Hello; First thing from your pictures. It looks as some sort of "wedges" were cut and driven in to take up the space on one of the support columns. They may be fine as they are but I would check them out. That they are at differing angles caught my eye. Also the angle they are cut at makes me suspect they may not be driven very deep into the space. ( It seems to me that the pitch could have more shallow.)
You may already know this but wood that touches dirt should be the treated type to discourage termites. Also wood on dirt will likely draw moisture. I would likely pour a cement footer or use the preformed cement bases.
Also try to determine if the soil is compacted where the supports will be placed and not some sort of fill. If you think it may be fill, then some sort of adjustable support may be better to use. A screw jack perhaps.
One thing you may also consider is to "block" between the joists. A block of dimensional lumber cut to fit betweeen the floor joists. This ties the joists together structurally and is supposed to help transfer the load. You can still (and likely should) add support columns under the joists.
Sistering will make the flooor structure stronger and also should be in addition to the support columns. The issue with sistering often is having the space and clearance to manuver the long bit of lumber about and get into place. Also are there any plumbing or electrical runs to deal with. If you can sister consider the use of both construction adhesive and screws to adhear the new joist to the old.
The photos others posted show some of the various ways to approach the job. There is no one right way. Working in a crawl space can be tough. I counted the blocks in one of your pictures. If they are eight inch blocks you have over 40 inches. That is a decent crawl space with more room than many. Still going to be a chore.
Good luck.
You may already know this but wood that touches dirt should be the treated type to discourage termites. Also wood on dirt will likely draw moisture. I would likely pour a cement footer or use the preformed cement bases.
Also try to determine if the soil is compacted where the supports will be placed and not some sort of fill. If you think it may be fill, then some sort of adjustable support may be better to use. A screw jack perhaps.
One thing you may also consider is to "block" between the joists. A block of dimensional lumber cut to fit betweeen the floor joists. This ties the joists together structurally and is supposed to help transfer the load. You can still (and likely should) add support columns under the joists.
Sistering will make the flooor structure stronger and also should be in addition to the support columns. The issue with sistering often is having the space and clearance to manuver the long bit of lumber about and get into place. Also are there any plumbing or electrical runs to deal with. If you can sister consider the use of both construction adhesive and screws to adhear the new joist to the old.
The photos others posted show some of the various ways to approach the job. There is no one right way. Working in a crawl space can be tough. I counted the blocks in one of your pictures. If they are eight inch blocks you have over 40 inches. That is a decent crawl space with more room than many. Still going to be a chore.
Good luck.
