Now that we're nearing the end of work on the inside of the house, it's
time to start considering the outside. The biggest change there will be
a deck across the back of the house. I'd really like to have a hot tub
sunk into the deck.

I've looked around a lot, and there seem to be two types of commercially
available tubs. There are the GRP shell type tubs
(e.g. http://www.sundance-spas.co.uk/Spa-Showroom-Index.html), and
there are the timber barrel type tubs
(e.g. http://www.woodentubs.com/index.html).

I don't really like the idea/look of the GRP ones at all. In addition,
the bigger ones get very expensive, and most of them are a little on the
shallow side.

I like the timber ones, but they tend to be lacking in insulation. I'd
like a well insulated tub.

So I'm thinking about building one from scratch. The water heating and
circulation aspects I'm pretty happy with. What I'm not sure about is
the actual construction and waterproofing of the tub.

I can think of two main ways of doing this. Timber frame faced with
marine ply which is then tiled, or concrete block which is then tiled.

One of the main requirements will be to insulate the tub with 100mm
kingspan. I can see how it's achieve this on the sides and bottom of the
timber framed version, but I can't quite picture how I'd do it on the
block version, without doing a double skin of blockwork. One option is
to not insulated, and just use aerated blocks, but I haven't looked at
the U values yet.

As far as size goes, I'm thinking aound 2.5-3m long by 1.5-2m wide, and
about 1m deep. If done in ply this will be rounded to nearest board sizes.

So, any thoughts? Anyone done/seen/heard of anything similar? How was it
built? How was it insulated? How would you do this?


--
Grunff