Framing and Sub-Flooring - need joist advice
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alligatorob
07-16-09, 05:27 PM
I am restoring a historic house in Georgia, the second floor is currently supported by 2x6 joists on 24" centers with a 16' span. If at all possible I would like to reinforce these by sistering in more 2x6 joists. To do anything else would require changes to the historical nature of the place. Does anyone know where I can find span tables or direction on calculating spans of sistered 2x6? I would be willing to sister as many as I need, even 4 or more per joist. Problem is I don't know if this can be done or how to figure out how many I need. Any advice will be appreciated.
chandler
07-16-09, 08:31 PM
Welcome to the forums! Here ya go Maximum Span Calculator for Joists & Rafters (http://www.awc.org/calculators/span/calc/timbercalcstyle.asp). See if that helps.
Confirmed GatorHater......Go Dawgs.
Confirmed GatorHater......Go Dawgs.
GBR in WA
07-17-09, 01:10 PM
Sorry that table from Chandler did not help. You have a problem. They should be spanning 8'6", not 16'. When you sister, you increase the carrying capacity by 2. The span doesn't change unless you go to an engineered system, or steel beam. You need to shorten the span. Wood is rated for the span to safely carry the given load. I would consult a Structural Engineer. Be safe, G
ecman51`
07-17-09, 04:19 PM
I have had to deal with houses of historic vintage. What can happen say if a house is built in the 1800's is that one can start renovating and think that something was built a certain way, when in reality, it may have been remodeled in 1920 and again in 1960, etc. So that when you come across something like this extraordinarily long clear span, maybe at one time eons ago, someone removed a supporting wall below.
Not saying that is your case, but sometimes that's the case. The way it is now, is there a big swag in the middle of that room? What is doubley worse about your floor is not only is the span 16 feet, but the spacing is 24 inches. :eek: I suspect though that these 2 x 6's are the rough sawn, closer to full thick and width variety, which would make them stronger than today's 2 x 6's. But it is still way unacceptable, if what you say is correct.
That is why I wonder if the place was remodeled years ago and some wall below was removed. They knew how to build things right, years ago. Carpenters back then were real carpenters. So this raises the red flags.
Not saying that is your case, but sometimes that's the case. The way it is now, is there a big swag in the middle of that room? What is doubley worse about your floor is not only is the span 16 feet, but the spacing is 24 inches. :eek: I suspect though that these 2 x 6's are the rough sawn, closer to full thick and width variety, which would make them stronger than today's 2 x 6's. But it is still way unacceptable, if what you say is correct.
That is why I wonder if the place was remodeled years ago and some wall below was removed. They knew how to build things right, years ago. Carpenters back then were real carpenters. So this raises the red flags.
chandler
07-17-09, 08:21 PM
I agree with G, in that sistering with dimension lumber won't help in your situation. However, engineered lumber sistered to the existing lumber, and resting on proper support on the ends would help immensely. The chart was to give you the maximum span of lumber only, and you were way out of the parameters with your lumber, especially on 24 oc.
Bud9051
07-17-09, 09:33 PM
Just a point to mention, if you get some engineered lumber to sister to those existing floor joists, you are most likely going to have to lift that ceiling a bunch. And since engineered lumber doesn't give a whole lot, will you be able to move it enough? And are there walls upstairs that will be damaged?
Not sure if there are tricks like contouring 10" sisters to fit that would be allowed?
My 2 cents
Bud
Not sure if there are tricks like contouring 10" sisters to fit that would be allowed?
My 2 cents
Bud
alligatorob
07-18-09, 06:31 AM
Yes the old joists are rough sawn and actually more like 21/2 x 61/2 and they are very hard heart pine. So they are a lot stronger than modern lumber, I guess that is why the have held up so long. The real spacing varies some of the joists are as far as 26" apart and some as close as 18", 24" is just kind of a nominal average.
The house was built in 1853 and there has been no remodeling, never was any support below this floor and no walls sit on it above. This is a 16' x 18' room, same size up and down stairs, no Originally it had full 11/4 inch 12" wide t&g heart pine floor and ceiling and the boards were a full 18' long, I imagine that must have also added strength. The ceiling is still there and in good shape, but someone removed the flooring exposing the joists, I would guess the flooring was removed for resale before I got it. Surprisingly the floor does not sag a whole lot, but when you walk on the joists they are pretty bouncy. Not sure what it was like before the floor was removed.
So I would really like to figure out a way to do this within that 6" thick existing floor space, that would save the old historic ceiling below and let me put heart pine back in for flooring. Sounds like you guys think the only way to go is some kind of engineered joists, any idea who makes such a thing in 6" or where to get it?
Thanks again.
The house was built in 1853 and there has been no remodeling, never was any support below this floor and no walls sit on it above. This is a 16' x 18' room, same size up and down stairs, no Originally it had full 11/4 inch 12" wide t&g heart pine floor and ceiling and the boards were a full 18' long, I imagine that must have also added strength. The ceiling is still there and in good shape, but someone removed the flooring exposing the joists, I would guess the flooring was removed for resale before I got it. Surprisingly the floor does not sag a whole lot, but when you walk on the joists they are pretty bouncy. Not sure what it was like before the floor was removed.
So I would really like to figure out a way to do this within that 6" thick existing floor space, that would save the old historic ceiling below and let me put heart pine back in for flooring. Sounds like you guys think the only way to go is some kind of engineered joists, any idea who makes such a thing in 6" or where to get it?
Thanks again.