I am working on an addition with plans supplied by the owner. The plans called for a two story walk out bay window. Because of an additional 6″ bump out behind the bay the total projection is about 30″. The first floor is doug fir 2×8 12″ O.C. cantilevered under the bay. The second floor joists are perpendicular to the first floor and add very little load. The bay has about an 8′ total width. Today I noticed that the bay seems to have sagged just a bit (less than a 1/4″ in 30″) and Im concerned about it getting worse. Unfortunately I wasn’t paying close attention to it when we were framing but now realize that the majority of the load is on the outside corners of the bay. I am thinking about ripping LVL’s down to 7-1/4″ and sistering them to the joists on the outside corners after jacking up the bay.
Any thoughts?
Replies
In addition to adding the supports under the bay I would also look at the roof structure to see if there is any way to help hold the weight. By using braces tied to the structure, along with metal straps to help hold everthing together you may be able to take up some of the weight. I would also nail plywood to any solid areas on the sides of the bay (areas without windows). Perhaps if you jack up the bay a quarter inch or so higer than needed before starting your work, it may settle back down to level after the temporary supports are removed.
Devon Allred
That might help.
The framing palns provided by the owner are woefully inadequate. The cantilever for 2x8 should be np more than 16". Since you have them at 12" OC you gain a little maybe, but that is still just the rule of thumb for single storys. Add the second floor and it should have been cantilevered also.
I would consider using the LVLs at each joist sistered and using hardware to attach to the rim jopist or doubling the joist at each corner with two LVLs.
And in the future, check on the engineering before driving the nails. It helps you sleep better at night.
Thanks for the input. This detail did nag at me a bit but I lost my focus because of some other problems the framing crew and customer were giving me at the time. I am a one man show and sub out the large framing jobs on my remodels. For the smaller ones I have another contractor like myself and we help each other out a lot. This framer, who i have used for years really gave me the short end of the stick on this occasion. He started a new lead man on my job and left him with a couple of well meaning, but still a little green, kids and an older "all he was good for" cut man. Well the new lead guy left a lot to be desired and I ended up having to watch the job like a hawk just to get it square and plumb. I chewed out the framer and found out he was having some difficulties of his own that kept him away from the job. Which I'm sure were true, like I said I have known him for quite awhile. Anyway one of the green kids was actually a pretty good roofer and the framer threw in the roof for nothing and even took some off the bill for aggravation. He took care of all the problems and the final product was very close to his usual work.
I hear what your saying but there really isn't much weight on those lower joists. It's just the bay walls, windows, 20 sq. ft of cantelevered first floor, 20 sq.ft of second floor, and the bay roof. After looking at it a little closer I actually think that it's not so much of a sag as it is the crown of the joists. I am still going to try to straighten it out and beef up the framing. I'm just going to have to buy or rent or borrow a right angle drill to bolt the microlams to the joists.