Although mortared stonework can cost up to twice as much as the same work dry laid, safety or aesthetic reasons make it preferable in some applications. Avoid using mortar as a substitute for fitting stone to stone or as an attempt to defy gravity.
For home improvement and landscaping, mortared stonework is more popular in dry, mild climates where the installation costs are lower. But considerations other than cost are also important. Even in climates without frost, the natural movement of the earth can, over time, cause the mortar to crack. Mortar exposed to weather deteriorates before the stone. Eventually it will need to be renewed for aesthetic reasons or, in some cases, to keep the stonework intact. Mortared stonework requires supplemental drainage, too. Water can’t move through mortared stonework as it does through dry-laid stone.
How To Mix Mortar
Use a wheelbarrow, mason’s mixing box or piece of plywood to mix your mortar. Combine one part portland cement with three parts mortar sand. Thoroughly mix the dry ingredients using a hoe. Form them into a mound with a well in the middle. Pour clean water into the well and gradually mix the dry ingredients with the water, working from the center of the mound to the edges. The amount of water will vary with the weather conditions and the amount of moisture in the sand. Measure the amount you use to get a sense of how much you need for each batch.
The mortar should be stiff enough to support the stones but wet enough to spread easily. The following can help you get the right consistency:
- If water seeps out of the mortar around the edges, it is too wet.
- Test-set a stone on a piece of plywood. If the mortar cannot support the stone with at least a 1-inch bed of mortar, it is too wet.
- Palm a lump of mortar in your hand. If it holds together and has a smooth uniform shape, it’s wet enough.
Mortaring Tricks and Techniques
- Mortar is irritating to the skin. Wear gloves and wash off mortar immediately if it gets on your skin.
- Mortar dries quickly. Work with small batches, no more than the amount you can use within an hour or so. Shade the mortar from direct sun, especially during midday, and cover it with plastic if the weather is hot or windy.
- Begin by working with an area large enough for two to four stones. Increase the size of the work area as your skill improves.
- Use tarps or cardboard to keep the foundation clean. Use plywood to distribute the load if you need to stand on freshly laid stones.
- Slow curing is important. Keep finished work damp by misting it and covering it with plastic for up to seven days.
- Clean the surface of stones that get spattered with mortar before the mortar hardens. Use a sponge and clean water.
- Mortar stains some types of stone. Check with a supplier, or test your stone for susceptibility to staining.
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