Fire bricks,Mortar

[atechnical]

I'm planning a firepit for the backyard. It will have a 5 foot circumference. The interior will be made of fire brick. Is there a particular kind of fire brick I should use and what is a good refractory mortar? Many Thanks

[thijsatteiltje]

Re: Fire bricks,Mortar

Hi,

it all depends on how durable it needs to be.
in my experience, for your averag backyard fun fire, which might get lid a dozen time per session, it doesn't really matter that much. Anything made out of bricks and cement will hold up, (as long as you'r not building load bearing structure, like a brick chimeny) and even expensive refractory mortar will produce cracks over time.

Real firebricks are dense, yellowish and expensive. if you can get those cheaply, go for it.

sometimes people sell normal red clay bricks that came out of a chimney as "firebrick". technically they are not, they are just good old honest red clay bricks but they are surprisingly heat resistant for occasional use and they are much cheaper and plentyfull.

A 5 foot firepit with a fire in the middle is not going to heat up the wall of the pit to furnance temparatures, so red clay bricks should be fine.

Personally i would not use modern concrete building brick (gray) as they are even less heat resistant (not to mention ugly)

As mortar goes, have a read on this
Refractory concrete mixing recipe | Heat resistant concrete ingredients for wood fired pizza ovens.

but my experience is that un less your building a forge to melled metal in , it is not that important. try to expose as little of the mortar seam as possible.

these two mixtures have always worked for me in backyard pizza ovens, rocket stoves and rumford fireplaces:

1-1- 3to6 clay-portland-cement-fine sharp sand
1-1-3to6- 0.5to1 clay-portland-cement-fine sharp sand -lime putty

(soak the lime power in water before hand to make putty)

adding lime putty to the mix helps by making it more sticky and plastic and easier to work with, but for straight walls you might not need it.

good luck.

[mrchipster]

Re: Fire bricks,Mortar

I'm planning a firepit for the backyard. It will have a 5 foot circumference. The interior will be made of fire brick. Is there a particular kind of fire brick I should use and what is a good refractory mortar? Many Thanks

Check your local fire department, we are not allowed to have a fire pit of that size in the Peoples Republic of Minnesota.

[thijsatteiltje]

Re: Fire bricks,Mortar

Oops,

updated the ratio of the mix. I made a mistake and the ratio that i originally posted is what I use for plaster and ferro cement, the kind you apply by hand and smear unto surfaces, so I need that mix to be a more sticky.

for brick laying mortar you need more sand. (1-1-3to6 clay-portland-sand)

I'm not an expert, also read this post: http://www.fornobravo.com/forum/f8/q...-mix-5868.html