Lime

Lime is an old material that used to be produced all over the UK for building. It was substantially replaced by cement in the mid twentieth century because cement was stronger, easier and quicker to use. Cement's strength also encouraged the type of building that we constructed to change. We could now build higher, faster and cheaper. However this came with a few downsides as well, most of which are overlooked by today's society and construction industry.

Cement is made at a much higher temperature and hence requires more energy to produce. This means that it is more carbon intensive - a growing problem, estimates vary, but between 7 and 10% of all carbon emissions in the world come from the production of cement.

Lime 'cures' by re-absorbing carbon dioxide and hence off-sets much of the carbon footprint associated with its production.

Lime is also breathable. This means that it allows water vapour through its structure. This might not seem to be important, but where we have cement rendered older buildings we have stopped the natural way of the building working but creating a non-breathable outer layer, this means that if any damp enters the structure (by cracks, rising damp, leaking gutters etc.) then the only way it can go is in, so you end up with damp problems in the house and in the main wall structure. This can cause immense damage. So if in doubt, use lime renders on any house built before the 1920's.

Lime can 'move'. The joints that you see in long walls made with cement mortar are there to allow the wall to expand and contract with temperature. This is because cement is not flexible. These unsightly joints are not required if lime mortars are used, since lime will allow for these movements. This is again very important in older houses, since many are not built on any real foundations and hence they move with the passing of traffic as well as the weather. This movement is not tolerated by cement renders and they will crack. This in turn leads to the damp and structural issues mentioned above.

Due to lime mortar being less strong it can allow bricks and stone to be easily reclaimed.

Any old mortar can also just be ground up, refreshed with some fresh lime and used again. Recycling at its best.

Lime does need a bit more thought and care. It cannot be applied when temperatures are less than 5 degrees centigrade for example. There are also different strengths and types of lime that you need to be aware of.

Lime putty is the basic starting point. This is ideal for external renders especially when combined with the correct aggregate. Lime putty should not be used with builders sand. For more information on the advantages of lime putty and also insulating lime renders visit www.limeworks.net .

Hydraulic limes come is different strengths. The strength of the lime should be matched to the strength of the material to be bonded. So soft stone / brick and internal plasters should use lower strength lime (NHL 2), external mortars should be an NHL 3.5 and for really exposed conditions where strength is an over-riding factor over breathability then an NHL 5 should be specified.

RDE can supply lime, but the main dealer in Lime in SE Wales is Ty Mawr Lime. If you need any product on offer from Ty Mawr please let us know as we can arrange an order for you that minimises on transport costs by sharing deliveries with others.