Rethinking the foundations! - My House Extension

A one storey extension
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Rethinking the foundations!
Tuesday, 10th April: Well, what a day this turned out out to be!

Building Control visit Stage 1 - Commencement: I started by calling the the building control department as I had not heard from them i wanted to have my first on-site discussion meeting. I called at 10:00 and he was here at 11:30 - terrific service!

I then went on to order 2 tonnes of builder's sand and twelve bags of concrete. These will be delivered Thursday morning.

We had a good discussion and some of things he said about what I would need to do for the floor slab really surprised me - more on that later I'm absolutely sure!

Anyway, in regard to the foundation trenches, he said that I need to dig a bit deeper down to 600mm. This was required to ensure that the foundations do not get frosted. OK, more digging. However, he was really helpful.

This meant that my drainage pipes and the gas pipe would well above the strip foundation so I could pour 6" of concrete straight into the the trench with worrying about building channels for the pipes. However, in regard to the gas pipe he said I should talk to gas people as this was not within his bailiwick.

I was thinking by this time that it might be better to just get the gas people and move the pipe, this would simplify things so much from a foundation perspective.

I called Southern Gas at 11:30 (in Scotland) and was told I needed to talk to the 'Plant Protection' department and I was given a number to call. I called talked to a real person - not in Mumbai! - who said she would call the local gas engineer and get him to undertake a site visit.

Well what a shock! At 13:30 a gas van arrived outside and out popped Sydney, the local engineer. He said it would be quite easy and quick to do as I already dug out the trenches. All they would need was another 18" at either end to accommodate a bend in the pipe. All they needed to do was to clamp the nylon pipe shut cut it, add in a short length and it would be done. The only problem there was a queue and it would take a about a month to do it. He was very helpful and said he would call back in the morning with the name of the man to call, who will provide the correct form for me to fill out.

This delay will not affect build times as I can lay the foundations under the pipe and I can't start building the wall as I am unable to get the facing bricks until the end of April.

It's possible to see building regulations on-line on the government planning portal and below is a drawing about placing steps in foundations. Now... I have no idea whether these rules, dated 2004 are up to date but I would have expected them to be!
The building control guy said I should remove the disused drain pipe I found in the trench and just checked in the inspection camber to ensure that it was actually unused! Judging by the cobwebs in the inspection chamber, it wasn't so out came the lump hammer and the drain was gone.
I spent the rest of the afternoon digging out the lower trenches to the required 600mm. Fortunately this was not too onerous as the soil was fresh and did not include too many brick bats!

I need to dig out the top half, get the inspector back to improve the trenches on Thursday and then maybe I can start pouring concrete on Thursday?
I need to dig out the top half, get the inspector back to improve the trenches on Thursday and then maybe I can start pouring concrete on Thursday?

I completed the Alteration of Service form this morning and sent it off to Southern Gas. I explained the was no digging to do and that Until they did this job my build is held up!
Wednesday, 11th April: Digging the last bit of trench I came across another disused length of drain pipe. A lump hammer soon removed the discovery! I assume before the kitchen was built in 1932 there was an old outside toilet on this corner of the building.
I've hung the gas pipe from pieces of wood to keep it clear when I pour the foundations - hopefully starting tomorrow.
This is the temporary layout of the kitchen drain until I drill a new hole in the kitchen wall.
This is spoil pile #1!
This is spoil pile #2!
This is spoil pile #3!
This is spoil pile #4!

I am absolutely amazed at the amount of soil and bricks I have had to dig up and move for such a small extension.
The last activity of the day was to pick up three reinforcement rods for the foundations - where there is a step in the level they need to be reinforced according to the building control inspector.
Thursday, 12th April: Building Control visit stage 2 - Foundation excavations: The building control surveyor came around to look at my trenches after he told me the other day to go down to 800mm. His opinion was that in the lowest trench I still needed to go down a further 200mm to reach a solid enough subsoil.

So... I better start digging and arrange for him to come visit again first thing in the morning. No cementing today!
OK, I've now dug down to 800mm and have hit the solid sand subsoil at long last!

Interestingly, I also found another 1" water pipe at that level that I can only assume is now disused.

I hope the building control surveyor will now give me the go ahead tomorrow morning.
Copyright: Chris Gare 2007 - 2018
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