Drywall Ceiling Before Framing Interior Walls
Last Post 23 Sep 2010 08:43 PM by Garth Sproule. 32 Replies.
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stonecavemanUser is Offline
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25 Aug 2010 11:31 AM
Is there any reason to frame/erect the interior walls before drywalling the ceiling?  I have an area about 40x25 which will be divided into bedrooms.  The roof is clearspanned with flat trusses.  Since the space is empty, it would be easy to get the drywall lift in there and drywall the ceiling.  This would also seem to provide a good air barrier (no breaks around walls) and avoid problems with drywall cracking due to truss uplift - the drywall would never be attached to the walls, so movement of the truss relative to the wall would not cause a problem.

Then build the interior partition walls (none are load bearing) and attach to the trusses/blocking with L-shaped truss clips (caulk the holes), trim out the top of the walls to cover the gap between the wall  and ceiling and move in.  (Probably fill the gap with acoustic sealant to minimize noise).

Since no one seems to do this, I assume that there are a vast number of problems that I've missed that mean this won't work or that I will suffer greatly with this approach (usually the problem with my "good" ideas).  The electrical inspector will probably dislike it since he'd have to climb in the attic (which is accessible) to inspect the ceiling wiring.
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25 Aug 2010 12:33 PM
Posted By stonecaveman on 25 Aug 2010 11:31 AM
Is there any reason to frame/erect the interior walls before drywalling the ceiling? 

Yes not only will the inspector dislike it , but he can very well demand that you remove it and be justified in doing so
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25 Aug 2010 12:45 PM
Chris,

Which inspector? The electrical? He can still inspect although it maybe a little more difficult. I'm not in the business of making an inspector's life more difficult (kinda like poking a sleeping tiger) but I'm also not required to make his life easier by making my life more difficult or compromising the building envelope.

Gotta love the state inspection scheduling here. Basically comes down to "could be any time in the next week and we're not going to give you any clue - not even the day - you might expect the inspector". Even the cable installer will tell you what day and usually morning or afternoon!
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25 Aug 2010 01:46 PM

Stonecaveman,

On a practical level my concern would be that you may not be able to pre-build the walls on the floor and stand them up if the ceiling drywall is already in place.  I suppose you could but the gap between the top plate and the drywall ceiling would have to be large enough to allow it.  Tilting the wall up as usual will require more clearance than thought because of the angle right before the wall is vertical.  However, if you want to install one stud at a time in the vertical position, then this will be much slower.  Also having the drywall ceiling in place before the interior walls will make it a little more difficult to locate the ceiling joist or additional blocking for attaching the metal clip to hold the wall in place.  In other words, installing the ceiling before the interior walls may make it easier and quicker for the drywaller, but I think it will cost the framer more time and you more money.

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25 Aug 2010 01:53 PM
stonecaveman;

I cannot envision and electrical inspector insector ever climing around an attic to inspect, now that I think about it further you will also be covering up framing, plumbing stack vents and exhaust duct vents , it will also make intallation of all those things very difficult. whatever ease you will make by installing drywall first will be terribly offset by the other installation problems by other tradesmen. If you are not doing those yourself , expect a hefty upcharge. All inspectors like work exposed and approved before covering up. I have seen first hand inspectors having drywall torn off.

Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
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25 Aug 2010 02:47 PM
My interest is not really in making the ceiling drywall easier, but in the benefit of air sealing that could be achieve by having continuous drywall. Since the insulation is cellulose, if the ceiling isn't sealed, then the R-value of the insulation will be severely reduced by infiltration.

There's extra effort either way. If you frame then drywall, someone has to go along the tops of the walls and seal the drywall. If you drywall then frame it makes the truss/wall joint more complex, but there would only be a couple of holes around the clips to caulk (and the lights and the wiring holes, etc. etc., but they're the same in either case). BTW, this is one more reason to use a SIP roof.

