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taylor01 04-04-2010 05:52 PM

How to frame new floor to match existing floor height
I am framing an addition over an existing garage. The current ceiling joists are 2x6 on top of a girder. The span is 22' (11' on each side of girder) supported in the middle with a girder made up of 3 2x8's. The existing 2nd floor on the house already goes over 1/2 of the garage and is built with 2x8's spanning the same 22' with the 3 2x8 girder supporting in the middle. I am just adding the addition the other 1/2 of the garage. Now, the plans drawn by a draftsman calls for the new floor to use 9 1/2 gpi's to be used for the new floor. This is not going to work as the new floor height would not match the existing floor height. The only was I see it working is to sister 2x8's to the existiing ceiling joisting making them floor joists. Also I assume I would have to rip down the new 2/8's to match the existing old 2x8's that actually measure 7 inches. Any one see any other options to make the new floor height match the old floor height?

kwikfishron 04-04-2010 06:19 PM

Without a picture and the drafters drawing I can only guess but if there is a difference in joist height from the old to the new then you make the floor right and have the offset in the ceiling below.

Gary in WA 04-04-2010 08:06 PM

Kwikron is right on.... you can end notch a 7-1/4" by 1-7/8" to a 5-3/8" only at the ends:

When you notch, drill a relief hole so as not to start a split there:

Be safe, Gary

taylor01 04-04-2010 09:02 PM

When you speak of notching a 7-1/4" by 1-7/8" to a 5-3/8". Is that dimensional lumber, a 2x8?
Thanks for the great info!

Gary in WA 04-04-2010 09:59 PM

Yes, only solid wood, as the information stated. Never engineered lumber with different rules.

Be safe, Gary

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