A quick guide for using stone to build your house

Stones are a strong resource, sometimes used in house building. Here's what you need to know about stonemasonry, to help you decide if it's the right option for your house.

You can tell a lot about stone even if you do not know what type it is. Always compare its weight, texture and appearance with other stones.

• Building stone is heavy and resists moisture. Break open a sample with a sledgehammer. It should be difficult to fracture, breaking into uneven, rough-textured chunks.
• Stone that crumbles or splits ­easily along a flat plane is probably weak, porous and unusable.
• Few building materials match the character and air of permanence suggested by a wall of stone.
• The seeming randomness of this natural, unfinished material is, in fact, carefully calculated to provide a mixture of shapes and textures.

• Field stone is collected from loose surface rock. It is rough-textured and worn from the passage of time and exposur­e to the elements.
• Quarried stone is cut in regular shapes from ­massive outcrops. Its freshly-­exposed surfaces are polished, sharp, clean and regular.

The skill of the stonemason involves selecting the proper stone to lay in a particular place and then adjusting it to fit securely, either by shaping the stone or by filling around it with smaller rock fragments called shims.

• The first stone structures were dry — they were built without mortar.
• Later, clay, lime or cement was used to hold the rocks or stones in place.
• In either type of masonry, structural integrity depends on the same two forces: gravity and friction. The mason must use these forces to create enduring stonework.

Whatever type of masonry is employed, whether it be dry masonry or mortared masonry, the natural forces of gravity and friction are employed as much as possible to make a wall as solid as possible.

• For gravity to have the desired effect, keep the stones' bedding surfaces horizontal or canted slightly inwards towards the centre of the wall. Maximize friction by creating as much contact between stones as possible.
• Follow the old rule "one over two and two over one" so that each stone rests across at least two stones beneath; gravity then locks the stones together and unifies the structure.
• Maintain solid bedding surfaces by shaping or shimming any stones that fit poorly.
• Shaping is done with a hammer and chisel.
• Shimming is done by inserting small pieces of filler rock in spaces between stones, thereby providing support and increasing surface contact.
• However, do not use shims as wedges to hold stones in place. If you do, the wedged stones may eventually work free.
• The best use of shims is for levelling and stabilizing the bedding surfaces, always with the goal of keeping them as horizontal as possible in order to make the fullest possible use of the force of gravity, which pulls straight down.

Keep this guide in mind and learn about stone masonry to help you determine if it's the right choice for your house.