design question for John

Started by Mia, January 24, 2005, 01:03:33 AM

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Mia

why is the 2 story cottage only 20 feet wide, instead of, say, 24 feet wide?  24 feet wide would make the room arrangement much easier for me, especially upstairs.
I know that we could make it longer.  I have already drawn floor plans using 38 feet instead of 34 feet.  but why not wider instead?
I suppose that we would have to use the post-&-beam method if the house were wider than 20 feet.  that's o.k.
thanks.

jraabe

#1
There is absolutely no reason the house couldn't be made 24' wide. It is fairly simple changes but the elevations, the joists, and the beams all need to change.

This was the last house in the 20' wide series. 20' is the widest a house can be made with common joists spanning the full width (I-joists can span further). This house also has an optional floor system with internal beams and posts which all wider houses will need to have as well.

Just trying to keep it simple.

My own house is 24' wide and that will be the next series.


Jimmy_Cason

#2
I will be using the 20' Wide 2 story plans.

 I want to add several windows (approx.)  24"wide x 48"high placed in both upstairs and downstairs.

And I want to add a giant window next to the front entry door,  (approx) 60"wide x 48"high.

Because all of the exterior walls are the only load bearing walls in the structure,
Do I need to be careful of adding windows to the design?



jraabe

#3
If you are in hurricane or earthquake areas you will want to have a section of solid wall sheathed with OSB or plywood near the corners. This will provide shear panels and "lock the corners" of the building against racking.

In other words you don't want to run a long bank of windows right into the corners from either side.

To be conservative have a 4' wide panel on each side of the corner and at least every 25' on a long wall. For two stories you need more beef on the lower floor. See braced wall panels: http://www.iccswwc.org/documents/26.pdf

You can also do an alternative braced panel and get the width down to 2'-8". See detail:http://www.iccswwc.org/documents/R602.10.6AltBracedwallpanel.pdf.

Now, this is for WA state where we expect the big one any day. (A SE Asia type underwater earthquake happened about 200 miles off the coast in 1700 that caused a large wave that killed many people in Japan - no historians were here then, but in some places the land dropped 6' and entire villages were wiped out.)

Check what is needed locally for wind and earthquake — the need for such bracing varies a lot. The plan, as drawn, tries to meet the braced wall requirement but this will not be needed in most places.

JoJoD

Please clarify - if I change the dimensions to 24 X 30 - can it still be built using I joists and no interior load bearing walls?


jraabe

You can span the 24' width with I-joists but you need to go to a heavier duty 11 7/8" at 12" o/c or 14" joists at 16".

I would probably do the internal beam system that is also shown in your plans. Then you can just upsize the standard joists to the wider span.

DavidLeBlanc

With respect to these corners, etc, would that be a problem with my idea of having a window seat take up much of the end wall of a 14' wide Builder's Cottage?

Having seen, with my own eyes, what goes on to a corner of a house without adequate beef in the corner (corner of building would bang up and down severely in a brisk wind), I was thinking of little box posts in the corners like 12" x 12" or so... In any case, there wouldn't be enough room on the 14' wall to do a 2'8" alternate with approved hold-down device. Does the structure of the window seat itself count for anything?

jraabe

A cantilevered pop out is basically a hole in the wall structure much the same as a window. If it has a full foundation and tie downs under it, then it can start to be helpful (and will require more sophisticated engineering to calculate).

Remember that the prescriptive path braced wall panel can start anywhere within 8' of the corner.

borgdog

Quote
Remember that the prescriptive path braced wall panel can start anywhere within 8' of the corner.

So does that mean theoretically you could run a 7 foot window right to the corner and start the braced wall panel after that?  


jraabe

That's my understanding of the code.

However, I am not a building inspector and especially not YOUR inspector, so your mileage may vary...