Starting the stonework

I've finally started laying some stonework for our fireplace. It's slow but fun! My original thought was to have a professional mason lay up our fireplace and chimney with blockwork, and then as time permitted I would go back and face the blockwork with stone from our farm. But as I'm learning with this house, it really pays to think about your plans and to see if there isn't a simpler, cheaper solution before you dive in. (or maybe all this "thinking" gets me in trouble - which is it?)

Although a blockwork fireplace would provide a solid and plumb guide for stonework, it would impose the additional constraint of using stones of a somewhat consistent thickness. (think "bricks" or the fake glue-on stones that you see in restaraunts.) I recently came upon the seemingly credible idea of pouring a fireplace from http://www.rumford.com/concrete.html, and that has intrigued me. I've also been fascinated with slipform masonry, but the results of slipform masonry seem... sloppy. What I've decided to try is to lay up my stone first, mortar it slightly so that it looks like drylaid stone, then pour against the backside of the stone slowly, in short lifts - bracing the stonework of course against the pressure of the concrete. Maybe it will work. I'm going to find out.

These pictures show are the results of my dry-stacked prototype so far (no mortar). The large picture at the beginning of this post shows the view of the fireplace structure from the 3rd floor loft. The fireplace faces east. Backing up to the fireplace, facing west, is an alcove for the wood cookstove. I will use block (as shown here) with poured cores or concrete forms for the cookstove alcove. Facing south will be the wood fired bread oven (not shown) and directly beneath the bread oven will be back to back wood storage alcoves for the kitchen and greatroom.

The idea, to state it another way, is to build the perimeter of my fireplace structure with stone, brick, or even CMU - whatever is most appropriate, brace it all, and then pour the inside of the structure full of concrete.

The last picture shows the backside (inside?) of my stonework. As you can see, stones of varying thickness can be readily acommodated, and the uneveness of the wall should help to bond the stones to the structural concrete that gets poured behind them. I have a book on stonework (sorry I will provide a reference later) that is a proponent of a similar approach to stonework.