With the drywall in place we could either leave a big enough gap to angle the wall up or just set it on it's sole-plate after construction - kinda like a retrofit of dividing an existing room in half. Securing the truss clips would be a more effort, but it would be possible to install any required support blocking and the clips before the drywall (or while the drywall is still open). Since we're doing the work, we can coordinate the framing the drywall better than if separate subs were involved.

The inspector question is an interesting one. I've never heard of a plumbing/building/electrical inspector going into a crawl space to check work done there (I'm sure some do/have, but none of the limited set that I've met have) and this would seem to be the same situation. The space is accessible in more than the NEC interpretation of the word. Seems to me that, just like the crawl space, he can either pass it, or go and see if he likes it. Anyway, he's supposed to be here sometime this week so I'll ask him the question.

I'm sure that the inspectors have a love/hate relationship with homeowner permits. There are things I'm willing to do, such as solar air heaters, gray water systems, etc. not to mention odd/detail things to minimize infiltration and maximize insulation that would never be cost effective enough to make the mainstream. It confuses the permit issuers, but so far the inspectors have been more interested in the approach and attention to detail than in finding fault with the ideas and techniques. Of course, that could change any day depending on the inspector.
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25 Aug 2010 03:54 PM
I have observed code inspectors on some of my projects go into the attic and crawl space.  When I went with them they pointed out to me what they were checking and how it could be done better.  I have seen plumbers call for a rough-in inspection and then be upset when the code official found things intalled incorrectly.  In this case, the code official not only red flagged some of the work but told the plumbers how to correct it and that he would wait while they made the corrections so he would not be holding up the project.  I think this was very nice of the code official to care about the schedule.  Maybe in my area we truly have public servants.
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25 Aug 2010 04:27 PM
The infiltration will not be at the drywall, it will be at the penetrations made  for wiring and pipes at the top plate. The drywall at room ceiling corners will be sealed with tape and compound and will not let any apperciable air infitration at those points.
Efforts in other areas would be a better investment and would not upset the inspection process that could very well cause you a loss of time and money
Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
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25 Aug 2010 04:35 PM
I think that the inspectors, by and large, (there have to be exceptions) are willing to be helpful and not looking to be unreasonable.  The bureaucracy that surrounds them is another matter entirely.  We have to deal with some local (structural) and some state (everything else) inspectors which just adds a twist.  Getting the to sign off on permits - especially homeowner is not easy.  The zoning people seem to be a bigger problem still because they feel they have to enforce something even if it doesn't apply.

I think Chris has run into some more challenging inspectors - perhaps that's the life of a SIP builder.  I don't know the state inspectors, so have no idea who's reasonable and who's not.

I posted this humorous article by Scott Adams - the creator of Dilbert - on the challenges of designing and building a "Green Home" earlier this week.  It is a little close to the truth however, for example, we requested a plumbing permit with a gray water system.  The state environmental department allows 250 gallons per day by homeowners, but the UPC really doesn't cover such small systems, and so the construction division has no real guidance as to what to do (and doesn't know about the environment departments guidelines - which they should) so we may, or may not pass inspection even though we've installed what the permit detailed (full iso drawing).   Always assuming that the bureaucrats don't loose this inspection request - which they did with the previous one.
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25 Aug 2010 05:14 PM
Posted By stonecaveman on 25 Aug 2010 04:35 PM

I think Chris has run into some more challenging inspectors - perhaps that's the life of a SIP builder.  I don't know the state inspectors, so have no idea who's reasonable and who's not.



actually I have much for experience in conventional building methods that with SIPs, I have had far less inspection problems using SIPs than conventional methods.
 I just hate to see someone try to circumvent the normal process and find the hard way that their inspector has "Napolean" syndrome.

