it is tight and the drywall is only screwed to the studs, the back of the drywall will be scuffed.
The ceiling would be a concern, I think you are right, about removing screws there if there are any.


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## nealtw (Feb 17, 2016)

If this is caused by moisture, we should be talking about attic venting.


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## bud16415 (Feb 17, 2016)

nealtw said:


> If this is caused by moisture, we should be talking about attic venting.



More than likely in the winter it is too dry up there.


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## nealtw (Feb 17, 2016)

bud16415 said:


> More than likely in the winter it is too dry up there.



I have been reading all the "experts" are saying it is the top member aborbing moisture. The long expansion from very dry to very wet is .1%
So if the top cord is 40 ft you might get to 1/2 inch. I figure if the roof pitch is 12/12, some one could do the math if side c is 1/4 longer and side a is constant side b will be.
If you believe that, it has to get very wet in the attic in every house in the country because the gap is about average.
If they are correct, in the summer you could go paint the top cord and stop moisture absorption by a great %age


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## bud16415 (Feb 17, 2016)

I&#8217;m thinking it is temp in the winter the bottom stays warm.


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## nealtw (Feb 17, 2016)

That is part of the "experts" argument.
So you are thinking the top cord shrinks like steel. Find a chart for that.
That might be a better argument.


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## bud16415 (Feb 17, 2016)

http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html


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## nealtw (Feb 17, 2016)

But the Epoxy people will tell you that it is the same as wood.
I am not even try the math to figure it out.
If the top cord on both sides of the roof shrink at the same rate with cooler temp, that would lower the center of the roof and push the upright members down so it would counter any swelling going on from moisture. yes, no?
So you would subtract one from the other making moisture even harder to believe.

I think someone has just grabbed the first hand full of straw they could. They claim insulating the roof sheeting will solve it, wonder if I can find something to prove that.


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## slownsteady (Feb 18, 2016)

I know "zero" about trusses, so let me ask the dumb question: why doesn't this happen to stick-built houses? After all, once it's all nailed together it is essentially the same thing???


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## nealtw (Feb 18, 2016)

slownsteady said:


> I know "zero" about trusses, so let me ask the dumb question: why doesn't this happen to stick-built houses? After all, once it's all nailed together it is essentially the same thing???



Hand framed rafters may come into contact with a ceiling joist over the wall but that is about all.
The tie in the top third of the rafter ties  the two together so between the tie and the wall the rafter could do what ever it want to with out having any effect
on the ceiling joist which is sitting on and nailed to a bearing wall in the middle.

A truss may have 3, 4, 5, or six members that join the ceiling member to the rafter member.


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## slownsteady (Feb 18, 2016)

So in a stick-built house the ceiling joists on the top floor are totally independent from the roof structure. But in a truss construction, the bottom member of the truss is the ceiling joist?


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## nealtw (Feb 18, 2016)

Yes,, samples, they all have names but for most framers they are just called trusses with just a few extra word, like girder, jacks and corners'
They are delivered to the top of the house in bundles and no one cares what design theyy are just do they fit and are they in the right order.


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## arnoldat30 (Feb 18, 2016)

Venting in the attic should be fine, at least as far as I can figure. About 50' of ridge vent and 2 gable vents. Back soffit is all vented, about 62', and front is half vented. Rafter vents on both front and back the whole way. Figured it all up when building and it was okay numbers wise. I have an email in to the truss manufacturer and designer to see what they have to say about it.


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## oldognewtrick (Feb 18, 2016)

What type of ridge vent? Roll Cobra mesh type or hard plastic, 4' sections?


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## arnoldat30 (Feb 18, 2016)

Hard plastic


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## oldognewtrick (Feb 18, 2016)

arnoldat30 said:


> Hard plastic



Looking at the ridge vent from the attic, do you see a void between the decking of about 3" ?


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## arnoldat30 (Feb 18, 2016)

Yep, I think that I left the decking down three on each side


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## mudmixer (Feb 18, 2016)

Truss uplift varies on the climate. A big difference geographically.

In the cold, dry north the uplift effects come from the bottom cord that is buried and covered with insulation. That minimized the temperature effects, so the diagonals a much colder in the winter if there is good ventilation above the ceiling insulation. - This leads to the diagonals and top chords becoming shorter and pulling up the total truss upward, causing the cracks in dry wall joints.

It is worse on the interior walls because the temperature effects are a little less than the exterior walls there the trussed a held in place better.

It is a little different where the temperatures and are more constant.

Any truss will move with loads, temperature and moisture.

Dick


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## nealtw (Feb 18, 2016)

mudmixer said:


> Truss uplift varies on the climate. A big difference geographically.
> 
> In the cold, dry north the uplift effects come from the bottom cord that is buried and covered with insulation. That minimized the temperature effects, so the diagonals a much colder in the winter if there is good ventilation above the ceiling insulation. - This leads to the diagonals and top chords becoming shorter and pulling up the total truss upward, causing the cracks in dry wall joints.
> 
> ...



That is the theory. Have you seen any studies that prove it or tell you what the force is? I can't find anything that sounds scientific.


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## arnoldat30 (Feb 18, 2016)

I can see it in my hallway, it runs perpendicular to the trusses. The drywall lifts where the wall and ceiling meet. Comes back down in the summer. You can just see the tape pulling, doesn't leave a crack, most people probably never see it. In hind sight, there are a few things that I would do different.


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## nealtw (Feb 18, 2016)

arnoldat30 said:


> I can see it in my hallway, it runs perpendicular to the trusses. The drywall lifts where the wall and ceiling meet. Comes back down in the summer. You can just see the tape pulling, doesn't leave a crack, most people probably never see it. In hind sight, there are a few things that I would do different.



