Replies

1. 
   unclemike42 | Mar 09, 2021 03:12pm | #1

   The footing is under the block wall, and what sits between the regular surface hollow block and the less regular (but undisturbed or compacted) earth. Should be poured concrete.

   This footing what you might want to drill into and epoxy some rebar into to help hold the new and old structure at the same elevation relative to each other.

   If you are someplace you need to consider earthquakes or floods, the best plan is to have an engineer weigh in.

2. 
   AndrewSmith_Ontario | Mar 10, 2021 04:15am | #2

   Oh, cool, thanks!

   So I don't need to tie in most of the foundation, just the footing? It seems weird to me that there will end up a long vertical crack where the two foundation walls join. Doesn't that have the same problem as a block wall where the blocks do not overlap from layer to layer?

   Thankfully there are no earthquake or flood worries here.

3. 
   unclemike42 | Mar 10, 2021 06:27am | #3

   Depends on how high the wall is. And what kind of soils you have. (and how water behaves in the soil structure you have)

   And if you will have one side open while the other side is buried. (Is this going to be a crawl space or a full basement?)

   You can drill a small hole in the mortar and use a wire to check the inside depth, then patch the mortar. (or use foam or caulk to fill the hole)

   You can also use a tape measure and some math to get an idea how thick the wall is. measure from a window to the inside and outside edge of a corner of the foundation. (or some other reference, like the edge of a specific block you can locate from inside or outside)

   You can tie the wall together a couple ways. your local codes folks can inform you on the requirements, but you can always go over.

   It is likely yours is hollow block.

4. 
   unclemike42 | Mar 10, 2021 08:04am | #4

   The most solid will mean you have to break into the existing wall and fill one or two cores, and tie to the new wall with rebar and cement mix or grout. (you can put holes into every third course, more or less, use some bent rebar and fill a few courses at a time of the new and old wall together as the new wall goes up)

   Less secure would be drilling holes in the mortar and using rebar or ladder mesh to tie to the new wall.

   It will be as, if not more, important to seal the joint so that water does not enter (and then freeze, which would push things apart).

   Also a good idea to make sure you have perimeter drains, waterproofing and fill that control the flow of water away from the wall, tied in with your existing basement.

5. 
   AndrewSmith_Ontario | Mar 11, 2021 02:27am | #5

   Thanks Mike!