Fibre cement base for hearth ? Newbie Forum Discuss Fibre cement base for hearth ? in the Good Background Information forums; There's nothing better than chucking a brick in the middle of a pond and seeing where the ripples go! Admittedly ...

[Nev Grady]

There's nothing better than chucking a brick in the middle of a pond and seeing where the ripples go!

Admittedly I was very concerned about my design using 2" pavers but after consulting a couple of friends, one's a builder and the other a structural engineer, I decided to go ahead. They recommended keeping the weight down so I've used a 2" layer of high density ceramic insulation (Insulfrax) on the dome, on top of which is a 4" layer of high efficiency mineral (Rocksilk) insulation. This is covered by a layer of lightweight plasterer's mesh and then an inch of waterproof render. The concensus of my consultants was that the insulating slab should spread the weight and if problems do appear it's not too difficult to insert some supporting beams

If I'm still around in 10 or 20 years time and still have the strength to wield a pizza peel then yes, let's have this debate again!

[dmun]

The main appeal to me was that I can't lay blocks, so avoiding mortar was good, and the large size means I can get the required height easily and they are very stable.

Laying a proper, mortared, concrete block wall is a non-trivial exercise. The mortar falls every which way on those thin edges, and getting them lined up and level is harder than it looks. Dry stacking was a technique designed for amateurs: if it doesn't look right, you just stack them up again. Remember: many of our builders have never picked up a brick or mixed a tub of mortar before starting this project: we don't want them angry and discouraged before they even get to the firebrick stage.

[Neil2]

"Over-engineering? "

One comment I have never heard on a construction site:

"Damn, I must have put too much rebar in that slab."

[Nev Grady]

That's what the intrepid oven builder said as his oven sank slowly into the ground........

[Lardylad]

Nev,

Thanks for your comments - good to see that the Brits are managing to live the outdoor lifestyle as well !!!
You mentioned waterproof render. My oven will not be under cover, so the render needs to be waterproof. Did you buy render off the shelf that's waterproof, or is there an additive that you use ?

Cheers,

Lardy