With the demolition complete it was now onto the real business of getting on with construction rather than demolition work.
Derek first built a house with a basement in Norway in 1982. It was on a sloping site and built like most properties at that time.
The site was dug out and cleared of debris, which was mostly partially solidified scree material. A thick layer of drainage stone was laid out across the site. Basement walls (about 250mm thick), with reinforcing, were cast directly onto this layer of stone using crane and hopper. Shuttering elements were hired for this work. On the outside of the basement walls, in the areas to be backfilled, a stiff impermeable sheet of plastic was rolled out. This sheet was moulded into studs to allow movement of any water which penetrated the sheeting joints. The sheets were held in place by more drainage stone which filled the cavity between wall and the dig. Before this stone was dropped in a land drain was laid around the outside of the walls and level with or just below the foot of the basement walls.
The key to this system being effective was to have good drainage, the 2 essential components being 1. Somewhere for water to go to, and 2. The ability for water to move freely around the outside of and below the structure. There did not seem to be any requirement for a concrete base slab.
Below are Derek’s thoughts regarding the advantages and disadvantages of constructing a basement
Advantages of a basement:
- extra living space without the use of a large part of the building plot.
- good storage at fairly constant temperature, good for fresh food, not freezing.
- can be developed as a separate living unit.
- ideal space for swimming pool, snooker room, film studio, playroom, storage room, plant room, utility room. We have our entire boiler and under floor heating systems in our basement with easy access to all pumps and tanks.
- can be developed at a later date when more living space required, and more money available (need to get down the cost of building a basement in UK)
Disadvantages
- a lot of earth movement required.
- not always easy to keep dry.
- needs structural strength as forms the foundation for rest of building.
- expensive if you have to have a thick floor slab. I used 29 cubic metres of strong concrete for a 250mm thick floor slab, and I had to build a 400mm solid block and reinforced concrete infill wall around the whole structure.
- environmentally very unfriendly. Think how much cement went into this.
How to keep dry – see notes on images above on :
- good drainage is essential, using drainage stone, land drains, impermeable membranes, paint on DPM.
- don’t rely on tanking to keep water out.
The bit we have all been waiting for - the oak frame is on its way.