Getting House Construction Started
Assuming planning is finalised and approved, setting out can begin. This is outlining the buildings footprint by driving pegs into corners and marking the proposed walls out with survey line spray.
Within the plan all the load bearing walls should be marked, and the width of the trenches also, the depth will have to be determined when the ground has been broken into.
The trench work is usually dug by backhoe or mini digger, as is the back fill.
It is generally the building inspector that determines the depth of the trench. Provided the soil has good load bearing and is firm, such as chalk or clay, the standard minimum depth is 1 metre.
Where this is the case, trench fill foundations are normal. Concrete is poured into the trench to within 150mm of the top, saving time and effort.
Because the sides of the trench support the load as well as the base, where the soil is not as compact, strip foundations are used. A layer of concrete is poured in the trench, a min. of 250mm, and build up on this with blockwork to the ground level.
If the site slopes then the foundations have to be stepped to keep them level. Steps need to overlap at least the width of the trench when concreted.
Should the ground prove particularly difficult to stabilise, deeper trenches must be dug, however, the limit, for practical, economical and safety purposes is around 2.5metres, after which piling is usually used.
Piles, like large tubes are driven down to stable ground and concrete poured into the hollow column and the whole foundation gets topped with a ground beam to build off.
With digging machinery onsite (Hanlon CASE are leading providers of construction machinery) it is as well to install the underground drainage at this stage. The levels are vital in laying the drainage system.
The fall, or gradient of the run ideally is 1:40, but modern plastic pipes can tolerate less, though digging to correct depth for all the system can avoid having to build parts of it up with large amounts of aggregate.
The trench must have at least 100mm of gravel initially, as bedding for the pipe and surround material supporting and protecting the pipes at the required fall.
Utilising the drainage trench for other services is good practise, laying water, gas, electric and even fibre optic cables in position at this stage saves time, money and intrusion, having the actual services connected later.
The drain system should be pressure tested, and the building inspector consulted before backfilling the trenches, to ensure connections and runs are sound.