jack post

Mark

making even slow or gradual changes in the floor level of a house will probably crack plaster or drywall. so be prepared for a lot of repairs.

I did a little of this last year and I suggest getting it "close enough" and either "letting it go at that" or levelling the floors from the top with grinding and building up low areas before installing floor coverings. an old house will never be perfectly square, plumb or level. Most people call it "character"

A 3 inch steel pipe is vastly stronger than a 4x4, when both are used as an unrestrained column. This is because the strength of an 8 foot long column is critically determined by buckling, not gross cross sectional area or compressive strength of the material. The buckling stress is a function of the stiffness of the material and the geometry of the section. In this, steel is much superior to wood, and a hollow pipe is much superior to a square. You can increase bearing strength still further by filling the pipe up with concrete, as with Lally columns.

It will do you no good to start jacking if the supports under the posts are inadequate. You also need to understand the loads placed on the various columns, and why the floors are uneven -- were the joists inadequate, have the sills rotted, is the foundation failing, etc.

Steel, copper, and other metals have doubled in price in the last couple of years because the Chinese making all those inexpensive goods sold at Walmart now want washing machines, cars, and other amentities. Wood has gone up as well, perhaps due to cheap mortgages in this country, but not as much. A 6x6 might be a reasonable alternative to a steel column for typical loads, but it would need a more thorough analysis.

Steel can be designed with a smaller safety factor than wood, because the material properties are better controlled during manufacture and the steel is more predictable. Wood does benefit from load duration factors not applicable to steel, but these do not apply to a simple bearing column.

The theory of engineering design of wood has advanced considerably since 1935. At the same time, wood quality and the allowable design values have gone down significantly. The genetically engineered monoculture plantations found in our "renewable resource" forests may grow a lot of wood really quickly, but at 3 growth rings per inch the lumber is nothing like the old growth typical of 1935. A 6x6 today uses practically the entire tree, and the likelyhood of a concealed knot or other defect weakening the post is fairly high, compared to quarter-sawn timbers of yore.