Truss Lifting and Crown Moulding

Trim installers discuss the finish problems associated with seasonal truss movement ó cracking at the corners where walls meet ceilings. June 4, 2009

I have a center hall colonial house with vaulted ceilings. I installed crown directly to the wall and ceiling as we usually do. Truss movement made the crown look horrible. Iím thinking of reversing a piece of base and fastening it to wall then fastening crown directly to base and not to ceiling. Does anyone have any experience with this?

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor G:
Just like you said, you need to attach it to the ceiling only. That way it will rise and fall and it will slide up and down on the wall. The only downfall is you cannot caulk it - it looks bad to me when you can see it. If it is stained then you won't really notice.

From contributor D:
I've installed a lot of crown in my life and always nailed it to both the wall and ceiling. I have never had a problem doing it this way. I have returned to houses years later and the crown still looks good. The trusses shouldn't move to the extent that it screws up crown. What if the crown wasn't there, would it move so much as to crack the sheetrock? If so, then I think there is a bigger problem somewhere.

From contributor G:
The trusses they are producing now move a lot. They span large spaces and have intricate webbing that will support great weights. But, from winter to summer there is an uplift in the truss. I have seen 1/2". It can rip the sheetrock tape and lift walls if you attach them to the truss. It is something that has come from modern construction. An older home will never have this type of lift happen.

From contributor A:
Contributor D - you're right as far as ripping the tape and etc. This is why I put the crown to begin with. Contributor G - I'm glad you agree, however you're right and Iím wrong because if you read my original post it says attach to the wall and not the ceiling, that wouldnít solve anything. So far Iím going to go your way except if someone comes up with a better idea. I donít feel like climbing around 20' in the air by myself with these crazy angles due to the slope of the roof at 60 years old.

From contributor M:
What you have happening is called truss lift. It is an actual problem. Sometimes, but not always, the problem could be solved with a better airflow into the attic area. A good way to tell if there is an airflow problem would be to look at the shingles on the roof and see if the edges are curled-up a little.

Contributor G is right about nailing the crown to the ceiling. It is what is moving. If you nail it to the wall, then when the ceiling moves up, there will be a large unsightly gap showing where the crown stayed put. Remember to finish the base on the wall before installing the crown or else when it lifts you will see an unfinished line along the meeting areas.

From contributor L:
If your drywall was cracking at the corners it means the drywall wasn't installed correctly, and the framing might be a problem also. Interior partition walls need to be installed with truss clips that allow the truss to move up and down, and drywall isn't supposed to be attached to the ceiling trusses within 16" of the wall- it should "float" to the corner. If it had been installed correctly the drywall would flex, rather than cracking or breaking.

Why is that important? Because crown will not stop the corner from cracking, and once it has cracked you lose your assembly integrity for heating/cooling, and also the fire rating of the material. If you have a fire that crack can act like a chimney, accelerating and increasing the intensity of the fire, and allowing fire to spread easier into the roof assembly. So, if it has cracked you might look into fixing the problem before covering it up with crown.