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-   -   How to frame new floor to match existing floor height (http://www.diychatroom.com/f14/how-frame-new-floor-match-existing-floor-height-68303/)

taylor01 04-04-2010 04:52 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 05:19 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 07:06 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: http://arch.umd.edu/Tech/Structural_..._Guide_A11.pdf

When you notch, drill a relief hole so as not to start a split there: http://www.finehomebuilding.com/PDF/Free/021184090.pdf

Be safe, Gary

taylor01 04-04-2010 08:02 PM

Gary,
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 08:59 PM

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

Be safe, Gary


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