I have started planning to extend the house quite significantly with a deck on footings as the foundation. I recently built a deck of about 50m2. I now want to build 45m2 on it in 1.5 stories. I built it quite robustly. It is 4.5m deep, I have a bearing beam on the outer edge and one in the middle in 195x50mm. On these, there are 195x50 floor joists anchored to the house, with post bases and French (standing plank wall).
I have poured footings. First, I dug out about 0.5m2, poured a full wheelbarrow of concrete into the hole, so I got a base/clump, on top of which I cast the footing with 2 reinforcement bars that were inserted into the bottom clump. The footing holes are about 80cm deep including the base. However, I have quite a lot of space underneath, so I can backfill with excavation materials to achieve a higher frost-free depth if necessary. However, I believe that the house insulates enough, so there should not be any major problems with frost (Gothenburg).
The footings are spaced just under 2m apart. A total of 12 footings on the 45 that will be built over.
The house is a 1940s house with a basement. The ground is primarily compact clay. Does anyone think this could be okay, or do you see major risks with the construction? I want to do this because it provides me with a relatively cost-effective solution. Tearing down the deck, excavating, and casting a slab from scratch is not an option; if necessary, it might be shelved instead.
Grateful for any feedback,
Morgan
