Chris
The enclosure is six foot, by four and a half foot.
Im not sure of the hight, but it is probably just under three foot or so.
Cost wise I was lucky, as almost all of the materials used were given to me as spares left over from building work that my friends had done.
As for how many newts it could hold, I couldnt say, but in the article on outdoor enclosures in the book amphibians in captivity, it gives the guideline of 0.15 sq m of ground space for an amphibian the size of a fire salamander.
I hope this helps.
MORG