I’ve found some references to truss uplift and wondering if my house is experiencing the same. Outer walls are 25cm wide hollow brick walls with steel reinforced concrete columns and there is also a “belt” on top of the exterior walls from reinforced concrete. Interior walls are 12.5cm wide hollow brick walls, without reinforcment. The roof is like this: the long beams sit on the reinf concrete belt around the exterior walls, rafter ties for each rafter just below the longitudinal beam at the top, no horizontal truss, but 2 points (foot) where it sits on top of the interior walls.
it’s unvented with closed cell foam insulation. We live in Romania, so winter is -20 Celsius, summer is 38 Celsius.
On the 1st floor we noticed longitudinal cracks at the height equal of a brick. Then I’ve noticed gaps between the door frame/mouldings and the slab.
The slab didn’t sag, that was checked and measured. And then I came across this pdf from Joe Lstiburek and saw similar picture, thus I’m here.
I suspect something similar happened and the top chords expanded, somehow lifting the interior walls although I do not have horizontal trusses and the roof sits on two poles/feet.
So,
Did the outer walls bend outside and pull up the inner wall pictured
Did the roof lift up and pull up the interior wall from the two feet where it sits
And the image which got me going in the truss uplift topic. My door frame looks the same way and have also those cracks along the gipsum ceiling and wall meetings.
rcloyd
(Russell Cloyd, KY LIC #166164, IN LIC#HI02300068)
6
Looks like it might be due to rafter spread. Can happen when ceiling joists are run perpendicular to the rafters (as shown in your pics) and no collar ties are used at the mid span of the rafters.
If your thermal barrier is at the flat ceiling and not the vault, if your ceiling joists are buried in insulation so you have a flat ceiling with no exposed overhead “beams”, if the attic is ventilated to the outside and is cold in winter, and if you keep that building heated year round, you might have truss uplift. Looks like you have a king post every 3 or 4 trusses, so truss uplift is less likely. Truss uplift occurs at center walls, not outer walls.
Evening, Gyula. Pleasure to meet you. Welcome to the InterNACHI forum.
Those are rafters, if I am not mistaken not trusses.
The rafter beam is being supported by what I call collar ties and notched into the rafter from below.
I can not make out king posts or struts.
Either or, I highly doubt there is truss uplift seeing there are no trusses.
That is structural masonry building. The poured concrete columns almost look like wall pilasters for the wall assembly with hollow Terracotta Masonry Units in-fill.
What is below the slab? In other words, what structural components are supporting the residence?
Is there a crawlspace or a basement?
Are the columns and beams under the main floor supporting the flooring assembly?
Looking forward to your answer.
The attic is not ventilated and it’s insulated with spray foam between the rafters. The cracks I’ve posted are at center walls exactly on which the king post is.
Thanks Robert! The cracks appeared on the 1st floor (2nd story), the roof structural photo is from a different part of the house since I don’t have a picture from the 2nd story roof now, but it’s the same idea. There are 2 king posts which are residing exactly on the walls which lifted upwards (or moved). The slab between 1st and 2nd floor is a hollow Terracota units reinforced with steel (it’s called LEP here) and two horizontal reinforced concrete beams. None of this sagged, we measured it from below and there are no cracks on the ceiling below (the ceiling is only painted, so cracks would be visible immediately)
Ok, here is the structural plan where you can see with orange the int walls, with purple where the horizontal cracks appeared and blue where the roof posts sit on the interior walls.
You can see that the horizontal 25x35cm reinforced concrete beam runs exactly below the orange wall where the door frame lifter (next picture)
And the door/wall lifted. This corner is exactly below the kingpost (or post) and the horizontal cracks start 80cm from the corner because, I think, there are L shaped rebars between the Terracota bricks in the corner which are 80cm long.
So, either we have some uplift and the posts somehow pull-up the wall OR the entire roof sagged, it’s pushing down on the interior walls (which are not reinforced). They can’t compress, so the downward force transformed into a side force, inclining, bending the walls. The corner lifted because it’s held together by the L shaped rebars.
Another consideration for you to exclude. The floor may be pulling down and the walls are hanging onto the roof structure. This is an interesting post, please update regularly.
If the floor is pulling down, it should be visible from the underside, not? And it’s perfectly flat, no cracks or bulge in the ceiling on the ground level since moving in (btw, house is 3 years old).
