I'm trying to install a new utility sink and washer hookup in my garage and am trying to plan how I'm going to run the copper supply lines.
The most direct path I can think of is to notch probably 5 or so studs of an exterior wall to reach the existing drain I'm going to use for the sink.
I know that I can't notch a load bearing 2×4 more than 7/8" but I can't find any guidelines as to how many studs in a row I can safely notch. Is this a question for an engineer? I don't want to go notch crazy but I think 5 or so in a row should be ok? I'm also planning on putting stud shoes on the studs i do notch.
Plumbing – the maximum number of load bearing studs in a row that can be notched
framingplumbing
Related Solutions
Here would be my basic approach (Mechanical Engineer here, Statics TA for 4 semesters):
- For starters, you could figure out the weight of the mattress and box spring plus the weight of two people lying on it (
W). Add in a safety factor (at a minimum 2, ideally a bit more) - remember, an uneven or dynamic loading will apply significantly higher stresses to your frame. - If you assume the weight will be evenly distributed it makes things a whole lot easier.
- Figure out which supports your box spring will be resting on. Does it come in contact with the outer skirt on the sides? If not, divide up the weight of the box spring/mattress/people by the number of cross supports (
n) the entire thing rests on, less 1 (W/(n-1)). For the end cross supports, use half of this loading. - Use the distributed load (or half of it) that you just calculated over the span of each cross support in conjunction with a fixed-fixed cantilever beam equation explained in Figure 23 here.
- Calculate maximum beam stress at the center with
σ=M*c/I(whereM=moment,c=distance from neutral axis, andI=area moment of inertia) and compare to your material (pine? oak? maple?) maximum compressive and tensile strengths. - Apply the reaction forces for the cross piece ends to the sides of the supports running the length of the bed as point loadings. (If you want to get fancy, you can include the moment as well and add a torsional stress to the beam, but I don't think I can explain how to do that very well over the internet.) Use superposition (multiple P forces) and Figure 25 for this one. Repeat calculating maximum stress.
If you end up with not enough of a safety factor for your chosen design, increase the width (vertically) of the side beams. For the center, you could just add another support and recalculate. I don't think fasteners will be the limiting factor here, and calculating/estimating the stress concentration factors in an anisotropic material such as wood is a bear.
Edit: So that's how an engineer would approach this. However, @rachet freak has a very good point that you could save a lot of time by using a proven design. In that case, take a look at Ana White's website. It's got dozens of plans that people have already built with basically just a circular saw and a drill.
If it were me, I'd install a new sanitary tee in the main drain, just above the existing sanitary tee. I'd have the standpipe for the washer come down into a P-trap, and connect the other end to the new tee.
However, you'll have to make sure the standpipe is at least 18" above the trap weir. If that height cannot be maintained, you'll have to move some things around.
I'm also not sure if a proper P-trap will fit in the stud bay, so you'll have to measure to verify. The minimum length of a trap arm is two pipe diameters. So if you're using 2" pipe, that's 4" from trap weir to the sanitary tee.
Then I'd have the trap from the washtub, connect to the existing sanitary tee.
Basically, something like this...
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Best Answer
There is no specific limit on the number of sequential studs, as the 7/8" limit is intended to reduce the potential stresses, however, given the choice, I would rather drill than notch:
2308.9.11 Bored holes. A hole not greater in diameter than 40 percent of the stud width is permitted to be bored in any wood stud. [...]
and
In no case shall the edge of the bored hole be nearer than 5/8 inch (15.9 mm) to the edge of the stud.
So 40% of 3.5 in gives you ~1 3/8" to use, often much more than you need for supply lines.
My concern though, is that you're thinking of notching for a waste line, and notching 7/8" to add a 1 1/2 or 2" drain line is... I'll just say that I'm with @JohnSmith in that I wouldn't bother, but then I don't know your specific situation.