There are "standard" charts, however I have noticed that a modern 2x8 may be either 1-1/2 inches or 1-5/8 inches, depending on the manufacturer. The width sometimes varies a little also. Best to actually measure your beam to be sure.

 

Most the pressure treated here are 1-5/8 and 1/8" wider because of the treatment when green. You can get kiln-dried-before-treatment which are 1-1/2 after treatment, for more money. Check your plans if a one story room addition on block, you can probably use 2x6 on the 6" block for 2x6 walls, 2x4 plate for 2x4 walls, whichever has been approved on the engineered/stamped plans. http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_6_sec006_par003.htm
Or are you two-story with the 8” block?



Gary

 

The 1/8” your concerned about doesn’t even exist in the eyes of a framer.

 

It does for me. If your doing a foundation for an addition and you have to have the top of the new floor joists even with the top of the existing floor joists, the top of the foundation has to be figured out exact. If you use double sill plate and it's 1/8" difference, that's a 1/4" that the new joists would be sitting above the top of the existing joists. you even have to figure in the thickness of the sill seal.

 

Though he is matching up the floor elevations of new/old. It is a big deal there...... The biggest problem when matching is the existing floor sags in the middle-- follow that slope with the new if only 8' or install level..... but you are correct... a remodel carpenter would/should watch for that, most framers wouldn't- unless adding joist, stud, plates for wall sheathing break point when specified. Or a rake wall tying into a level wall. Or rafters, stairs, or structural blocking. I'm too picky....
PS- don't forget the sill sealer or termite shield if required.

Gary

 

I see it all the time with addition. If I show up at an addition and the siding and sheathing isn't ripped off down to the framing, I know right there that there will be a problem because how can the mason possible get the height right without opening uip the wall. Yiou can't just assume if your using new 2x10's and the existing are 2x10's that you can make the new fouindation the exact same height...doesn't work that way. Mnay old homes a 2x10 can measure 9" or 9-1/8".

Where I'm from conventional lumber 2x10's measure 9-3/8-9-1/2". There is a slight variation and they will shrink. I-joists they are exactly 9-1/2" and don't shrink. You have to figure the height of the new joists, the double plate thickness or single plate and the sill sealer thickness to determine the finished foundation height when match the top of existing floor joists. That is the most important thing.

Alot of times the new joists are taller than the existing joists and I've seen foundations the same height...there begins the problem. You are better of with the foundation being a little lower than higher because you can always add a piece of 1/4"..1/2" piece of plywood to the top of the sills need be.. Being to high you have problems.

 

Well, if we're giving them both barrels..... page 49-52, ; http://books.google.com/books?id=iwSasc7rowcC&pg=PA38&lpg=PA38&dq=heel+or+toe+bearing+with+rafter&source=bl&ots=QXpuP2csh6&sig=aBxUyKfe4mv2pWTq5bQon4cZvj8&hl=en&ei=L8gnTIqtL9CHnQfkk9m8Bg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBIQ6AEwAA#v=onepage&q=heel%20or%20toe%20bearing%20with%20rafter&f=false
Though I wouldn't cut the sub-floor...

http://www.paintsource.net/pages/solutions/new construction/wood_shrink.htm

http://www.buildingscience.com/documents/insights/bsi-023-wood-is-good-but-strange/

Gary

 

Thanks

Thanks for all of your replies.

The new construction will be added to the old house and its walls, floors and joists/headers will be exposed for exact height measurments.

In reply to one post- I have always covered the block foundation with the same size sills. The engineered I joists will lay on the sills and need that space for support.

I guess I could use 2x4 sills where the joist rims on the two other sides are, but have never done that.

 

Termite shield

Just a bit of information- I checked Home depot, Lowes and

Menards for termite shield. Not one carried it.

I guess i could use 10" sheetmetal flashing and bend down the edges later. It would look better if it came with a factory bend thats uniform.