The big ground floor slab pour

Just back from France to see the pouring of the ground floor slab.

Here as elsewhere in this project we have gone for a simple, robust and cost effective solution: an industrial polished concrete floor. The cost effectiveness comes from simplifying what is normally three layers (concrete slab + screed + floor finish) with a single concrete layer which is polished to form the finished product.

The only problem with this system is that there is no margin for error which puts pressure on the craftsman to do the job perfectly first time round; this includes making sure that all services are laid correctly into it before the pour.

Here you can see the space prepared for the pour. The orange material is a thick layer of insulation (100mm) with upstands to stop cold bridging with the walls. The various blue and black tubes are ducts which will be cast in the floor in which cables and pipes for the electricity, data and plumbing will run. A metal mesh covers the space to resist cracking.

Here is the amazing "scorpion machine" which squeezes the concrete where is needed.

The craftsmen at work. It is a fascinating thing to see as the concrete is porridge consistency and they have to get it at the perfect horizontal level in that state. They guide themselves with a laser system (on the tripod) which makes a sound when the guide (which is used by the man on the right) is at the right height. As the concrete sets quite fast, it goes very fast. There is no margins of error; it simply cannot be re-done.

Here is the result before polishing. The end product is mirror like and a bit lighter in colour. I had to leave before they started the polishing which starts a few hours later once the concrete has set. More pictures to follow for final effect when I am next there in 2 weeks.