The Royal Household, Kensington Palace

Harrison Waterproofing is an authorised and recommended installer for the two leading methods of internal waterproofing systems in Britain.

Where the water pressure is particularly high, where noise and dust are likely to cause concern or where it’s required to retain the existing features of a building, we generally recommend a Cavity Drain Membrane (CDM) system, to control damp or water ingress.

With a CDM system any moisture is allowed to pass through the masonry. Thereafter it’s controlled by the use of a waterproof, ‘eggbox’ design, High Density Poly Ethylene membrane, attached to the masonry.

This was the case when we waterproofed stately Kensington Palace. We first begun to manage the water flowing through the cellar walls in the underground vaults.

Once an area is waterproofed, we can either render directly on to the CDM or provide a ‘dry line’ plaster finish.

Where there is not a gravity fed option, the Cavity Drain Membrane system is supported by pumped system.

Many architects now recommend the installation of a water collection channel, pictured right, which can be bedded into a preformed channel at the floor/wall angle. Holes in the channel wall allows water to ingress at this point to drain away to a sump. Rodding eyes are available to allow maintenance and inspection.

The Oakmere House

Of the two types of rot, Wet Rot is the less serious. This is because it does not spread through masonry and its growth is quickly eliminated when moisture is removed.

However, Serpula Lacrymans, i.e. the true Dry Rot fungus, is extremely malignant and will spread even through thick walls in search of timber to attack. It is invariably caused by poor building maintenance. If you suspect Dry Rot, to avoid extensive damage, we therefore recommend you contact us immediately.

The first steps Harrison Waterproofing take to treat dry rot, is to locate and remove the underlying source of moisture and remove all effected timber. We will then apply Fungicidal treatment to infected masonry by drilling, irrigation and surface spraying.

Epoxy Resin Repair

During the last 30 years Harrison Water proofing has developed a range of tools and techniques that enable us to confidently tackle almost every type of timber problem. Where faced with joist end decay on major or bressumer timbers, that are required to be retained, one of our fail-safe techniques is the use of Epoxy Resin Repair. This provides a repair that is actually stronger than the original timber!

Additionally, because careful application can replicate the host timber colour and grain, this type of repair is also popular where, for aesthetic reasons, it's required to retain the original timber profile.

One of our recent projects was restoring a 100 year old bandstand in Ruskin Park, South London. The pictures bottom, left & right show the mixture of new remoulded timber, fixed by carbon rods and epoxy resin, into the sound original wood.


Gunite is a sprayed-on concrete material that's commonly used either to create a robust lining for otherwise fragile structures, or with a framework grid, including steel reinforcing rods (rebar), to form the walls of a swimming pool. The tough finished lining is created by combining a dry Gunite mix with water just before spraying, (the dry process).The Gunite mix is stored in a hopper and fed by compressed air, through a delivery hose, to a nozzle where it's mixed with water immediately before spraying. The application is quite an art as one false move often means that blockages will occur. Our experienced Nozzle Operators are therefore always in demand.

The pictures bottom, left and middle show the Gunite being sprayed from the mixing nozzle on to the framework grid of a luxury indoor pool that we constructed in leafy Hertfordshire. The Gunite mix can be seen to be bonding to the rebar and building layer upon layer to form a tough structural shell. A benefit of this form of design is that all the plumbing can be installed prior to Gunite application.

In addition to pool forming, today Gunite is used in a vast range of applications including tunnel lining, pipe lining, pile lining and fire protection. Here at Harrison Waterproofing, the most common demand is for us to re-enforce existing underground earth retaining wall structures prior to waterproofing.

Wellington Arch

A Cementitious waterproofing system maintains a dry environment, in an underground area, by creating a physical internal barrier to damp and water. For this type of system we are authorised and recommended by industry product leaders, Sika Ltd. During this relationship we have installed the Sika water-proofing system in basements, lift pits, underground tunnels, bridges, reservoirs and swimming pools. As such, we welcome tenders for any size of contract.

The first step towards a successful Sika system is adhesion and it’s essential the substrate is suitably prepared, either by Scabbler or Bush Hammer, prior to work starting. Thereafter, if there is any likelihood of movement, we also recommend the use of combiflex movement joints around wall / floor joints. False economies here can lead to expensive problems further down the line.

Thames Wall, Rainham

Firstly, we had to cut away any affected concrete and treat the reinforcing bars.

We used specialised flexcrete repair mortar to re-instate barrier wall, stripped out the failed mastic in the movement joints and then finally the re-instatement of new expansion movement joint.