Sill Plate Overhang

[stickmotion]

I have had various contractors contact me about overhanging the sill plate of a 2x6 wall 1.5 inches beyond the foundation to flush out the wall framing with the rigid insulation for the foundation. I have seen references for allowable overhangs of 1/3 the wall thickness and 1/2 the thickness of the plate. Are there code references for either of these conditions or are they simply rules of thumb used out in the field.

Any feedback is appreciated.

 

[SLTA]

Do a bending analysis on the plate and you'll find it's fine. Of course, having super-heavy facade materials would be a bigger issue for a larger overhang. If you're concerned, go with a double sill plate.

Please remember: we're not all guys!

 

[XR250]

I have never thought it to be an issue with a 2x6 wall. Any reasonable axial load will find its way to the 3 1/2" of bearing.

 

[msquared48]

However, never hang a joist in a metal joist hanger off a cantilevered plate.

Mike McCann, PE, SE (WA)

 

[KootK]

Do a bending analysis on the plate and you'll find it's fine.

Is it not flexural tension perpendicular to grain? I thought the capacity of that was zero.

As I see it, the rational treatment is to treat the overhang as if it didn't exist. Stud bearing lengths get reduced and studs get loaded eccentrically from the bottom.

If I remember correctly, Wisconsin's res code explicitly allows 1.5".

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[OldBldgGuy]

Ontario's code allows 1/3 the width of the plate without analysis. If you're going to analyze it & take responsibility for it, you can do whatever works.

 

[dhengr]

Stickmotion:
Look at it this way, with a 2" overhang, you still have an equivalent 2x4 sill pl. and stud bearing on the wall, and this is usually adequate for most vert. loads and lateral load bending, no cross grain bending analysis of the sill pl. is needed. And, compression perpendicular to the grain on the 2x4 sill usually controls this part of the design. That’s a good detail, a common detail, the 2x6 wall is usually there to get enough insulation on the wall and it does provide a good stiff wall. Otherwise, it just takes a little engineering judgement and a set of balls to justify it, not 17 pages of codified crap. And, any AHJ who would not accept this is just as dumb as a rock.

 

[OldBldgGuy]

Funny thing is, everyone seems to have forgotten why we build with 2x6. dhengr is right, in the vast majority of instances it is strictly an insulation holder.

 

[Ron]

Check the plate anchorage. Overhang usually brings the anchors too close to the edge of the slab to get the rated capacity of the anchor. Contractor usually installs in the center of the plate without regard to where the plate sits in the slab.

Another issue is that overhang exposes the plate to weathering/deterioration.

 

[XR250]

Funny you should mention the bolt issue. In our area, they construct 2x4 walls on the edge of monolithic slabs all the time. There is barely any cover on the side of the anchor. I have been letting it slide in all situations except shearwalls as it is standard practice in my community. I now am recommending that they use 2x6 walls in these situtations to get more cover.
I guess the other option is to use some of those kinked Simpson anchor bolts.

 

[Tmoose]

"kinked Simpson anchor bolts"

http://i.imgur.com/Y89x3aJ.png

?

or,

https://www.strongtie.com/bolts_anchorbolts/sb_bolt/p/sb

 

[stickmotion]

Thank you for all of your feedback!