Building a Domestic Extension in Stages

[limerockconstruction]

Although 150mm is the minimum in the book, in practice 225mm has always been regarded as the min.

So for going by the book I get called 'amateurish'.

Who said amateurish? Although it's true....

 

[andrew54]

So for going by the book I get called 'amateurish'.

You would be considered clinically insane to rely upon 150mm of concrete for a two storey extension, even way back when.

Foundations are fundamental and are extremely difficult to rectify. Adding an extra few inches in depth would not cost much.

Do you always do things to the absolute minimum?
Did i say amateurish?

I meant to say idiotic.

Well the Building Inspector didn't agree with you. He was friendly and made suggestions on other things, but was quite happy with 150mm. No I do not always do things to the minimum, I would happily have gone thicker if anyone had suggested it.

 

[stuart45]

One of the reasons for going above the book min is that the bottom of the trench is unlikely to be dead level, so there would probably be areas where there was less than 150mm, as well as some that were thicker.

 

[CHarr]

Six inches was the prevailing standard at the time the house I'm extending was built (mid-1950s) and still was at the time its garage was added (late 1960s) and it is STILL the minimum standard required today.

I can't see the point in accusing anyone of being an idiot or of being an amateur for building on 150mm of solid concrete (assuming stable ground beneath). There have been no structural problems with my property in 60 years, and the main foundation was a six inch strip, three inches wider than the base of the walls, just two courses of brick beneath ground. It's fine.

I'd be happy to build to that standard today. How many of the hideous, modern shoe-box, crap houses being put together now in just a few days by 'developers' will still be standing in 60 years? Most Victorian terraces (many built straight off the ground, with no foundations at all) are still going strong, when the rubbish built in the 70s & 80s is already derelict.

The Emperor has no clothes!

 

[stuart45]

Victorian houses often had the footings spread out to take the load. Being built with lime mortar also helped accommodate any movement that occurred. Some of the better quality homes had a concrete footing.
Houses built with a harder cement mortar can't cope with movement as well as the lime built ones.

 

[andrew54]

One of the reasons for going above the book min is that the bottom of the trench is unlikely to be dead level, so there would probably be areas where there was less than 150mm, as well as some that were thicker.

Oh no, read my contributions above and mine were a minimum of 150. Yes I agree the trench will not be level, hence 150 or a bit more of concrete.

 

[stuart45]

The thickness is also determined by the width of the wall and the width of the trench.
For example a 10 inch wall in a 24inch trench would need a min 7 inches of concrete.
The measurement from the wall to the edge of the concrete is the minimum thickness if greater than 150mm.
Builders have generally used 9 inches of concrete in the past as a bit of over engineering in the foundation involves very little extra cost. An extra 3 inches means one less course of brickwork.

 

[CHarr]

Work on my extension (with heavy duty concrete foundations!) proceeds, and I'm trying to decide how to construct the internal floor. Posted separately in another forum: //www.diynot.com/forums/floors-stairs-lofts/construction-of-ground-supported-floor.383585/

 

[CHarr]

With the exception of fitting guttering, the external work is now complete. 1st fix gas, electricity & plumbing has also been done this week and we are ready to screed the floor and insulate the ceilings before plastering.

Untitled

• CHarr
• 6 Dec 2013
• 1

 

[noseall]

Why the fook was the guttering not fixed whilst the scaffold was in place?

Guttering is fundamental and is relatively simple to fix, yet does such an important job regards protecting the building.

Get it on, now!

 

[limerockconstruction]

Why the fook was the guttering not fixed whilst the scaffold was in place?

Guttering is fundamental and is relatively simple to fix, yet does such an important job regards protecting the building.

Get it on, now!

Especially given its taking the main roof too.

 

[Hugh Jaleak]

That downpipe from the main roof has been cut too short, you risk a damp patch on that wall. At very least it needs a shoe on the end to throw the water away from the wall!

 

[CHarr]

Why the fook was the guttering not fixed whilst the scaffold was in place?

Simply because one or two of the poles would have made fixing the guttering earlier awkward. Don't worry, it's going up today, and I have the 'luxury' of unimpeded access, and the ability to run my eye down the entire runs to check for alignment.

As for the existing downpipe, it hasn't been cut short, but is the original pipe, severed at one of its joints to facilitate the build. I'm replacing it from the top, with new brackets and a proper shoe.

Ironically, from the day we broke ground to the day the roof was covered, there were only two days on which there was no rain. Since the day the roof was covered, there has been just one brief shower. I could have collected all the water from that downpipe in a bucket!

This is the inside, on the day I took down the old external wall separating the former rather small 8x8 kitchen to make our new dining room. I'm very glad we deferred laying the floor insulation & screed until now, because it will make it so much easier to get the level across the two openings just right.

Untitled

• CHarr
• 7 Dec 2013
• 1

 

[Hugh Jaleak]

Fair enough regarding my comment over the downpipe, never know what may have been 'missed' so thought I'd point it out. Would be a shame to risk a damp problem for the sake of a couple of £ for a shoe.

 

[noseall]

Jeepers, that pillar is doing some work!

Did you under-pin it?