Contraflexure74
Structural
Hi All,
I have a scenario where I'm not sure what to do.
I have a 2 storey detached domestic house which is situated in an area well known for having poor ground. There are some 1mm cracks in the property but nothing that worries me. The house was built the circa 1970's.
We did some site investigation works to date and to be honest the results are a bit confusing. We have established that the strip footings are 2m down and are 1.1m wide.
The foundations were too far down to expose the bottom of foundation to see what type of soil the strips sits on.
We also carried out some dynamic probing and all 4 probes are consistently bad. At 2m depth we have a n value of 2 (per 100mm) which is extremely pour. This by my calcs gives about 40kN/m2 of bearing capacity at best. The soil is a soft clay. We got refusal from the probes at 4.5m down.
The client wants to convert the attic into a bedroom and add a 2 storey extension to the rear of the property. I'm worried about modifying the existing house with these probe results.
I'm thinking of going down the route of installing a piled raft within the existing house and piling the extension but this will be expensive. Is this overkill?
Should I dig a larger trial hole to visually see what the ground is like at strip footing level??? Or is this a waste of time bearing in mind the poor probe results.
Your thoughts are welcome.
I have a scenario where I'm not sure what to do.
I have a 2 storey detached domestic house which is situated in an area well known for having poor ground. There are some 1mm cracks in the property but nothing that worries me. The house was built the circa 1970's.
We did some site investigation works to date and to be honest the results are a bit confusing. We have established that the strip footings are 2m down and are 1.1m wide.
The foundations were too far down to expose the bottom of foundation to see what type of soil the strips sits on.
We also carried out some dynamic probing and all 4 probes are consistently bad. At 2m depth we have a n value of 2 (per 100mm) which is extremely pour. This by my calcs gives about 40kN/m2 of bearing capacity at best. The soil is a soft clay. We got refusal from the probes at 4.5m down.
The client wants to convert the attic into a bedroom and add a 2 storey extension to the rear of the property. I'm worried about modifying the existing house with these probe results.
I'm thinking of going down the route of installing a piled raft within the existing house and piling the extension but this will be expensive. Is this overkill?
Should I dig a larger trial hole to visually see what the ground is like at strip footing level??? Or is this a waste of time bearing in mind the poor probe results.
Your thoughts are welcome.
