I am a first home owner based in Sydney. I have water pooling in my crawlspace so I was advised by a structural professional to lay a french drain around the perimetre of my home. I watched hours of french drain videos from Apple Drains on YouTube and thought a foundation drain would be a good idea.
So I dug a trench immediately next to the foundation wall so that I can expose the wall that was below grade / buried where I can apply some waterproof liquid rubber.
When I dug though, I was expecting the brick wall to go down deep (maybe 2 feet) which would be sitting on a concrete footing protruding away from the house. Basically all videos I have watched made me expect the wall to be buried quite deep.
However, I only discovered three layers of bricks below grade and thought surely this isn't it? This isn't the foundation footing that I see on videos? Its just 3 layers of brick cobbled together in a messy fashion. I dug deeper to see if there was more wall underneath and discovered there isn't any so it turns out it is the foundation footing.
The problem - and my mistake
While digging though through the clay, bits of clay right underneath the footing were removed along with the clay next to it. I didn't think this was a big problem at the time nor that I thought I was undermining the foundation footing.
The red circle is the undermined bit. So far, I have backfilled the space immediately below the footing (lowest course of brick) with the clay that I dug out and compacted it as much as I can with my hands (basically punching the clay into the space so that it can be molded in).
This isn't complete, of course, as the area that supports the footing is 45 degrees down and away from the house.
So I guess my question is:
- how badly have I messed up; and
- what do I do now to rectify the situation?
I have been planning to backfill the trench with "Crusher Dust" and trying my best to compact it as well as I can about 2-3 inches to form the base of the french drain. Then adding in the non-woven geofabric, then backfilling about 2 inches with 20mm gravel for drainage to form the base of the french drain pipe and then backfilling the rest with the same 20mm gravel.