BASEMENT TANKING

CAVITY DRAIN MEMBRANES
Where a Cementitious Tanking System (cts) is to be installed or specified to create a dry internal surface to a basement or a under ground wall structure. The walls to receive the system must first be in a dry enough condition to accept the cementitious specification. This is normally a multi-coat render system incorporating a waterproofing slurry, and is keyed to the fabric walls by raking out the bed joints and removing any painted wall coverings, on occasions during the preparation works, physical water will enter through the walls, this normally dose not present its selves as a problem and is initially solved by either plugging the steam of water with a water plug, or by diverting water through a pipe work drainage system which is physically pumped out of the building throughout the course of the works until the final plugging can be achieved.

For a perfect effective system to work, the (cts) and the structure must be able to with stand the forces and stresses exerted on it by hydrostatic water pressure, this system would have to be designed by a structural engineer, as with any system that is designed to prevent entry of water into a building fabric, there is always the risk that in preventing the consequent build-up of water, the pressure may move to another area which was not previously effected.

Our experience at ISCA Preservation shows that it is not always possible to construct on site the almost laboratory specification required to construct the (cts), any failure (even a pin head defect) would lead to a guarantee claim. More anxiety, damage, and costs.

The Cavity Drain Membrane System (cdms) accepts that water pressure and the ingress of physical water will continue to penetrate the fabric, it is not in conflict with hydrostatic pressure, consequently there are no undue forces or stresses.

British Standard 8102 (Protection of Structures Against Water from the Ground) has a design criteria to control both the effects of penetrating ground water, and water vapour. The manufactures of these membranes have a very clear design specification and technical support systems that allow specialist contractors to achieve compliance to the British Standard in the most difficult of situations with relative ease. Our supplier, Triton Chemicals is at the forefront of such developments and has a very comprehensive range of ISOLA products. The Basic principles of the (cdms) are to provide a sealed waterproof system, a equilibrium of water pressure, and the disposal of water.

Here at ISCA Preservation, We can design a fully sealed membrane system most suited to the building.

The effectiveness of any specification must always take into account the ability to discharge water, any system that relies on the existing drainage must be checked for suitability or drainage channels around the perimeter can centralize the water to a pump. In all cases regular maintenance is essential.

In order to reduce the amount of water ingress problems entering into the structure, the external fabric should be maintained.

GUIDE TO MAINTENANCE
We draw your attention to the defects itemized below. These are for guidance only and do not constitute a structural survey or any part thereof. A builder should be engaged to attend to the repair work as soon as possible. None of the items listed below will have been included in our Quotation or Estimate
External and Interior Plumbing:
-faulty gulleys. Gutters, down pipes, drains, internal water leaks

External fabric

- Cracked cills, lack of cill throats, cracked render

- Spalling and decayed brick/stonework, facings, plinths

Apertures

- Faulty window and doorframe sealant

- Rot in external joinery, window frames, and doorframes

- Chimneys open/capped without ventilation

'Bridging' problems

- Flowerbeds, paths, steps, adjacent constructions covering or too close to the damp course level

- Garden walls, fence or gateposts attached to the property

- Plants and shrubs growing too close/over the walls

Sub-floor ventilation

There are no restrictions on how the walls and floor finish can be finished upon the installation of the membrane. See projects for examples.

Project 1 (click on image for case study)

Project 2 (click on image for case study)