What makes a roof bow like this? - InspectionNews

rob martinez · #1 (**permalink**) 06-05-2007, 11:16 AM

I need some help with explaining why a roof may do this. Unfortunatly I had no access to the attic in this area. It was right at where the garage meets the house. Bowed up in this one area. Thanks for any help!

Jerry Peck · #2 (**permalink**) 06-05-2007, 01:16 PM

Poor framing, but, as you live in CA, maybe earthquake?

See any cracks anyplace?

Chip O'Brian · #3 (**permalink**) 06-05-2007, 01:56 PM

Any possiblity of truss up lift?

Bruce Breedlove · #4 (**permalink**) 06-05-2007, 04:10 PM

Movement associated with truss uplift is most noticeable along the bottom chord of a truss, especially where the ceiling meets an interior wall. Truss uplift would cause only negligible movement along the top chords of a truss.

Bill Wieczorek · #5 (**permalink**) 07-20-2007, 08:35 PM

I hope someone has an answer. My 25 YO home looks like that in 5 different areas of the hip roof and I can't see a thing wrong from the attic area.

Gunnar Alquist · #6 (**permalink**) 07-20-2007, 09:59 PM

Rob,

Looks like this is several days short. I guess Bill resurrected this, but I might as well attempt an answer.

There are a few possibilities.

One is that the the roof is not bowed up, but sagging on either side. The wall between the garage and house will often hold up the roof framing while the stuff in the attic and above the garage sags. Garage roofs in my area are notorious for sagging due to undersized rafters and if the room on the other side of the wall is the living room it is likely that it too has an unsupported span. If the house was built in the '50s or '60s there is a good chance that the rafters and/or purlins are 2x4s. Quite often, the ridge is 1x6 as well. I am not terribly far west of you and this was standard framing around here during that time. Probably there as well.

Another possibility is expansive soils. The wall between the garage and house could have heaved upward causing the hump. Since you are in the flats of the valley, I would expect expansive/adobe soils.

Both are possibilities in the Sac area. If I were to place a bet, I would go with door #1.

Jon Randolph · #7 (**permalink**) 07-20-2007, 10:53 PM

What does your foundation/sill plate look like? Any cracking on the interior walls? Do your doors close or hit the casing?

Matt Fellman · #8 (**permalink**) 07-21-2007, 11:40 AM

If/when I can't really explain why something is the way it is I resort back to what attorneys and experienced inspectors say.... write what you see. Of course you dress it up a bit more than just saying the roof has slopes. It's nice to always be able to explain what caused something but as you can see there's several possibilities. Nobody can argue with what you see.

Bill Wieczorek · #9 (**permalink**) 07-21-2007, 07:43 PM

Jon I don't know if your speaking to me, I'll butt in if you weren't. I have an all brick veneer home with a 10 inch foundation. Been in it Four years, its about 25 YO home. There were 2 areas where hydralic cement was used to patch some leaks that happened in the first year according to the original owner, no other cracks. Our soil is mostly clay with some topsoil not fun to dig in. Truss roof, 2x4 24 inch centers with plywood sheeting. When I moved in I didn't notice the rises in the various areas so it seems there getting worse. There was a new roof put on a year before I purchased the home. I posted this question 15 months ago hoping someone could answer it with a definative answer but no luck. Thanks for your input though.

James Duffin · #10 (**permalink**) 07-21-2007, 08:35 PM

Just curious...how deep was the garage measured from the garage door to the back of the garage? I am assuming the bow is in the garage roof.

Jon Randolph · #11 (**permalink**) 07-21-2007, 10:22 PM

Bill,

What about the garage floor, any large cracks or uneveness?

By your last comments I assume that you are on a basement, and all of the foundation walls are visible?

Was the entire home and garage built at the same time or was there additions? The way that the valleys come together at the point where the drop appears to begin makes it look like that has been some adding on in the past. Maybe by a DIY homeowner that made miscalculations during construction.

Is the entire roof trusses?
Are all of the trusses still attached firmly at the gussets?
What about rafter spread (if any are present)?
Am I seeing a hump in the middle of the ridge or does one end drop down? It's hard to tell from the pics, but it looks like it drops down at the garage wall.

Bill Wieczorek · #12 (**permalink**) 07-22-2007, 08:01 AM

Jon this picture isn't of my home, that's from the original poster. I don't have a picture. Yes, everything was built at the same time, no DIY project here, yes I have a full basement. I can't see any rafter spread. I haven't walked the entire attic space but the areas I can get to where the problem is occurring look OK to me. The tress's look fine and yes attached at the gussets.

The guy behind me just had a roof put on. I talked to to the guy doing to work who said he'd take a look but never stopped by. His opinion without seeing it was possibly the plywood is warping from lack of ventilation. I doubt that I have a continuous soffit vent all around the house with another 10 roof vents. I've been up there on a windy day and it's almost as windy in the attic as it is outside. Great Ventilation.

Jon Randolph · #13 (**permalink**) 07-24-2007, 08:59 AM

The house in your picture, if there is not any rafter/truss issues, shows some serious signs of settlement. I would recommend a structural engineer and possibly a soils engineer depending on the SE's findings. There is no way that this is warped decking.

Gunnar Alquist · #14 (**permalink**) 07-24-2007, 11:07 AM

Bill,

I would help us if you filled out the rest of your personal information. Knowing where you are would give those that know your area more information.

Gary Schutta · #15 (**permalink**) 07-24-2007, 08:44 PM

Well appears home & garage are on two different foundations where the garage has settled differently than the home. Check permit history for possible addition.

Gary

Randy Aldering · #16 (**permalink**) 07-27-2007, 09:40 AM

What does the framing look like in the attic? How many layers of shingle are on the roof? Has the roof ever had tile?