Building over an old septic tank? (Non EU project)

mrcheez

I'm planning a one storey bungalow on a project outside the EU. I mention this as the regulations are different than in Ireland.

One thing concerning me is that one corner of the site currently has a septic tank which is currently in use. The plan is to build a new one and then empty/fill this septic tank with soil or sand and tamper the ground thoroughly before laying foundations.

Will that be ok? Or still risk of settlement over time?

Calahonda52

Are u building over the existing tank once its decommissioned?

differential settlement will be a risk, depending on what type of foundations you are building.

If not digging it out, then a lean dry mix of concrete would be a minimum: you could go out as far as 18:1

mrcheez

Plan is to build over it, and actually a corner of the house will be over the old septic tank (which is what worries me).

Builder suggested something about installing the supporting columns a bit further away rather than directly into the septic tank.

muffler

The tank should be removed completely in my opinion and a structural engineer engaged to design and oversee/certify an appropriate foundation. Don't let your builder do the designing.

T-Maxx

It depends to a large extent on the details ie the house location wrt the tank, tank size, foundation, soil, etc. It could very well be ok to just fill it in. On the other hand it may not. Err on the safe side, don't be sorry later.

mrcheez

Aye, it's a bit risky I'm going to hold off, cheers