!#7# Basement Waterproofing by the Drained Cavity Method - How to Avoid the Problem of Limescale Build Up

!±8± Basement Waterproofing by the Drained Cavity Method - How to Avoid the Problem of Limescale Build Up

This article advises on a few simple ways that this problem can be eliminated, or at least minimised.

Sources of Limescale.

Limescale comes from two main sources - it is naturally present in hard water areas where there is a lot of chalk in the ground and from new concrete, which is present in large quantities in cellar conversions, which have new underpinning and / or a new concrete slab.

How to reduce limescale build up

If you are having a lot of new concrete, use a retarder - such as rugasol - on the surface of the freshly place concrete and then remove the cement paste from the surface before it sets with a high pressure jet washer. The retarder can be placed inside the shutter for shuttered concrete. This removes much of the free lime that would otherwise dissolve in the water.

Include inspection / clean out ports in the channelling system so that they can be flushed out as part of the maintenance programme.
Use a channeling system with curved corners rather than right angled ones to make the flushing process more efficient.
Use a sump chamber with a wide grating rather than small holes in the side and mesh gauze filter on the outside, which will then be accessible for cleaning.
Use a flexible membrane, preferably without dimples on the wall, rather than a semi-rigid one with dimples, this way the small cavities between the dimples cannot block. Note: - the use of non-dimpled membranes in drained cavity systems is generally poorly understood, largely for historical reasons (before the advent of perforated sump chambers and under floor channelling systems the dimpled membrane was the only conduit for water to get into the sump but with the right sump liner and channelling system the dimples are no longer strictly necessary).
Instruct the installer to carry out a service inspection more frequently than the normal once a year; six monthly would be a good idea at least for the first couple of years whilst the concrete is still highly reactive. Have a multi-pump system rather than a single pump system. A twin main and a battery back up is the most comprehensive solution. If the first mains pump becomes coated in limescale, as can happen if the pump is working a lot and gets hot, then the second mains pump will remain free of limescale if it is configured in such a way as to only come on in the event of a failure of the primary mains pump.
Make sure that you have an alarm system, which will indicate when the back up pump comes into operation.

Limescale can be a nasty enemy of the drained cavity method but by implementing all the tips described above the risk of it posing a problem is practically eliminated.

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