Any self performed project must self appraise ones own skill for carrying out the project. What skills must I learn and at what price? Rework, unacceptable finished product? Masonry skills are being lost because of the high cost of the labor component and competing lower cost alternatives such as glued on veneer stone. Stone has wonderful earth energy and will give any structure and space a unique special connection with the earth. Concrete is also a special material similar to natural stone. Concrete is a man made conglomeration of many stones bound with cooked limestone (cement). My approach to building with stones is whenever possible use natural full size pieces, not veneer, combined with concrete to create a less skill required finished result. Laying loose pieces of stone on concrete formwork and backfilling with concrete creates a strong monolithic composite structure with the look of pure stone. Concrete backfill can be accomplished with traditional casting or shotcrete (gunite) methods. In the Hobbit house I used mostly shotcrete sprayed directly on the stones to create a thickness of 4-6".
Excellent bond is easily achieved between well consolidated concrete and clean stones. In building structures like the hobbit house I have found this procedure to be fast and always excellent aesthetically when the forms are striped and the joints are pointed with mortar. The only masonry skill required is choosing a stone and placing it on the the formwork. On vertical surfaces the stones are held in place with tie wire. The tie wire is placed around the stone and through small holes drilled in the form work. In earlier projects I used dirt or sand placed between the stones prior to placement of the concrete backfill. This prevents the concrete backfill from coming through the joints between the stones and filling in front of the stones. This method works well on horizontal surfaces but not so well on vertical surfaces such as walls. I have found using spray foam out of an aerosol can with a tube works excellent. After concrete backfill and formwork striping, the foam is present in the exposed stone joints. The foam is dug out with a screw driver. In the case of overhead work I would still recommend sand or dirt. Once the joint is cleaned of foam or dirt a masonry mortar is tooled into the joint similar to a repointing procedure. Repointing procedure involves mixing standard masonry cement and mason sand in a stiff consistency and packing the mortar into the joint openings. The key to professional looking joints is to allow the mortar to stiffen, which may take a few hours and then with a jointing tool finish off the joint. When complete a muriatic acid ( home depot) wash cleans up the stone of any smeared mortar on the stones.
