In the TV show ‘Help! My House is Falling Down’, recently aired on Channel 4, Delta Membrane Systems solved a particularly difficult problem with an unusual construction technique.

A residential town house in Brighton was in need of restoration. However, a method of construction peculiar to that geographic area – known as bungaroosh – proved to be a real challenge to all concerned with this project.

The elevation to the rear of the house has an exterior ground level somewhere about 600mm higher than the first floor level of the house itself. The entire ground floor of the house is below exterior ground level.

Bungaroosh is a mixture of flint, rubble, old bricks and lime mortar. In fact, anything solid could, and would be, thrown into the mix including lumps of timber and chunks of chalk.

This technique was used in the 18^th and 19^th centuries, and was carried out in ‘lifts’ using a formwork system. It was usually covered in a smooth lime render, then lined out to replicate stone, and then painted.

However, it is little surprise that bungaroosh is unstable, and it has the added disadvantage that it cannot have a chemical injection damp proofing because of the haphazard nature of the construction and the questionable quality of the materials within the construction.

Matt Baker, the producer and director of the programme – made by Red House TV for Channel 4 – takes up the story: “Initially we thought that this job would be little more than redecorating ... but then we were talking about the roof being removed, and the real risk of the bungaroosh getting wet and losing its structural integrity. This started off as a small cosmetic job, and then quickly became a major structural project”.

“Our structural engineer on the show described as being like a woolly jumper ... if you started picking at it, the whole lot would unravel,” Matt states.

Delta came to the rescue with a solution that involved Delta-PT (including the new Slimline version). This special high performance polyethylene membrane is extruded into a series of studs which create a continuous air gap behind the waterproof membrane. On the face of the membrane a welded mesh allows plasters and renders to bond efficiently to achieve dry and durable finishes.

Delta-PT is watertight, resistant to high and low temperature extremes, chemically resistant to acids, alkalis, oil and solvents and is approved for use in drinking water applications.

With the bungaroosh being such an unreliable substrate, special cob fixings have been used for the installation of the Delta-PT. They enable the membrane to be fitted to mud walls, and are more than suitable for the bungaroosh.

The 8mm stud design of Delta-PT provides a continuous air gap which serves two purposes – to isolate the damp wall from the new plaster and decorative finishes and to allow ventilation of the wall for permanent dampness control.

The Slimline option of Delta-PT has a 4mm stud. The purpose of this is to allow only defective plaster to be removed, then Slimline Delta-PT to be installed. Replastering can then be carried out that will meet with the line of the untouched plaster.

The back wall of the property was particularly fragile, as it was subject to hydrostatic pressure, while the other walls only had rising damp to contend with.

On rear wall, drainage channel has been installed at the point where the wall and the floor meet. Any water that comes in will hit the channel and drain into the sub soil under the new damp proof membrane that has been placed under the new concrete slab floor.

As Matt Baker reflects: “Thankfully, the fact that one of our researchers had seen the Delta product range at an exhibition, gave us a point of contact to use.”

“Delta Membrane Systems were absolutely brilliant!” Matt states. “The company’s products and expertise helped enormously in this particularly challenging project.”

From Delta’s point of view it was a fresh challenge. As Delta’s Technical Manager, David Symes explains: “Not many people have come across bungaroosh as a construction technique, and the haphazard nature of this method means that no two walls are the same. However, we felt sure that our extensive product range in general – and Delta-PT in particular – would prove to be successful, and we were right.”

So, for one episode of ‘Help, My House is Falling Down’, Delta Membrane Systems is helping to ensure that this will not be the case.