Hello, I have done a bit of research on this topic but still have a few questions and am really hoping to find some advice here. I have an area in my house that I bought in May 2011 that has about a one inch sag. The house is 1967 build, 1300 sqft. cape cod style. There is a crawl space underneath with about a 3 foot height. The sag runs a span of about 7 feet, maybe a bit more, by 7 feet. I don't know if the sag is due to the same problem or a couple along the way. I have attached a crappy diagram of the area just so there is some idea of what I'm talking about. The sag runs from in front of the fridge to behind the water heater and maybe a bit into the bathroom by the tub, with the sag gradually increasing in slope, running towards the hot water heater. The floor has had some water damage and I know I will have to replace it down the line (it's either due to old hot water tank leak or the fact that the tub isn't level so water is running down to the floor on the shower head side). There has been some cracking in doorways, previous owners said they have been there a long time and did not notice them getting worse. I've had a few people look at it including 1 home inspector, one structural engineer and one employee of a foundation repair company. The first two said it would be an easy fix by using floor jack posts, etc. The employee said it was an easy fix.......for $3000.
Being a single woman with two children, and having just bought a home, I do not have $3000 to throw at something that is really just a nuisance right now. I am fairly handy (can do a tune up on my own vehicle, oil change, just for example) and am not worried about doing the work myself, I just want to make sure I'm doing it correctly.
One thing to throw a cog in the wheels is that the furnace is in the crawlspace just to the side of the lowest point of the sag right around the hot water heater.
My plan was to use floor jack posts and install sisters joists on all the joists in the sag area. My problem? I don't know exactly where I should put the floor posts, how many I should use or if I can put a jack under a wall. Any other advice, or even being told I'm way off, is greatly appreciated. Hopefully I was able to paint a clear picture of the issue and am making some sense.