Re: sistering joists

[peg_688]

Why not put in the beam if you can stomach / hide the posts , remember to take those [highlight]" point loads" all the way to a proper footing[/highlight] in the basement / crawl space .  You should be able to go to a good lumber yard and have them size you a LVL / or glue lam beam that could be flush with both the top and bottom of your joist  or at least be able to be fir-ed down flush. Put the old joist in hangers off that flush beam.  She might be wide / wider than normal , the beam   

Sort of complicated supporting the floor / getting the beam in place etc but it can be done . It is simpler to just put the beam under and jack up the joist with the beam but then ya gota beam breaking up the cieling line .

 Either way you'll have to[highlight] slooooowwwly[/highlight] jack the floor back up , If the upstairs floor has been replaced / repaired etc it will be a hard push back up nails , flooring carpet etc will all be fighting to stay where they are .  [highlight]Jack slooowly[/highlight] , make sure your jack bases are [highlight]very very flat and wide [/highlight]or you'll just blow out the floor below .

[highlight] Jacking is very dangerous go slow think way ahead, use good jacks , wiiidddeee bases , and stout posts . [/highlight]

G/L PEG

[highlight]If any thing goes wrong you didn't do it right and I never said anything  [/highlight]    

[glenn-k]

Either that or wood posts should work.  

PEG -- you are such a joker.    I know -- me and my wimpy dial up can't keep up with you.

[glenn-k]

I don't have any span tables here but also we don't know the span- just the width.  PEG or John would probably know what you need -- how far between posts would help them.  

I'm heading to Oregon for a few days so may not be much help - haven't been to my cabin for about a week and a half -- where my books are-- working on the road - then family reunion.

Keep the questions coming - it keeps us out of trouble.

[rshoener]

Oh my bad the distance between the two supports would be 12.5 feet.  I was thinking of using a 4x6 beam, is that enough to carry the load?  Enjoy the family reunion!

[glenn-k]

Sounds a bit light to me but just going off the top of my head -- here is a topic that may help a bit.

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1129253203/11#11

Thanks - I'll enjoy seeing all those "old" cousins -etc-- glad I can't see myself.

[peg_688]

Go to a good lumber yard have them size you a LVL or gluelam beam it will be smaller or as small as it can be , smaller than conventional lumber anyway.

The 4x6 is way to small spanned at 12' , generally 4x6 spans are 4' under house's in crawl spaces and the same when useda window/ door  headers.

The lally  columns would work we useda lot of those back in RI , haven't used one in years out here in PNW . The only down side is IF you need a saddle on your beam which in earthquake country is REQUIRED you'd have to have a welder , like Glenn, weld a beam pocket/ saddle  on the lally column.

A wood post should be sized according to the beam size . You could use a steel" I "beam as well if  glue lam / LVL is to small. You may / should MTL consult a engineer  if your local "GOOD " lumber yard can not size the beam required. Do not go to Home depot / Lowes etc for this service , IMO.

 BTW you will want to get those sistered joist in place before you put the new beam in place , at least lighly tacked beside   the existing joist , you'll play hell "rolling " new joist in beside the old once the beam is in place , remember the joist will be longer than the whole as it needs to bear on both the beam and the beraing wall plate , and when you try to roll the new joist in "corner to corner" the joist will be taller than the joist is high diagonally that is .

 G/L PEG

MTL = More Than Likley

[JRR]

I believe the easiest thing to do would be beef up the bottom edge of the 2x8's.  If you could attach (glue and screw) a 2x4 or a 2x6 on both sides of the joist ...  that would be a lotta "beef".  The add-on's would not have to span the full 16' as the ends of the joists will be in "shear", not bending.  For best results you would want to jack up several of the current joists 'til they are flat and no longer loaded ... then attach the add-on beef to group of joists before removing jacks ... this put the add-on's under stress and they then share the load with the original joists.

This plus bridging between joists should make the floor super stiff.  (But I'm guessing and haven't actually done the math!  Just offering an unproven scheme!).

[jraabe]

A very rough sizing guide for a midline bearing beam under a floor is to use a 6x and then size the depth in inches so that it exceeds the span in feet. That would give you a 6x14 - a bit more than a 4x6  .

This is very rough but is good for [highlight]visualizing the general size[/highlight].

PEG's advice is good - it is likely an engineered beam will be the best choice.