Sistering Joists - Building & Construction - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction


Thread Tools Display Modes
Old 05-03-2007, 02:58 PM   #1
Join Date: May 2007
Location: new jersey
Posts: 1
Rewards Points: 10

sistering joists

i have a full loft above my 20x24' garage. the 1/2" plywood floor is laid on 2x7x20' joists. the span is 16" oc. to what degree would sisterig with 2x12x20's help eliminate the deflection i now have?


tdelc is offline   Reply With Quote
Old 05-03-2007, 03:34 PM   #2
Join Date: Feb 2006
Posts: 334
Rewards Points: 250

I'd like to know where you get 20' lengths from, no way that's what you have and even 20' 2x12s won't give you enough strength in the flex area to do anything with, you need to shorten the unsupported span, or you probably already have strips of wood in the middle of that span up to the roof rafters holding it all up, that's what they did in my garage, I have a 22' unsupported span, but they aren't one piece, they double up in the middle.


R&D Tile is offline   Reply With Quote
Old 05-03-2007, 03:34 PM   #3
JazMan's Avatar
Join Date: Feb 2007
Location: Troy, Michigan
Posts: 5,855
Rewards Points: 412

It would make a tremendous difference. Adding 2x12 Southern Pine in #1 or select structural grade would be adaquete by themselves. Sistering to the 2x8 you now have (1.5x7.25) would be great. But the ends would need to be supported too. If it were me I would sister with the same size you now have making it a much easier job.

Double check the thickness of the plywood subfloor, hopefully its 5/8 and not 1/2". All Plywood measures 1/32" under the stated thickness. What do you plan to use the loft for? Oh, the span is 20 ft. not 16".

JazMan is offline   Reply With Quote
Old 05-03-2007, 06:13 PM   #4
Home Improvement Guy
ron schenker's Avatar
Join Date: Jan 2006
Location: ontario, canada
Posts: 351
Rewards Points: 250

Remember to use construction adhesive when you sister and some bolts and nuts wouldn't hurt either
ron schenker is offline   Reply With Quote
Old 05-05-2007, 06:57 AM   #5
Extreme DIY'r Adk's, NY
Join Date: Nov 2005
Posts: 324
Rewards Points: 272

[quote=R&D Tile;43410]I'd like to know where you get 20' lengths from, quote]

why? I assume he means 2x8's but I can even get 2x6's in 20' lengths?
crecore is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
garage ceiling joists josh123 Carpentry 6 07-14-2009 11:07 PM
sistering 2x6 ceiling joists nelsonC Building & Construction 23 11-21-2008 10:01 AM
Floor joists for 2nd Floor Addition poptop Building & Construction 4 01-11-2008 07:57 PM
3/4" hardwood, same direction as joists? zel Flooring 13 05-15-2007 08:50 PM
Spacing of ceiling joists Pineconeman Building & Construction 3 05-13-2005 11:16 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1