CARING FOR YOUR LIMESTONE
In general, limestone is a very durable building material as long as its fixed correctly and given proper care and attention. With good building practice, you can expect your limestone to mellow and mature nicely. With today’s technology, superior materials, and increased knowledge about preservation, it has become easier to keep limestone in good condition. Here are some guidelines and recommendations to help you.
PROTECT STONE FROM COLD WEATHER
Stone is very susceptible to weather damage until it’s laid. If your stone is being delivered during the colder months please ensure it is protected from the weather during storage. A minimum of two layers of insulating material covered by strong polythene or tarpaulin should be used. This will protect if from freezing weathers and frosts, and keep water out. The delivery packaging itself is not considered suitable for winter protection. Part-built walls should be covered with at least two layers of heavy sacking material and an outer layer of robust polythene or tarpaulin so that water doesn’t get in.
At ground level and especially in the garden, your limestone needs protecting from rising damp. This can be done with either a plastic membrane, or for internal projects, by making sure that a damp proof course is in place. Where a wall has a common boundary with a building, you will need to ensure a membrane separates the two structures to prevent passive damp.
Most limestone stays structurally sound with one or two faces to the weather, so long as there are no other forces at work, such as rising damp or water soaking from the rear or above. The main reason for the failure of some limestone is water saturation due to poor building practice which, in turn, causes frost damage. For example, hard landscaping to the ground surface next to the natural stone. A drainage gap should be provided for rainwater to drain. Where this is not possible, for example where you have steps, a ‘fall away’ from the stone face is essential. Stone failure due to water saturation can also be caused by an insufficient coping stone. Copings require a sufficient overhang (minimum 50mm), and drip grooves, to help stop rainwater penetrating the stone.
Chemical treatments are widely available to help protect your limestone from the elements, which also allow the stone to breathe and prevents trapped moisture. Because stone is a natural material, please do seek specialist advice before you buy any manmade products.
AIR FLOW AROUND THE STONE
It is essential that all limestone exposed to freeze/thaw conditions has sufficient air flow to the rear of the stone. The cavity should be clear of groundwater, mortar, debris and insulation. Weep holes sited at ground level and above all lintels will often provide sufficient ventilation. Where insulation batts are used, a minimum air gap of 25mm should be maintained.
USING STONE INTERNALLY
Using stone internally has become increasingly popular, for example flooring, staircases and fireplaces. The risk of rising damp is eliminated by a damp proof course and your stone will be protected from the elements by the roof and relatively constant internal temperatures. Please speak to us about the best way to install, preserve and care for your limestone floors and fireplaces.
For further information about working with limestone please see our ‘Working with Limestone – Good Building Practice’ guide.