Framing: load-bearing or not?

[Ben Brewcat]

I'm re-framing a portion of a wall on my aged, many-times added-onto single-story house to put in a modern 6X5 window instead of several single-pane oldies. Now bear with me: this wall (of a small sunroom) is perpendicular to the joists and rafters on this section of roof, and three feet inside is another wall that's sided and insulated like an exterior wall. The inside wall is right where the joists end (nailed to the rafters) and then the rafters continue out to rest on the plate that tops this exterior wall that I'm going to be working on.

Question: is this a load-bearing wall? The framing doesn't clarify much; two doubled 2X4s support a ten-foot 4X4 header all the way across; the interior wall (under the joists) has a single 2X4 between a sliding glass door and a window for that same span (yikes).
SWMBO wants to get rid of the inner wall. Seems like you couldn't safely just let the joists cling to the rafters unsupported, but there isn't much there now except that 2X4 holding up a header... obviously I'm not an engineer or a framer.


Is the wall under the joists or the wall under the end of the rafters usually the load-bearing wall?

[Hillside]

As someone who has an old house that has been redone several times, I would say that the interior wall sounds like the origional load bearing wall. If you want to get rid of the wall, you will have to leave a header to hold up the roof. But it's really hard to know without seeing it.

I hope the sliding door and the window have headers above them. A single 4 x 4 doesn't sound like much of a header, but we can get some pretty dramatic show loads here, so houses in my neck of the woods tend to be over built.

You might get a hint of whats going on by looking at the basement. Is there a load bearing wall (or beam) under the interior or exterior wall?

Someone with a little building experience could look at it and tell you.

[Will]

An easy assumption is both walls are load bearing. One wall is bearing the roof load. The interior wall is bearing the ceiling load. Most of the time rafters and joists bear on the same wall when talking about exterior walls. 2x4 headers are only sufficient in interior non-loadbearing partition walls. Load bearing headers should be made of 2x10, 2x12, or engineered lumber. I would suggest a trip to the library for an appropriate book on framing or remodeling. Television shows are notorious for making things look alot easier than they actually are. And now for the disclaimer: All building codes and construction standards apply. If you don't know what those are, I wouldn't attempt the job.

Will

[tecumseh]

ben sezs:
Is the wall under the joists or the wall under the end of the rafters usually the load-bearing wall?
tecumseh adds his 2 cents:
as Will has suggested most wall hold up something and tecumseh would suggest that just about any structure can be retrofit to current needs.
the process is not that complex. since you are dealing with a single story structure the complexity is greatly reduced. figure out how much load the roof must support (likely 40#/sq foot plus snow load). count the size and spacing and span of rafters and consult a load table to see just how much you existing stucture was designed to hold up. if the wall that is to be removed is fairly long you will likely have to build in a beam to carry this load. engineer lumber or fitch beam (2 pieces of dimensional lumber with glued plywood or bolted metal sandwiched between) is generally how I reconstruct load bearing structure.

The distances between load bearing wall (how big are the rooms) is normally the parameter of greatest concern.

wish you luck..

[Ben Brewcat]

Both of these walls sit on a thick (three plus feet) slab of concrete. I can't get under there at all, but the sole plate sits on that slab. Since we're talking 10 rafters/joists on 24" centers for this section of roof, and only half that for the modification, I'm kinda hoping that if I build a sturdy header and jack the rafters/joists while working I should be in good shape. When in doubt overbuild (we do get occasional heavy, wet snows): anything wrong with just going big?

[Michael Bush]

>The inside wall is right where the joists end (nailed to the rafters) and then the rafters continue out to rest on the plate that tops this exterior wall that I'm going to be working on.

Sounds like a load bearing wall. Ask the local building inspector what the requirements for the header are and then you won't waste your money and time on something that won't meet code.

[tecumseh]

ben adds:
When in doubt overbuild (we do get occasional heavy, wet snows): anything wrong with just going big?

tecumseh replies:
it is nearly impossible to overbuild a project unless you are talking about budget. beam constructed of dimensional lumber, plywood, glue and screws will hold up large loads and if you substitute metal and bolts for the plywood, glue and screw you can easily support extremely heavy loads.

your basic description sounds like an added on space that could possible have once been a porch. the fact that a concrete bean lies directly beneath both walls suggest they are both load bearing. if it is an old porch that has been enclosed then you need to be a bit careful with the interior wall (at one time the exterior wall), which would definitely make it load bearing. if this is the case and you still desire to remove the wall, then you will need to shore up (just like shoring up a roof of a mine) on both sides of the wall before it is removed. another concern is the rafter set at 2' spacing, which is pretty much standard in a garage but not so bueno in a resident (especially with snow loading).

what is the basic dimension (length and width) of the interior room in question?

[Ben Brewcat]

Ten feet wide (across the rafters), three feet deep (joist end to just shy of rafter end; they project @ eight inches outside). This same section of roof, supported twice with knee-wall looking braces that rest on 1) an old roof underneath and 2) the ceiling joists, continues an additional 10 feet next to the section I'm working on, divided by an interior wall (creating another funny three-foot by 10-foot room that currently houses the back of a fireplace next to my little sunroom). I think you're right about the patio/porch thing; that's the only use for this setup I can think of.

[tecumseh]

It still might be an excellent idea to go by a used book store and look up a copy of a paperback book called "Pole Building Construction". There are a number of load tables in the books center that with a small bit of reflection should give you a pretty good horse back estimate to convert span and load to dimension lumber (2x4, 2x6,etc). If the room is 10 foot wide and about the same depth then even with limited construction skill the project should be doable. The real problem comes when span approach 20 feet and all you have is traditional dimensional lumber to implement the modification.

and another possibility... if your attic has working space you can resupport in the attic via a device called a strong back. which is simply large dimensional lumber (normally 2x10's or 12's) fastened together (I prefer screw to nail) to form and L. the verticle part of the L must span from sidewall to sidewall and the horizontal part of the L is the member used to attach to the roof joist.