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  1. #1
    Join Date
    Apr 2007
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    Smile Bowed Exterior Garage Walls

    I came across this yesterday at an inspection and I want to get your input as to what may possibly be causing this.

    Here's the situation from the ground up: Cracking and heaving at the garage floor, various cracks noted at interior cinder block including differential settlement, collar ties were put in place to prevent additional ridge sag, bowing of the exterior veneer walls, as well as, masonry cracking at exterior veneer walls.

    The seller had two or three contractors including a masonry contractor and roofer who said that the situation more than likely originated from the roof, not the floor. The masonry contractor said that the collar ties actually keep the walls together and bowing out further.

    Both felt that further bowing was unlikely. I did see one tuckpointed repair that already is appearing to separate. I'm not a contractor, but I feel that their advice is off track and that the floor is the point of origination. I appreciate your experience and comments.

    Thanks,

    Sean

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  2. #2
    Join Date
    Feb 2008
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    Default Re: Bowed Exterior Garage Walls

    I have to agree with the contractor's. From the pictures I see the floor looks normal enough. If those are the only 3 collar ties then it is all wrong.
    Collar ties are generally 4' O.C. and about 2/3 down from the peak. Having them sit on top of the wall does not cause a problem for the wall that I am aware of. Depending on width and snow load having the collar ties at the wall instead of mid run can lead to inward bow of the rafters over time.
    Regardless, 3 collar ties clustered together like that doesn't work. Remember the downward force of the roof pitch is always trying to push the walls out. Without any other lateral support there is nothing to keep the walls from not bowing out.

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  3. #3
    Join Date
    Apr 2007
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    Default Re: Bowed Exterior Garage Walls

    Markus,

    I'm sorry I didn't clarify better, the collar ties were put in after the walls started to bow. Supposedly, they are to prevent the walls from bowing further.


  4. #4

    Default Re: Bowed Exterior Garage Walls

    There is a difference in rafter ties & collar ties, collar ties would be in the upper 3rd every 4 ft, if that is not a structural ridge then rafter ties (bottom 3rd) would be needed.

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  5. #5
    Brandon Chew's Avatar
    Brandon Chew Guest

    Default Re: Bowed Exterior Garage Walls

    The bowing at the top of the side walls was most likely caused by failure of the structural roof framing. The rafter ties that are shown in your photo are an attempt to repair or stop that failure.

    Rafter ties are usually placed at the top plate of the walls (but with proper design can be anywhere within the bottom third of the triangle formed by the rafters and the top plate) and their purpose is to prevent ridge sag and wall spread.

    Collar ties are placed in the upper third of the triangle formed by the rafters and the top of the side wall and their purpose is to hold the rafters together at the ridge to resist uplift forces that want to pull the ridge apart.

    As you noted, there may be more structural problems here than just the roof framing. Differential settling is an indication of foundation failure, and this is unrelated to the wall spread. Also, the photos of the lintel at either side of the garage door look like the bricks supporting the lintel have dropped down. This could be due to improper support of the brick down at the foundation. From your photos, I can't really get a feel for how serious these issues may or may not be.

    Structural repairs should have been engineered. Have your client require the seller to produce the engineering documentation on the repairs. If the repairs were not engineered, then last man in (that's you!) holds the liability bag, unless you do what's in the next paragraph.

    Determining the cause of structural failure and evaluating the effectiveness of structural repairs is beyond the scope of a home inspection and outside the skill set of most home inspectors. Recommend that your client hire a licensed Professional Engineer, with training and experience in residential foundation and wood structural framing design and repair, to come out on a consultation and advise them how to proceed from here.

    If this garage was built at the same time and by the same builder as the house, it makes me wonder about the structural adequacy of the house.

    Last edited by Brandon Chew; 04-19-2008 at 09:23 AM. Reason: spell check

  6. #6
    Join Date
    Feb 2008
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    Chicago IL
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    Default Re: Bowed Exterior Garage Walls

    Sorry, you are correct. I didn't give enough time/thought to explaining rafter/collar ties.

    www.aic-chicago.com
    773/844-4AIC
    "The Code is not a ceiling to reach but a floor to work up from"

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