Residence without footing

[joenorm]

Hi,

Some friends purchased an older home(1940's) with a poured concrete perimeter foundation. They would like to tear the roof off and build a second story. The problem is it has no footing. As far as we can tell the soil is mostly sand and small rocks.

My question is whether an engineer will ever sign off on the second story without a footing? Is it worth the expense of a geotechnical report with the hopes the soils are strong enough to support the home without the footing?

Or is it likely they will have to strengthen the foundation?

thanks

 

[hokie66]

Is not the "poured concrete perimeter foundation" the footing? Some dimensions might help.

 

[joenorm]

There is a stem-wall but no footing under it. It's either 6" or 8" thick.

 

[emmgjld]

Need specific soils information, to include in-place densities & moisture contents & a good description of the soil profile down at least 6 feet below bottom of stemwall, for starters.
I have placed a significant number of 2 story residential structures on 'walls-on-grade, on 'native soils, though most of the situations were responding to low to moderately expansive soils.

 

[joenorm]

So that answers the question of whether I need to get a geotechnical report. Sounds like yes.

 

[LittleInch]

Also does the local authority have any building control requirements?

It's a min of 1m in the UK regardless if what you're sitting on or how long the building has been there if you want to double the weight of the structure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[phamENG]

You should contact a couple of local SEs to find out if they would ever approve something like that. They'll know enough about local soil conditions to have an idea of whether or not it's feasible with or without a geotech report.

 

[LittleInch]

So have you excavated down to the base of the wall?

How deep and was there any sort of footing or literally just 6 or 8" width of wall sitting on the ground? A diagram always helps.

Even the victorians used some sort of spread foundation at least double the thickness of the wall

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MTNClimber]

I’ve seen foundation walls without footings quite a bit. As Emmgld mentioned, it’s common for residential construction in areas where expansive soils are an issue. The wall-on-grade method is used to help obtain a minimum foundation dead load to help resist the expansion potential of the soil. The theory is, the more pressure you can apply to the expansive soil, the less movement you will see.

I’ve also seen it in small commercial buildings in non-expansive areas. The buildings were constructed in the 60’s-70’s. I’m not sure why they did it but the buildings performed fine.

OP, what region of the world is the house?

 

[joenorm]

This is in the Pacific NorthWest, USA. Almost on the beach so very sandy soils.