In the hall way there should be no screws in the ceiling close to the wall.
2x6 backing on the wall between the trusses would have been a good idea.

For the main room I think your best bet would be to make a header in the openings, not connected to the truss and then a molding only nailed to the lower wall.


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## mudmixer (Feb 18, 2016)

neal -

You should know there are no statistics on the various situations, let alone any engineering calculations. Unfortunately there are few situations that are the same and could be due to different details/plans/conditions/climates.

The practice of keeping the nails or screws well away from the wall/ceiling joint has been a common practice for about 50 years around here.

I expected some problems with my own lake home (I held the ceiling sheet rock nailing away from the wall/ceiling joint) that had 9' walls and scissor trusses spanning 28', but the house had tremendous thermal storage. Maybe the height of the walls provided some "give". But it saw winter temps at up to -42F and then heating up to 70F before I got there for a week-end thanks to a programmable thermostat.

Despite being an engineer, I can only offer anecdotal observations that would not be adequate for requirements on the code committees is an active in.

Dick


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## nealtw (Feb 18, 2016)

mudmixer said:


> neal -
> 
> You should know there are no statistics on the various situations, let alone any engineering calculations. Unfortunately there are few situations that are the same and could be due to different details/plans/conditions/climates.
> 
> ...



Thanks Dick, I understand that and have been explaining it to home owners for years. I am just trying make it work in my head with what I have seen in the field. We see a vaulted ceiling with a full gable over the outside wall all the time. We often just added studs to the back of the gable that are notched out for the members in the truss. So in this case the wall and the truss are built together or tied together so much like the problem here.
I have never seen a problem with the gable lifting.
The gable has more upright members that the other trusses.
So is it the extra members, or the sheeting on the outside, or is it the proximity to the cold and moisture that keeps it down.

The truss company should be aware of what ever the problem is and should have shipped a gable and or called for sheeting or shipped an extra truss so that one didn't have to land on the wall.

I have never seen a house with concrete tile have an uplift problem so in my head, you could hold it down but with what force and how to attach to it.


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## oldognewtrick (Feb 19, 2016)

Neal, the dead load from a asphalt shingle is less than 300 lbs per square compared to sometimes 4-5 times that for most hard surface installations.


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## nealtw (Feb 19, 2016)

oldognewtrick said:


> Neal, the dead load from a asphalt shingle is less than 300 lbs per square compared to sometimes 4-5 times that for most hard surface installations.



That's my point, they can be held down. I can't believe that all this theory is kicked around and there is no data to be had.


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## oldognewtrick (Feb 19, 2016)

Standards and building science are moving targets. What's gospel today is heresy tomorrow.


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## nealtw (Feb 19, 2016)

I would like to see a chart the says if member A has this moisture and B has this moisture it will lift X per foot of run. You can be sure someone tried to do that and when it doesn't add up they just shut up.


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## bud16415 (Feb 19, 2016)

There is a plastic angle strip for normal wall to ceiling edges and you screw the drywall to the plastic angle a couple places between the truss. The plastic angle is attached to the truss. Gives a place to screw to but allows the movement. His is different because the wall extends up the truss. The way I would think that should be built is hold the truss back 4 or 5 inches and then frame a wall up to the ceiling height and then use the plastic angle for any movement at the ceiling.

What he has now is a problem as you cant easily move the truss. He could build a new wall out a few inches but that&#8217;s also a PITA with the fireplace and all.


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## bud16415 (Feb 19, 2016)

As to the expansion with heat I found some numbers for wood. It was something like 1/3 steel but had a huge range by type of wood. I ran the number for a 40 span and a temp range of 80 degrees and it came out to 1/8


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## nealtw (Feb 19, 2016)

bud16415 said:


> As to the expansion with heat I found some numbers for wood. It was something like 1/3 steel but had a huge range by type of wood. I ran the number for a 40 span and a temp range of 80 degrees and it came out to 1/8



They talk about wet and cold like they were added together.
But very dry to very wet for 40 ft is about 3/8.
Subtract your very warm to very cold 1/8.
Just does not compute.
There is a chart on page 4
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/ch12.pdf

EMC values were determined from the average of 30 or more years of relative humidity and temperature data
 available from the National Climatic Data Center of the National Oceanic and Atmospheric Administration

dry lumber is between 6 and 8%, I don't think 15% is what you would call very 
wet


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## Harvey Juric (Mar 16, 2016)

It does not look like truss uplift. It looks like they framed the wall in 2 sections, wrongly installed drywall (drywall joint at the same place as 2"x4" pony wall joint), and the wood dried out.  

Another reason may be that the top part of the wall is nailed more securely to the truss than the bottom wall. The truss will actually lift the entire wall. This may account for the difference in width of the crack. It is larger towards the middle of the room.

In any case, it is all about the moisture in the wood framing components of the home.

I have posted an article on humidity in new homes here: http://buildersontario.com/humidity-new-home


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## arnoldat30 (Mar 17, 2016)

I assume that is has to do with moisture in the wood. It closes back up in the summer. I know that it was not done correctly, just looking for advice on how to fix it without tearing the whole wall apart.


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## arnoldat30 (Mar 17, 2016)

I also have an indoor wood furnace which dries the air out quite a bit. I installed an aprilaire steam humidifier this winter which keeps my humidity in check but still didn't help with the crack.


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## nealtw (Mar 17, 2016)

arnoldat30 said:


> I also have an indoor wood furnace which dries the air out quite a bit. I installed an aprilaire steam humidifier this winter which keeps my humidity in check but still didn't help with the crack.



You likely have vapour bearier so moisture or lack of it in the house won't help or hurt the trusses.
Have you talked to the truss people?
Is that a barring wall below it?


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