New Floor Joists For 3rd Floor Attic Remodel - Building & Construction - DIY Chatroom Home Improvement Forum

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


Thread Tools Display Modes
Old 11-30-2011, 10:24 AM   #1
Join Date: Jan 2011
Posts: 3
Rewards Points: 10

New Floor Joists for 3rd floor attic remodel

I have a existing 2.5 story with stair access to a 3rd level. This existing attic space has 2x6 @ 16oc floor (2nd floor ceiling). 2nd floor ceiling's are plaster/lathe. I have a large cathedral attic ceiling and installed closed cell spray foam in rafters and want to build an adequate attic floor system to support it. Attic spans are 10'-14'. Two questions:
1.) Can I get by with 2x8's both floated and/or sistered to existing 2x6's or do I need to use 2x10's? With some blocking mid-span my hope is to use 2x8's.
2.) My basement is being updated with steel structure but do i need to be concerned about the 1st/2nd floor wall construction and the additional weight bearing on it?



appleman11 is offline   Reply With Quote
Old 11-30-2011, 11:13 AM   #2
Ole Wood Worker

BigJim's Avatar
Join Date: Sep 2008
Location: Chattanooga, Tennessee
Posts: 10,652
Rewards Points: 800
Blog Entries: 1

2X8s will be fine for a 10 foot span but will be a bit bouncy for 14 foot. If I were installing the joists I would hold the joists up away from the lath and plaster. Fastening the joists to the existing joists will be tricky also as it will be easy to disturb the plaster. You for sure do not want to use a hammer on the joists.

I would be sure to check to see if your walls were able to handle the extra pressure. There is no way we can know that, you may have to call someone in to check that. The added pressure will be on headers, foundations etc.

Being the third floor, some one will sure have their work cut out for them.


New members: Please consider adding your location to your profile.

If you do what you've always done, you'll get what you've always got.

BigJim is online now   Reply With Quote
Old 11-30-2011, 11:25 AM   #3
Residential Designer
AndyGump's Avatar
Join Date: Sep 2010
Location: Orange County CA.
Posts: 1,386
Rewards Points: 688
Send a message via Skype™ to AndyGump

I don't know where you are located but the CBC which is based on the IBC shows that 2 x 8 s 16" O.C. just barely makes the grade if using Douglas fir #2 for a 14' span.
Deflection is an L/360 which should be comfortable enough.
Maybe you should have this drawn up and taken to the local Building Department?

AndyGump is offline   Reply With Quote
Old 11-30-2011, 12:25 PM   #4
Join Date: Jan 2011
Posts: 3
Rewards Points: 10

I had planned to lay either 1x or 2x pressure treated pieces on the existing top plates between the existing 2x6's and rest the 2x8's on them to prevent damage to the plaster. If I were to move to 2x10's that's another 20% in weight and I may not have enough clearance to connect the 2x10's to the top plate as the roof line would interfere. I could chamfer them down I suppose but I may already have to chamfer down the 2x8's in a few areas. I have an engineer and architect on board and have drawings, just looking for more encouragement before I attack this myself.. House was jacked up this morning and new steel posts/beams being installed to help carry the attic weight. Thanks again.
appleman11 is offline   Reply With Quote
Old 11-30-2011, 12:58 PM   #5
Disabled wood vet
titanoman's Avatar
Join Date: Nov 2011
Location: California
Posts: 1,661
Rewards Points: 1,004

Do you doubt the architect/builder that you have? I don't know why you're in a forum. sounds like you got it figured out pretty good.
titanoman is offline   Reply With Quote
Old 11-30-2011, 02:03 PM   #6
Join Date: Sep 2011
Posts: 166
Rewards Points: 150

Yes you have some good ideas. The advice you got from JiJu1943 and Andy is spot on. If you go the 10'0'' span use 2''x8'', or 2''x10'' for 14'0''. You can chamfer the absolute minimum amount to fit the 2''x10'' under the roof space (go between the roof fafters and nail floor joists to roof rafters at edges). This will strengthen both the floor and the cathedral roof.

Fill between floor joists with 4'' batts to improve insulation and reduce noise transmission from attic to 2nd floor. Trust your architect to do the right thing (they carry indemnity insurance as a last resort if something goes pear shape). Finally, don't exceed 1'6'' spacing between joists.

As far as using 4''x1'' spacers (laid flat on studs), that's fine, as long as it doesn't increase the amount you have to chamfer from the ends of the joists.

Regards from Joe in Oz
JoJo-Arch is offline   Reply With Quote
Old 11-30-2011, 02:43 PM   #7
Join Date: Jun 2009
Posts: 54
Rewards Points: 75

Did anyone take into account he would SISTER the existing 2x6?


NASCAR9 is offline   Reply With Quote

attic , floor , joists , span , weight

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
Double Bathroom Remodel coreyandnicole Kitchen & Bath Remodeling 1 03-19-2010 09:59 PM
remodel box for wall fixture DIYGST Electrical 4 01-02-2010 03:21 PM
Remodel - Moving from 200 amp service to 320 amps stevedar Electrical 20 11-29-2009 08:14 PM
To Remodel or Not to Remodel... That is the.. Lety Building & Construction 2 09-08-2008 08:47 PM
Patio Door remodel azguy Remodeling 5 02-27-2008 10:03 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1