Porch support

Looking to replace the granite posts on our porch with metal columns. (see pictures of porch http://mysite.verizon.net/stamkis/ ) Need to jack up and support the porch in order to remove the granite footings and granite posts. The footings are about 10 or so inches in height and stand on edge. They've shifted over the years and the granite columns are in bad shape too. I would like to keep the granite base and posts as a facade hiding the new metal(filled with concrete or lally) columns.
Since the porch is so unstable I would like to support it in multiple locations before I begin jacking it up. To be honest, I've never used a house jack before and this particular porch setup is challenging.
A few people have given me ideas, but I'm not confident in using any of them. Everyone seems to be in agreement that the front corner of the porch needs to be handled first.
I'll go through some of the ideas below. 1. Place a big turn-style house jack two feet or so behind the corner granite post. Place a 4x4 pressure treated post vertically above the jack. (I assume that is how they work.) Run a 4x6 beam diagonally across two adjacent band joists. Jack up very slowly as necessary supporting both bands with the one cross beam using a vertical 4x4. Then dig a hole for sauna tube directly behind the corner granite posts. Fill with concrete. Let it harden. And, basically do the same thing for the permanent structure. Run a short support beam diagonally across the two band joist and put a lally column beneath it... resting on the new concrete.
Personally, I would want to move the granite out and put the steel post directly in the corner where the original granite post were. Almost seems there should be two metal post there. I prefer not to use pressure treated wood because in 15 years or better they will have to be replaced.
I don't know anything about construction practices but the first cross beam idea seems a bit scary and running a cross beam to support the porch doesn't appeal to me. I'm also a bit worried about digging and jacking without the rest of the porch being better supported.
2. Idea # 2 Similar to the first except using a longer and stronger 8x8 beam to run across the diagonal. The beam would be supported on the two outer sides of the porch using a platform at one end and a jack on the other. Couldn't quite get the concept of what this person meant by platform. Something solid for sure.
He also suggested similar scenarios for supporting the rest of the porch at the same time. Again, I was a bit puzzled about how this would work. What I like about his idea is that there would be a lot of room to work. And, no digging would take place near jacks.
3. Idea #3 Get a 2x12 rest it flat side under the bank. Angle it so the bottom rest on some solid wood. Drive two 2x4's a couple feet into the ground behind the wood to keep the 2x12 from slipping. Also, nail two pieces of wood along the top side of the 2x12 at the bank joist to keep it from slipping side to side.
Previous to this, the corner could be jacked up using the existing granite base. Then, let it rest on the 2x12. Once the porch is supported then move the granite base and columns and dig the sauna tubes. Then place posts. My main concern is how do you keep the 2x12 board from slipping forward at the band?
I like this idea. I'm just not over-confident in it. Don't worry, I will have someone more knowledgeable help me doing this.
My main problem in jacking this porch up are as follows. I want to move the granite base and still support the porch at the same time. If it were simply a matter of jacking the house up vertically on the base, that would be a piece of cake. However, I would like to move the base and dig in the same area to put in the sauna tubes. Thus, I most likely need to be away from the area when jacking it up. Any ideas on how to jack up this porch are appreciated. A web site with diagrams might be even more helpful.
As you can probably tell I am not getting the best advice. One contractor recommended I put up some 4x4's under a number of the joists. Then, run 2x8's perpendicular to the existing joists, supported by 4x4 posts. I put in a few 4x4's and everyone started telling me all I was doing was holding up part of the floor, not the porch. They said the same would happen when I ran the 2x8's under the floor joists. So, I abandoned that plan because the bands were not directly supported.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.