Garden room on 'made up' ground

[occy]

I am building a garden room (7mx4m) at the end of my garden. The room will be of timber construction and sat on 34 screwed rods (m24) concreted into the ground.

Digging my holes using post hole shovels I have discovered that the ground I'm digging into has been made up of all sorts of junk. I have found bricks, tiles, metal, asphalt and various other building materials below the top soil. I have dug these holes to a depth of 700mm and definitely not hit virgin ground at the bottom of the holes.

I have come up with a possible solution and would like some expert opinion as to whether it would work; I was thinking of using a petrol post knocker to knock a 5ft scaffolding tube through each hole, hopefully creating a friction pile or possibly hitting better ground further down. I would leave say 200mm stuck up at the bottom of the hole for the concrete to adhere to.

I am open to any alternative solutions to this problem, especially if anyone has had first hand experience.

I have uploaded a couple of pics of the holes.

Thanks in advance....................

[Iceverge]

If you're using a company to provide helical screw piles or ground screws they would have a solution.  

 

As I understand it they just keep going down until an appropriate torque is reached with each pile which corresponds to a bearing strength.  The screw may need to be lengthened with galvanized tubing which is cut off at the correct level once piling is complete. 

 

 

[occy]

Hi Iceverge, I'm using a different method. I'm not using helical screw piles, I'm concreting galvanized M24 threaded bar into the holes i've dug. The base timbers then sit on a 'shoe' which is a piece of steel channel held up and adjusted to level by the nut underneath. (similar to pic)

[Mr Punter]

4 hours ago, occy said:

I am building a garden room (7mx4m) at the end of my garden. The room will be of timber construction and sat on 34 screwed rods (m24) concreted into the ground.

Digging my holes using post hole shovels I have discovered that the ground I'm digging into has been made up of all sorts of junk. I have found bricks, tiles, metal, asphalt and various other building materials below the top soil. I have dug these holes to a depth of 700mm and definitely not hit virgin ground at the bottom of the holes.

I have come up with a possible solution and would like some expert opinion as to whether it would work; I was thinking of using a petrol post knocker to knock a 5ft scaffolding tube through each hole, hopefully creating a friction pile or possibly hitting better ground further down. I would leave say 200mm stuck up at the bottom of the hole for the concrete to adhere to.

I am open to any alternative solutions to this problem, especially if anyone has had first hand experience.

I have uploaded a couple of pics of the holes.

Thanks in advance....................

 

From the photos there may be some asbestos in there, so be cautious and assume it is.  Keep it damp and not create dust.  A decent mask is a must as well.

[Iceverge]

6 hours ago, occy said:

Hi Iceverge, I'm using a different method. I'm not using helical screw piles, I'm concreting galvanized M24 threaded bar into the holes i've dug. The base timbers then sit on a 'shoe' which is a piece of steel channel held up and adjusted to level by the nut underneath. (similar to pic)

 

 

Ah, I'm with you now. I'm pretty sure what you suggest would work perfectly well. 

 

Lots of buildings are built on friction piles, concrete and steel in large construction. Lots of timber piles in the New World and historically in Europe. 

 

I'm not a structural engineer but you might want to consider your soil type for movement associated with soil moisture content.  Someone else will know better. 

 

Also have you considered using stainless steel in lieu of glavanised M24. Some galvanising can be hit and miss. 

 

 

 

[occy]

4 hours ago, Mr Punter said:

 

From the photos there may be some asbestos in there, so be cautious and assume it is.  Keep it damp and not create dust.  A decent mask is a must as well.

Cheers for that. Good call.

[occy]

1 hour ago, Iceverge said:

 

 

Ah, I'm with you now. I'm pretty sure what you suggest would work perfectly well. 

 

Lots of buildings are built on friction piles, concrete and steel in large construction. Lots of timber piles in the New World and historically in Europe. 

 

I'm not a structural engineer but you might want to consider your soil type for movement associated with soil moisture content.  Someone else will know better. 

 

Also have you considered using stainless steel in lieu of glavanised M24. Some galvanising can be hit and miss. 

 

 

 

 

Cheers Iceverge. I had considered stainless screwed rod but couldn't justify the extra cost. Galvanised should be fine as they are all under the cover of the building so should be kept relatively dry.