Building with Stone: Slip-Form Construction

Learn the basics of slip-form stone construction.
May/June 2004
http://www.motherearthliving.com/Green-Homes/2147484657.aspx




Slip-form stone construction has been used for years; architect Tim McCarthy adapted his own technique from those of New York City architect Earnest Flagg, Frank Lloyd Wright’s Taliesin West, and back-to-the-land pioneers Scott and Helen Nearing. Slip-forming lets the builder create a flat or plumb stone wall without using masonry skills, making it less expensive and more accessible to the layperson. “I believe slip-form stone will become more popular as the natural building wave matures,” says Tim.

Single set of forms

Previous slip-form systems used a double set of forms that leapfrogged one on top of another up the wall. Tim uses only one set of forms to contain stones until the cement dries, then he simply moves them up to continue building. This method:

• Saves the cost of a second set.

• Reduces the amount of time before you can observe your stonework.

• Gives quicker access to the partially cured wall, which allows cleaning and “pointing” the wall while the cement is still “green.”

Guides for the forms 

• Guides are lightweight, and easy to build and set up.

• Guides allow you to build a tapered wall if desired. Angling the wall increases overall stability and reduces the amount of material needed at the top.

• Guides stabilize insulation on the interior side of the wall. The rigid insulation acts as an inner form to brace the rocks.

• You can add horizontal boards so that guides double as scaffolding.

• If you’re using straw bale construction as insulation, guides provide support for a temporary roof to keep the straw dry.

• One set up can be used to build both the footing and the wall instead of setting up the wall after the footers have been poured.

• Guides provide a permanent reference point and template for wall construction.

• A guide system is stronger than wire-tying the forms together, allowing the use of large batches of concrete from cement trucks.

• For detailed instructions or to download a sample chapter from his slip-form stone building manual, see Tim’s website.