A self build house project diary
by Oliver Cannell
Thursday 19th June 2014
(published/edited Wednesday 2nd July 2014)

Going down some more, before anything can up

This week has seen the first of the foundation trenches being dug.

It's been an exciting couple of days on site, Thursday and Friday this week, as digging of the foundation trenches has begun. Nearly everything that has been done to date has been either to clear out soil to make way for the house; build supporting walls for the boundary, or generally get things prepared for building the actual house. But now we have definitely started works for getting the house itself underway. Obviously we are still digging down... but once these trenches are done we can aim skyward.

Even from the few trenches that have been dug so far, there is so much soil coming out of the ground - which has to be taken away - and there will be even more next week, what with all the remaining trenches to be done. On average they are about a metre deep, but in some places they are deeper, to accommodate the mass of concrete involved, which will support the structural steel elements for holding up the roof.

As the shape of the house is irregular, there needs to be some steels which will enable the roof to be formed - and to make it strong enough to withstand the wind forces calculated.

Structural design and engineering

The Structural Engineer has supplied us with numerous calculations for this part of the build and there is going to be quite a lot more steel work involved that originally thought. This seems to be a standard for this project now - everything requires more than originally thought!

Additionally, we've had to modify the design of the external wall blockwork, so that it uses 140mm thick blocks, instead of 100mm. This, again, means more expense - although the benefit will be great thermal efficiency, so it should be cheaper to heat the house in winter.

Forming the foundations

Along the back of the plot, the significant structure for the retaining wall will be formed at the same time. Steel bars and mesh will be cut, formed and tied together to build a cage, which will sit along the whole foundation (at the north end) as well as extending into the foundation of the house itself. This has effect of providing extra support for the retaining wall but utilising the house foundations as an additional load bearing structure.

Another benefit is that we can position the house closer to the retaining wall (700mm), as both structures share the same foundation. The mass of steel and concrete involved enables us to do this, but it's going to be a pain-staking and time consuming task to build the steel cage, before concrete can be poured in one hit.

It's great to see the footprint of the external and internal walls of the house starting to take shape at last.

Next entry: Virtual Tour - foundation trenches all dug (Friday 4th July 2014)

Previous entry: Time to get this show on the road (footpath) (Thursday 12th June 2014)

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