I will say that in most cases the inspectors give the"OB"much more lattitude than professionals, but I wouldn't try anything new or innovative without at least discussing it with the local building official
Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
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25 Aug 2010 05:36 PM
Posted By cmkavala on 25 Aug 2010 04:27 PM
The infiltration will not be at the drywall, it will be at the penetrations made  for wiring and pipes at the top plate. The drywall at room ceiling corners will be sealed with tape and compound and will not let any appreciable air infiltration at those points.
Efforts in other areas would be a better investment and would not upset the inspection process that could very well cause you a loss of time and money

With 25'+ trusses, even though the climate is dry, I have some concerns about drywall cracking due to truss uplift.  If the plan is to mud/tape the top, then it take a little effort (not too much) to make sure that the drywall is not attached to the trusses close to the wall, but is instead attached to the walls - so something like a 1x6 along the top of the wall to give a nailer for the drywall.  My preference would be not to mud that interface, but to just add some molding, but, as you say, that it could be sealed using an acoustic sealant, caulk or similar behind the molding.

I think that you'd also need to seal the drywall on the wall to the top plate of the wall and the nailer to the top plate (again the acoustic/SIP sealant idea) to avoid infiltration from outlets, switch, etc.  Or you could foam the outlets as if it were an outside wall.  I don't really know whether this would be a significant infiltration problem on an interior wall, but it certainly is on an exterior wall.  Foaming, or acoustic sealant around outlets has the advantage of helping with an acoustic barrier also.  As does insulating the inside walls which would be effective in slowing air movement.

Unless you just assume that infiltration through the drywall is negligible then every piece of drywall would need to be sealed to eliminate any infiltration.  Anywhere that air could get past the drywall would need a bead of caulk or seal - around every opening.  This is about what's advocated by the Airtight Drywall Approach (ADA) albeit in that case primarily with exterior walls.

With the ceiling-first approach, you put up the drywall, tape and mud (and caulk?) all the seams and finish any areas that would be visible.  You'd also need to caulk the drywall-exterior wall interface.  Then you just seal every hole you make through the drywall.

I'll probably take the conventional approach just because the risks and issues are well understood.  However, unless the inspector objects when I talk to him, the amount of effort to get an absolutely airtight seal seems to favor the ceiling first.  Of course, if I go that route, I might change my mind after crawling around the attic with wiring, putting my foot through the drywall in a few places and skewering myself repeatedly on the screws and nails that stick through the OSB on the roof!
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25 Aug 2010 07:12 PM
Hmmmmm............. interesting, I always refered to ADA in the building realm as the Americans with Disabilities Act, but I could be wrong.

You may want to deterimine where the most infiltration occurs ( not the drywall)  , but good luck with the build whichever direction you choose to go
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25 Aug 2010 08:16 PM
The easiest way in my opinion is to build conventional. Fasten poly strips on top of all interior partition walls then set the trusses. You now have poly to seal the room ceiling poly to that is above the plate (what you are trying to accomplish). After the truss set when you put in your lateral bracing use truss clips where the trusses intersect interior walls.

You can do this if you need to build interior walls after a truss set but its more difficult for walls that are perpindicular to trusses because of the tight top plate. To prevent uplift cracks your drywaller needs to float ceiling corners or keep the screws back from the corners so when the trusses lift, if they do, the drywall will flex with the uplift and you'll avoid any cracking.

ADA is both Chris.
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25 Aug 2010 08:43 PM
greentree, 

the paradox being........... if you float the corners , then you can't caulk the backside of the drywall
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25 Aug 2010 09:56 PM
take it from someone who knows, crazy ideas get you no where
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25 Aug 2010 09:59 PM
Posted By cmkavala on 25 Aug 2010 07:12 PM
You may want to deterimine where the most infiltration occurs ( not the drywall)

Well, yes, but the problem is it's really hard to determine where the infiltration occurs until after you've built the house.  I really wish I'd counted the sealants, some 60+ tubes of SIP sealants as well as probably close to that number of cans of foam and a bunch of caulk - and we're not through yet.  BUT there's one heck of a lot of drywall that we're all relying on as a infiltration barrier.  The energy savings from sealing drywall (again, mostly the exterior walls) is impressive:

"After a year of monitoring, one study found that the ADA house had 0.67–1.80 air changes per hour (ACH) at 50 Pascals pressure. An identical conventional home without ADA had a 2.23–2.59 ACH at 50 Pascals."


