I have a floor beam under our house that is cracked/split at a knot, and has been that way for several years, with no known problems. I thought this might have been caused by an earthquake, but now read that this is common at knots. I am located in No. Cal., and our house is constructed (as many in this area) with 4x6 beams, or joists, on aprox 4' spacing with a 2x6 subfloor; over a crawl space. The last time I looked at the beam, it did not appear to be sagging. I have been reading a great deal on joist repairs lately, and it appears I could sister this beam with 2x6's on each side. I would plan to support the beam with a jack;...a bottle jack is usually recommended, but I've never seen a hyd jack that doesn't bleed down, unless it has a collar lock. Wouldn't a screw type support jack be more stable ? The 4x6 beams are fir, so is fir the wood to use to sister it? I've seen treated wood and maple, oak or mahogany suggested. I've seen some recommend 1/2 " bolts and some just go with screws. I am thinking a combination, with adhesive on the sistering 2x6's. I could take a picture, but not sure how to post it here.