Foundation Stabilization and Repair/Collar a support pillar; rebar or no rebar?
The house is a two story Victorian. One of the newer (25 years old?) cinder block pillars was poorly placed and appears to have sunk approx 8- 10 inches. I have had two construction people (not engineers) look at it. They tell me that it (the sinking) happened a long time ago and that the pillar is "done sinking" It appears that the concrete flooring was compromised when drain tile was laid beneath the floor. My question is, I want to put a collar at the base of the cinder block pillar, which is about 8 cinder blocks high. One of the construction guys said I should use rebar, drill through the bottom cinder block, pass the rebar through. This will give even more support and help prevent sinking. The other construction person said, NOT to use rebar, because it may compromise the strength of the cinder block pillar. I would really appreciate your opinion. Thank you.
By your description it sounds as if the block pillar may be in the basement and resting on top of a concrete slab. However, being only 8 blocks high, is it perhaps in a crawl space?
At any rate, the pillar should be supported by a footing whether beneath the slab or on a crawl space floor. If no footing exists then adding a "collar" may not solve the issue long term. You are in fact, adding more weight to the slab and supporting structure. Any "collar" would be better suited to wrapping the existing footing to increase the bearing area on the soil supporting the load. This would require removal of the slab around the column to expose the footing, assuming one exists. You would want to dowel into the footing to bond the new footing extension.
It is very difficult to say that settlement will not continue at some reduced rate over time.
You could consider the installation of a deep foundation to insure against future settlement.
A helical pier, or similar could be installed and attached top the existing footing or slab, depending on the situation.
My apologies for the slow response a I was on a project out of the country.
Good luck with your repair.