Lightweight concrete first floors?

[Hindhaugh]

I am in the process of drawing up plans to renovate an existing old cottage in 36 that has an existing traditional beam and earth first floor, the upper floor (loft space) has access from a domer type door at the front of the cottage this would have been used as the hay loft ect.

I will be removing the existing earth floor, replacing the existing ceiling beams with 15cm square oak beams as original. THE QUESTION: I could simply put an insulated timber floor over these beams but it appears that it is possible to cast a lightweight conctrete floor on top of ceiling panels placed over the oak beams. The timbers are supported with props etc whilst the new concrete floor is cast. From the ground floor it looks like a traditional floor with beams etc but it has the benefits of concrete. Anyone out there with any tips or experience of casting this type of lightweight concrete floor. Do I require special concrete etc - note this is not a beam and block system I am describing - its a one piece slab. The idea is shown on pages 78 and 79 of 'How to renovate a house in France' but no great detail is given.

Thanks for anticipated advice from you old hands!

JohnH

[LesFlamands]

We've used a product called 'Granuland' which is basically wood chippings treated with a flame retardant. Mix with cement as per instructions on the sack to give the weight of concrete required. It does take a long time to fully dry out so you can't really put any other wood or plasterboard in the building whilst it is drying.

There are other products available using both polystyrene and vermiculite as the aggregate. With all these products you need to use the 30mm reinforcing mesh.

[Stocky]

On moving our 2mtr by 2mtr bathroom to one of our bedrooms we needed to raise the bath 10 cms to allow a good water run off.  We asked the Carpentiere for a quote for a wooden platform.  He took one look and said that it would need a concrete floor.  As this was on the 1st floor we were astounded but when our Plasterer cam rounf he said no problem.  The lightweight concrete contains polystyrene rather then sand and is doing the job required.  We could probably lift the 2mtr sq block.

[La Guerriere]

There's an article in "Restaurer sa Maison" Jan / Feb 2006 "Creer un Plancher Mixte" which might help . If you can't find, send me a PM and I'll send it to you.