Can I rip my joists?

[gls]

I'm doing a remodel on a ground floor room in a two story house. The room has a very low ceiling, and I'd like to raise it. The floor joists are 2x10 doug fir, good quality, very tight grain (built in early 60's; not the junk that passes for wood today) and few knots. According to the AWC Span Calculator, 2x8's would be adequate (or close) for the distance I have to span, depending on the grade of the wood. There are no load paths through the floor, just living space above. I'd like to rip these joists down to 2x8 in order to get a little more headroom. (And yeah, in this case a little bit is a big deal.) I figure I would add some material to compensate for the material lost. If I wanted to go nuts I could rip some LVLs to 2x8 and sister them in, although I think that would be overkill. I could cheap out and laminate the joists with glued plywood. Or I could do something in between. So, my question is, am I crazy? How would you approach it?

[pushkins]

You never mentioned the actual span of your existing joists, but your comment "or close" seems a little scary, span charts list the maximum span, oversizing for a span is obviously okay but stretching a span by even as little as inches is a big worry.

[gls]

You never mentioned the actual span of your existing joists, but your comment "or close" seems a little scary, span charts list the maximum span, oversizing for a span is obviously okay but stretching a span by even as little as inches is a big worry.

Thanks for the quick reply! The span is 12'6, and the span calculator gives values that are either longer or shorter than that depending on the grade of the wood. Using the default Live load of 40 psf and dead load of 10 psf, I get the following spans:

• Select Structural = 13' 7"
• Number 1 = 13' 1"
• Number 2 = 12' 9"
• Stud = 9' 9"

I'd estimate these boards as between No. 1 and No. 2, if anything closer to No. 1. It's also pretty lightly loaded, just two bedrooms with no load paths. That's not even considering that I could sister something in, or laminate the joists to get more strength. (Looks like I'm managing to convince myself here...) Let me rephrase my question a bit: How can I get enough strength to span 12'6 with as little height as possible? (Something cheaper than titanium box beams, preferably...) Thanks a million for your advice!

[pushkins]

According to AWG (American Wood Council American Wood Council)

Using your spans and loads and on 16" ctrs.
SPF #2 2x8's will only span 11'6"
SPF SS 2x8 will span 12'7"

On 24" ctrs.
SPF # 2 will span 10'3"
SPF SS will span 11' 0"

It will depend greatly on your local building department and how they interpret the code but technically your not allowed to cut a floor joist in the middle 1/3 so technically ripping off 2" would not be allowed. I doubt if you asked they would let you just rip 2" off, however if you were to do that one by one and add a 2x8 SPF#2 sistered hard against the existing floor joist, glued and nailed or bolted as you go you probably would be allowed.

Another option would be to bolt a 1/4" or 3/8" steel plate to the existing joist after you rip it down the bolts would likely need to be 1/2" drilled on 12" ctrs. staggered. The plates would likely run around $30 each, so it might end up costly if your doing a great deal of joists.
However if you consult an engineer (might cost about $200) who will come out and make calcs. for your specific job you may be able to cut those joists down to 6" and plate with 1/2" steel. The best part with that is that the engineer will stamp the drawings and your good to go no matter what the building inspector says.
So if your after inches this option would give you double your starting amount.
If it were my house and I couldn't go down through the floor to get room height I'd consult an engineer to see about getting down to 6" joists with steel plates or the cheaper option of ripping down the existing joists to 2x8" and adding on 2x8"'s.
What is the height your going to have ?
A habitable space (according to code 305.1) must have a ceiling height of 7' min.

[gls]

Thanks for the great info. If I could go to a 6 inch joist with steel plates, that would give me a finished ceiling height of 7'7", which would be a whole world better than the claustrophobic 7'4" setup I have now. You think it would take a half inch thickness of steel? That's a healthy piece of metal... Any chance I'd be able to find one that was predrilled, or will I need to drill them? I have a drill press and tooling, but 120 holes will take a while. I've got 10 joists. I guess I should scare up an engineer and a steel yard. Thanks again.

[pushkins]

Most steel yards will pre drill the plates for you. The yard I get mine from even supplies the bolts with the plates. Steel prices can fluctuate from yard to yard last time I bought a 12' 11" x 1/2" x 8" piece (three weeks ago) drilled with bolts, nuts etc... it cost $78 but I also paid for delivery.
Another option might also be "C" (or maybe "Z") purlins these could actually work out cheaper added to existing joists cut down.

[russell]

Hello Pushkin........Thank you for this information maybe you can help me here too.

The problem with my joist are that they are sagging. They are 2X8 and cover a span of 12' 3". I know that they could be sistered easily enough but they have 3 inch ducts running through them as in SpacePak air conditioning.
So two questions:
1. Could the sister joists be cut where the ducts run through....pushed up into place and then properly secured?

2. Or could C Purlins be used and what would their dimensions be?

What do you think is the better option here based on economy and efficiency?

[HayZee518]

who is the joker that cut three inch holes in the joist? building inspector should have shot him and told him to replace those joists!

[pushkins]

The problem with my joist are that they are sagging. They are 2X8 and cover a span of 12' 3". I know that they could be sistered easily enough but they have 3 inch ducts running through them as in SpacePak air conditioning.
So two questions:
1. Could the sister joists be cut where the ducts run through....pushed up into place and then properly secured?

No, unless you use full length and full sized (2x8) material anything you add will do little to stiffen the joists. Even plating either side with 1/2" ply would not work as again you'd be cutting out a 3" section to fit either side of those ducts you mentioned.
C purlins would not be effective either as again they would need to span the entire length.

Where are these floor joists situated in the home, with a crawlspace below, a basement below ?

[russell]

Actually the joker cut 4 3 inch holes in the joists 14 inches apart. Hard to find until you remove the drywall material from the ceiling. Yet I think that the joists had long since developed the sag before the AC was installed. The openings start just after the joist leaves a supporting wall or it could have been worse!

[russell]

No unless you use full length and full sized (2x8) material anything you add will do little if anything to stiffen the joists.
C purlins would not be effective either as again they would need to span the entire length.

Where are these floor joists, with a crawlspace below, a basement below ?

Actually these joists support the 2nd floor above a first floor kitchen and they dip down in the middle about 5/8 of an inch in the center. And I would use full length sister joists but they would have to be cut to allow the AC tubes to go through. Actually I could pull these ducts back through the existing joists and using a large hole saw drill through the new sisters to allow the ducts to remain in place. Overall this would certainly improve the strength of the existing joist, would you agree?