Questions on windows in cripple wall

[Wayne Whitney]

Hello,

When I had my foundation replaced, I had part of the crawl space excavated into a basement. So I'd like to add some windows to the

3.5' - 4' high cripple walls; the house is one story wood frame construction with a hipped roof. A few questions about maximizing the window area:

1) Is there any reason not to set the window sill right on top of the mudsill? I'm aware of the need for any wood to be 6" above grade, of the need to clear any anchor bolts, and the need to level the sill, but are there any other reasons?

2) Where the floor joists are parallel to the cripple wall, can the window go all the way up to the top plate of the cripple wall? It seems that when the floor joists are perpendicular to the wall, a header below the top plate is required to spread the floor joist load. But otherwise, if the rim joist is larger than the required header for the opening, can I rely on the rim joist to spread the load from the wall above?

I will be getting permits and inspections, but as always I like to think things through before submitting plans.

Thanks, Wayne

[Goedjn]

Not that *I* know of, anyway. You want to keep water and bugs away.

Yes, you should be able to go all the way up, but no, you shouldn't depend on the rim-joist by itself. You can double or triple it, depending on how big a span you're talking about, so that you've got a good hefty beam across the top. This doesn't sacrifice headroom, though it may interfere with wireing and/or piping against the rim-board.

[Wayne Whitney]

For argument's sake, if the window is directly below a 1st story window with an adequate header, could one depend on the rim joist? Seems like there would be no loads from the floor system, and loads from above would already be spread.

Also, can a window in a cripple wall span a step in the foundation? Or is that forbidden for some reason?

Thanks, Wayne

[Goedjn]

You probably COULD, but I wouldn't, since the header isn't a significant fraction of the total cost. I don't know what code requires, or what the local inspector (if any) is going to allow.

An architect or engineer can do that sort of situational modification, but a DIYer ought to stick to the canned formula.