My son is modifying a knee wall on his just purchased first house and I need a little help keeping him out of structural trouble. I am uncomfortable with what he is doing but am not an expert in this area, your input appreciated.
House is a 1960s’s 1 1/2 story with a dutch colonial roof line over the master bedroom where he is working. It’s an odd unequal length roof line where the section from the ridge has a shallow pitch, then joins the section that pitches steeply to the outside wall. The juncture of those two roof lines meets over a full height inside wall that I am calling a knee wall. The ceiling joists, upper roof rafters and lower roof rafters all meet and connect here. Those 3 elements are nailed to each other and the knee wall. The ceiling in this room is flat and at normal height. The original construction of this knee wall is a typical 2×4 16″ O.C., single 2×4 top and bottom plate. this wall is 14′ long. The wall obviously spans over the ceiling joists of the room below, it is about 3′ from outside wall of the house. So this wall is carrying the ceiling load and I think much of the roof load. The lower part of the roof is of 2×4 rafters. It is so steeply pitched that it is really almost qualifies as a wall.
With that as (hopefully) helpful background, here is what he wants to do. Replace this wall with a mostly clear span to further open up the room. Proposed is a double 2×10 with a 1/2″ ply in between supported at both ends with double 2×4’s. Esentially a header that the ceiling and roof structure would rest on. His plan also calls for double 2×4’s about 8′ apart about mid span of that 14′ and a single 2×4 about 3 ‘ from one wall. So its not really a clear 14’ header. He is a seasoned M.E. but not a structural engineer. He says the calculations for the header are good, even overkill according to the guidelines. OK, I am going to buy that for now. But my concern is where does the load go when it hits the floor? Original as-built had a stud over every floor joists carring the load to the outside wall and center house load bearing wall on the first floor. His plan takes the load down to 5 points over 5 floor joists. He does intend to double up the 2×4 bottom plate. I contend that the load is to much for just 5 points. He says the load will distrubute over the floor and the other floor joists will pick up the load.
Some of these dutch gambrel style house don’t even have any “knee walls”, my neighbors house is like that, so maybe there is no huge load that I am worrying about. Or maybe there is. Opinions? Advice?
Thanks,
Ted
Replies
you are correct in wanting to look at where you will be point loading under his design, but what is the point of opening up the wall is he is going to have his new openning broken up like that?
seems conterproductive...BUT its not my bedroom.
mark122
That is exactly a point I have made to my son. Proposed new wall is in the same place as old but with a different configuration that doesn't change much in my mind. A lot of work to get back to the same place. But his plan for that 14' wall has an 8' wide section opened to allow the bed to be pushed back a few feet. The remaining wall space on bothe sides will be builtin shelves and cabinets floor to ceiling. That's why there will be an odd number of studs placed along the wall where there was studs 16' O.C. I have seen such designs like this and they do look nice.
Thanks for your reply,
Ted
What guidelines?
tednh wrote:
He says the calculations for the header are good, even overkill according to the guidelines.
Ted
What guidelines are you referring to?
Reply to deadnuts
I believe he is using a book from Tauton Press on Framing by Pro's for Pro's. I also sent him a PDF of the IRC 20003, that's the code used in his town. He may also being using some other load calculators I am not aware of.
But books and codes need to be interpeted and translated into actionable plans matched to the current structure. There are a couple of ways to get there, 1) an experienced builder who can visualize the loads and instinctively knows whatt the framing will support and what needs to be enhanced, and 2) get a structural engineer to review the plan, change it if required and sign it off.
I have done a lot of remodeling on houses I have owned and am just skilled enough to know what I don't know about load bearing walls or major structural building elements, so not qualified to be #1 above but I can follow a plan and do the work.
I will suggest he takes his ideas past an engineer for review before we procede with the work.
Thank You for your reply, it made me think a moment about how the "engineering" aspect of this plan is unfolding.
Ted
best conclusion
Actually, if your son is making structural changes to his home, then a permit is normally required. That being the case, then your #2 option is really the best (legal) way to "get there"*. So your advice for your son to run his idea's past a structural P.E.is, bottom line, the best advice you can give him.
*other than building to the prescriptive code contained within the 2003 IRC. I would submit, however, that if his framing condition were prescriptively outlined in the IRC, then you wouldn't be asking your original question posted in this forum.