When i bought my house I didnt have it inspected first (I know.......) and the floors are sagging. At some point the previous owner installed a beam up the middle to resupport the joists. now they are sagging to either side of the beam so I have high spots at the walls and center and low spots between. my floor looks like a big "W". After some detective work i have found that the joists are actually 2x6s that are bowed, notched, doubled, scabbed together, and otherwise compromised in all sorts of stupid ways. i want to replace them altogether. Can anyone tell me what the proper procedure is for this? Due to money reasons I need to do this myself instead of spending big money on a contractor
1st off, is your basement or crawl space dry? This WILL affect the future of your new floor. You want a dry space.
2nd, your existing joists will have nails in them which will "pop" thru the floor sometime in the future if you remove the joist, but not the nails. I don't what access you have to the nails above, is the floor covered? Does it have carpeting and you can pull it back, or is it a vinyl floor covering and its glued down... Additionally the joists will be laid out such that they fall on the breaks of the floor boards, which brings up the next question, do you have T&G 1x floor decking or sheets of plywood? And lastly, what is your span?
So, here's what you want to do in a perfect world, leave the beam. If possible remove 1 floor joist and nails then replace it, one at a time, space them at 16" on center, (14.5" inside gap). For even more support put them at 12" o.c. seeing as they are only 2x6. after about 6 joists go back upstairs and nail them down, lather rinse repeat. You get the drill. maybe it sounds like a lot of work, but you can do it. In fact you may choose to double every other joist to beef up your load capacity. Lastly, look for fir, hem or Doug, both are stronger than spruce.