I can't find any numbers on the net for ceiling drywall infiltration.  The normal advice (caulk around all electrical) but no hard data.  One reason to think that it is significant is that SIP roof perform well because they limit infiltration, they seal well, rather than raw R-Value.  If the ceiling drywall was a good seal I'd expect fiberglass/cellulose to perform just about as well.

It's also a hard error to fix later.  Digging through 18"+ of cellulose to caulk/seal the top of a wall is not appealing.

Greentree, your basic approach is to seal the top of the wall and you could probably apply it to walls before you stand them up even with the trusses in place.  Especially if you're going to use truss clips and can leave a little space.  As Chris says, I would still worry about the ceiling drywall seal at the walls.  By the time you've done all that would it be easier than standing up a wall with the ceiling drywall in place and then just sealing the screw holes from the truss clips?

I was really expecting some to tell me why the idea was completely stupid.  What I think I understand from the discussion is that the interior partitions will have some additional challenges, but that the conventional approach has some issues with sealing and floating drywall that, while fairly well understood are not a totally trivial problem to solve.  The conventional approach would take more time/effort in the details of sealing than would the ceiling first approach.



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25 Aug 2010 10:12 PM
Posted By Jelly on 25 Aug 2010 09:56 PM
take it from someone who knows, crazy ideas get you no where

Cockamamy is the word that one of my friends applies to the whole project.  Take a house built in 1950/51 put a SIP second storey on it, reside the first storey with 3.5" of polyiso under the siding and seal everything that you can possibly find.  Add solar air panels (built onto the south wall - with the old tar/gravel roof as a thermal mass), solar hot water, gray water system, etc.  Oh, and the second storey is bigger than the first, which leads to some very creative insulation/sealing problems involving cantilevers.

Hey, but we're talking drywall, something must be progressing!


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25 Aug 2010 10:13 PM
Posted By stonecaveman on 25 Aug 2010 09:59 PM

Well, yes, but the problem is it's really hard to determine where the infiltration occurs until after you've built the house.  



that is a very true statement and the reason why you should rely on the data of others that have built before you so you don't duplicate their mistakes.

One of the most common sources of air infiltration is the sill plate
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25 Aug 2010 10:36 PM
Posted By cmkavala on 25 Aug 2010 10:13 PM

that is a very true statement and the reason why you should rely on the data of others that have built before you so you don't duplicate their mistakes.


True.  Have you had any more success than I in finding drywall infiltration data?

Posted By cmkavala on 25 Aug 2010 10:13 PM

One of the most common sources of air infiltration is the sill plate

The real problem is where to stop.  The obvious and common get attention.  We have 3.5" of PolyISO over the whole wall and extending down below the sill, sealed with spray foam, so (hopefully) we have that covered.  SIP walls in the addition (second storey), new windows (mostly) taped and foamed.  Crawl space insulation/sealing is probably the next biggest source.  I don't think that there's much doubt that electrical boxes in the exterior walls and ceilings should be sealed.  Drywall to the exterior walls seems to have good data supporting the need to seal.

If I could find a source of infiltration that merited more attention than ceiling drywall I'd address it.  The other area that is probably missed in cellulose fill is any gaps in the infill in between the trusses.  With energy heal trusses you usually have 16"+ of "something" filling in the space between the top plate and the roof.  Typically this is cardboard stapled between the trusses, which is pretty good against infiltration, but needs to be caulked/foam where it touches the trusses to ensure that it's sealed.  Just staples will leave a gap at each truss.

Cellulose is such a bad air barrier that almost any infiltration is going to have a major negative impact on it's performance.  I think much more so than fiberglass.
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25 Aug 2010 11:09 PM
The tests that I have witnessed show that more air goes through fiberglass than cellulose.  I wonder if Dana1 has data one way or the other.
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