Quick and nasty questions...

[stef99]

Hi, I'm about to embark on building my own extension. I have a friend of the family who will be building the shell, but not 100% promised to help me with the foundations.

Due to the area at the back of my house, I expect I will have to dig the foundations by hand... this is not a problem as I have the time to do it (hopefully)

So my question is the size I should be digging.
I am in touch with building control and have my plans drawn up, but getting hol o building control is not always easy so I decided to ask here.

My extension is a two story, so I need to dig (I think) 1.2m down and 600mm wide.
and then fill it with footing concrete.

This is fine, but do I need to have a layer of dolomite or something at the bottom of my footings, an will I need to have a metal mesh in there also?

After my concrete has been poured, I can simply tell my builder all is well, and he just needs to start the brick work?

I may also need to move a drain. can I just bury a new drain in position where I need it? and refill it with soil?

 

[^woody^]

..... and have my plans drawn up

Are they drawn with invisible ink?

 

[paralandey]

Hi Stef

I have just completed my 2 storey extension, having done the groundworks myself. It is vital that you get on the right side of building control inspector or they can make your life hell. They will want to inspect your footings prior to the concrete pour. You generally need to go down 1m and 450mm wide. The inspector will want to see you have gone down to just below the existing foundations in depth - I needed to get down to 1.2 m to do this on my build. You do not need to put anything in the bottom of the footings but make sure you get them level otherwise it makes it difficult for the builder. I recommend you hiring a laser level to do this

As for the drain you will need to get authorise of building control, they may say you need to dig a new soak away

Good luck

 

[tony1851]

Many inspectors consider 18" a bit narrow for foundations for 2-storey extensions;
24"is a safer bet.

 

[paralandey]

Tony you are quite right, sorry was thinking about that as I typed yes 600 mm is what I did too

Sorry Steph

 

[noseall]

My extension is a two story, so I need to dig (I think) 1.2m down and 600mm wide.
and then fill it with footing concrete?

1m deep 600mm wide.

This is fine, but do I need to have a layer of dolomite or something at the bottom of my footings, an will I need to have a metal mesh in there also?

No, just a clean trench bottom.

After my concrete has been poured, I can simply tell my builder all is well, and he just needs to start the brick work?

Yes. Make sure the top of the concrete is level and coursed down from dpc.

I may also need to move a drain. can I just bury a new drain in position where I need it? and refill it with soil?

No. The drain will need protecting so that the settlement of the foundation concrete has no influence on the drain falls.

 

[stuart45]

You might have to go deeper stef99 if the ground conditions require this. You should be able to contact BC first thing, or later on in the afternoon.
Here's an example of one in shrinkable clay near trees.

Untitled

• stuart45
• 30 Jun 2013
• 1

 

[stef99]

Hi, just wanted to say thanks for the comments made,

I have only one more question... If the footings are poured by the concrete supplier, won't they make sure the levels are ok?

Im under the impression, that I simply dig out the trench to my required sized, and the concrete is simply poured straight in.
Do I need an kind of temporary wooden walls made up (kind of like a wooden mould or something?)

Fortunately I don't have any trees near to my build so I ok with that.

The drain is another story though, im not sure what you mean by

The drain will need protecting so that the settlement of the foundation concrete has no influence on the drain falls

do you mean that the drain will need to be mechanically protected so that the concrete pouring does not "knock it out of place"?


[/b]

 

[stuart45]

Hi, just wanted to say thanks for the comments made,

I have only one more question... If the footings are poured by the concrete supplier, won't they make sure the levels are ok?[/b]

Not much chance of that. Set your levels first.

 

[stuart45]

Hi, just wanted to say thanks for the comments made,

Im under the impression, that I simply dig out the trench to my required sized, and the concrete is simply poured straight in.
Do I need an kind of temporary wooden walls made up (kind of like a wooden mould or something?)
[/b]

Should be able to pour without formwork.

 

[noseall]

do you mean that the drain will need to be mechanically protected so that the concrete pouring does not "knock it out of place"?

Depends where the drain is located in relation to its height position in the foundations.

But yes, basically the drain pipe needs to be protected from any push from foundation settlement etc.

It can either be shuttered each side and lintelled over, wrapped in compressible material or lintelled through the masonry, depending upon its position.

 

[stef99]

Hi, just wanted to say thanks for the comments made,

I have only one more question... If the footings are poured by the concrete supplier, won't they make sure the levels are ok?[/b]

Not much chance of that. Set your levels first.

Hmm, so to redefine, dig it out and mark my levels with bits of string, so when they come to pour it, I know its level?

or instead of using string, maybe use a simple wooden frame along the inside of the trench, kind of like a marker?

I expect my builder will be able to help me with this, so I'm only asking out of curiosity. Also, I think I have all the ansers to my question, and would like to thank you for the advice

 

[stuart45]

Have a look at the photo. The metal pegs in the side of the trench are the level.