[Greenbuilding] Type of concrete for radiant floor

[Chris Green]

Richard Hakim wrote:
> Hello.
>  
> We are building a house on the coast of the Pacific North West.  We are
> putting in a hydronic radiant floor in 1.5" of concrete.  Being remote, I
> need to have the gravel and cement for this concrete trucked in and then
> hand mix and pour on site.
One option that might be considered is to have the sand, gravel, and 
portland cement loaded into the mixer truck, and bring it in dry. Add 
the water at the building site. I heard about one project in a remote 
location north of Squamish/ Whistler Mtn.,  where they brought in two 
truckloads or deliveries for a job, and both times the mix was already 
'going off' when the truck arrived, so the engineer on the site rejected 
the mix. The loads were dumped. The third time they added the water at 
the job site.
You might have to search around for a supplier who will do it this way.
>   
>  
> I am trying to figure out the type of concrete to order for my radiant
> floor. 
Ordinary portland cement based concrete is what we use here in the 
interior of B.C., but our floors are 3 or 4" thick. We use 5/8ths rebar 
on 2' centers, with poly and rigid insul underneath. The house we've 
just closed in has 2 1/2" of rigid insul underneath the floor. Keeps the 
heat from being absorbed by the rock the building sits on. If it hadn't 
been insulated this way, the rock mass would take years--perhaps even 
decades or centuries-- to warm up to room temperature.

If you opt for the dry mix to be trucked in, be quite diligent about 
providing a flat surface under the  floor, well compacted. The closer 
you get to flat, the better you can calculate the amount of concrete 
you'll need.

Oh, yes. Another delivery method used in remote locations, but a very 
costly one, is to have the concrete brought to the site in dump buckets 
underneath helicopters. Pricey beyond belief. at $600-1,000+ an hour for 
the 'bird, money you could use to hire a lot of labourers for the day. 
Also helicopters use a lot of fuel.

Cheers,

Chris Green.