Determining grade of joist wood?

I have 2x8 joists, 12 feet long span, in a circa 1959-60 house construction... In determining maximum spans (or rather, weight capacities), how can I find out the 'grade' of the joists? Is there a visual method for this, as I can't really see any markings on the joists (faded?)? With #2, #1, and select structural, from the span charts, I'd be good to go with using 2 sheets of 5/8" sheet-rock in between the joists attached to the above floor. Seriously looking into Green Glue too (?) thanx, K

I guess no one knows how this would be done visually? K

Hey leftweg, I've been thinking about this question, did some searching & asking... since you bumped it... The only thing I found (and sorry I'm in a rush, don't have time to refind and post link) is that you can have a sample of the wood tested by a lab to determine species. Other wise you should presume (or atleast I would)it's #2 grade or better... most #2 grade wood seems to have similiar load weights so you may be able to do some guestimates while you wait. Other option is ask your neighbors or seek down some carpenters, architects, contractors or other "pros" who have worked on renovations to houses in your area and ask them. That's how I found out what species my trusses are made of. Other thing's to mention and I'm not a pro, I've not seen (yet) anything other than a 2x4 rated as #3.... every other larger peice of lumber seems to be #2 or better. Most floors/cielings seem to have a 10PSF rating min, with some rooms 20PSF.... but that is current code and may not apply to older houses. Hope this helps a bit.... but remember I'm not a pro and the end recomandation especially for your ceiling/floor joists (the safest one atleast) is to hire a structural engineer and he will be able to tell you exactly what dead/live load you can have with your floors. Marc

OH.... reading your post again DUH, Should be safe to presume it's not #1 grade (I think) The difference between #2 and #3 also has a lot to do with how many knots are in the wood. Got to run to a gig..................... Marc

Thanx.... I appreciate the input.... I will try your recommendations of contacting pros. Would have to 'assume' (although I know the implications of that) that the floor joists are #2... According to the span tables #2's would be more than enough strength for me adding 2 layers of 5/8" between the joists (with gg b/t the layers) thanx, K

Hi there, I sell lumber for a job, if you take a couple of photo's for me I will tell you what grade it is. Thanks JohnG

JohnGardner wrote:

Hi there, I sell lumber for a job, if you take a couple of photo's for me I will tell you what grade it is. Thanks JohnG

Hi... THANX... I will do just that... What sort of shots should they be? Do I need to show real close-ups of the grain and such? (I can incorporate a ruler into the pictures) K

No just a few feet back showing the general layout of knots. along the length of the boards Knots and there sizes and posistion is what basically determines the visual grade of lumber for strength. JohnG