Identifying Joist Species - Building & Construction - DIY Chatroom Home Improvement Forum


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

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 04-20-2010, 11:26 AM   #1
Member
 
Join Date: Jan 2008
Location: Connecticut, US
Posts: 253
Rewards Points: 250
Default

identifying joist species


The joist span tables I look at say you must know the species of wood to be able to calculate spanning properties correctly. Is there an easy way of identifying the species on 50 year old joists? Do I need to get a sample tested someplace, or are there any tricks to do it in the field?

Advertisement

tpagel is offline   Reply With Quote
Old 04-20-2010, 12:53 PM   #2
Mod
 
kwikfishron's Avatar
 
Join Date: Mar 2010
Location: Kansas (NCK)
Posts: 7,831
Rewards Points: 2,498
Default

identifying joist species


What part of the country are you in?

Can you post a picture of the wood?

Advertisement

__________________
A Picture Is Worth A Thousand Words
Especially In The DIY Chatroom
kwikfishron is online now   Reply With Quote
Old 04-20-2010, 01:06 PM   #3
Member
 
Join Date: Jan 2008
Location: Connecticut, US
Posts: 253
Rewards Points: 250
Default

identifying joist species


I am in Connecticut. Can't post a photo as I have not exposed the joists yet. This is my "next" project and i am trying to think ahead. Will post photos as soon as I am able. Thanks for your reply. Can you take a "guess" (I won't hold you to it) based on the region I live in?
tpagel is offline   Reply With Quote
Old 04-20-2010, 01:50 PM   #4
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

identifying joist species


Quote:
Originally Posted by tpagel View Post
Is there an easy way of identifying the species on 50 year old joists? Do I need to get a sample tested someplace, or are there any tricks to do it in the field?

To get the modulus, E, support an on-edge joist at each end, step in the middle, then post midspan deflection, total span, joist actual dims and your weight.
The violin makers say that old wood gets stiffer, so the E would increase.

Alternately, slice off a small piece with the grain, near the end of a joist [the IRC has rules for this] and do the same experiment with a lighter weight.

These values can be used to calculate the inputs for this link,
http://www.efunda.com/formulae/solid...ple_centerload
or it can be done with a hand calc. or on a spreadsheet, using the link formula for Wmax and solving for E.

I = [1/12] bh³ where b is the beam edge width and h is the height.
and
w = PL³/48EI so E = PL³/48Iw

Knowing E, you don't need to know what type of material it is, be it wood, steel, copper, concrete. . .

Last edited by Yoyizit; 04-21-2010 at 04:29 PM.
Yoyizit is offline   Reply With Quote
Old 04-20-2010, 04:25 PM   #5
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

identifying joist species


What are you trying to do ?
Scuba_Dave is offline   Reply With Quote
Old 04-20-2010, 04:51 PM   #6
Member
 
Join Date: Jan 2008
Location: Connecticut, US
Posts: 253
Rewards Points: 250
Default

identifying joist species


Trying to decide whether I will need to sister the joists below if I build out an attic level into living space. Right now, there are 2x8 joists at 12" O.C. spanning about 16'-3". I "think" that this may not be up to code, so I was going to take out the living room ceiling and sister all the joists with 2x8's glued and nailed with 3" nails about about 6" on center. I was going to have to take out the living room ceiling anyway for another reason, so that's not such a big deal, and it will also let me add acoustic insulation between the levels. I need to do the span calculation to know whether I really do need to sister the joists. What do you think? 2x8's? 12" OC? Good enough or needing support?
tpagel is offline   Reply With Quote
Old 04-20-2010, 05:02 PM   #7
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

identifying joist species


2x8 hem fir #2 grade 12" OC will span ~15' 7" 30psf
#1 gets you to 15' 10"
2x10's #2 grade will get you the span you need

Or add a support beam in the middle

Advertisement

Scuba_Dave is offline   Reply With Quote
Reply


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
Space between joist and beam on deck schveiguy Building & Construction 11 09-08-2009 10:15 AM
one rotted deck joist to replace, need advice dougq Building & Construction 10 07-07-2009 03:18 PM
floor joist issue drtbk4ever Building & Construction 4 03-22-2009 11:20 AM
replacing rotted sill plate and rim joist behind a deck ledger board tommyt Building & Construction 2 08-11-2008 08:38 PM
Cutting/drilling hole in joist - How big? curls00 Carpentry 3 07-20-2007 10:56 PM




Top of Page | View New Posts