Case Study: How one couple flood-proofed their property
Architects Diarmaid Brophy and Sterrin O'Shea worked with engineer John Pigott of CORA to specify the waterproofing works at Mike Roche and Paula Russell's home in Harold's Cross, Dublin - a two-storey over basement house dating from the late 18th/early 19th Century.
According to Brophy: "It's important to get specialist independent advice for items such as waterproofing and flood protection to ensure you are selecting the right solutions for the building.
"On this particular project, we were fortunate to have CORA engineers on the job as they have much experience in the area of waterproofing and flood protection."
Obviously each property will have its own individual requirements, but in this instance these were the works carried out, along with a summary of the costs involved.
1 A "non-return" valve was fitted in the front garden on the drainage pipe connecting into the public system. It closes if water starts flowing back up the public drain. "It has kicked in a few times," says Roche, "so we know that it's doing its job." Cost €2,000
2 A 2,500-litre water retention tank was buried beneath the patio in the back garden to store waste and rainwater while the non-return valve is closed. Cost €4,000
3 Waterproofing membranes were applied under the new floor and to the inside of the existing walls at basement level. A new concrete floor was installed in the basement and the waterproof membrane was placed underneath it. Two different systems were used. One was the "cavity drain membrane", which has a "dimpled" type structure. If water gets through the wall, the water runs down to ground in the cavity formed between the cavity drain membrane and the wall, keeping the interior dry at all times. Some of these cavity drain membranes can be plastered directly onto. This was used on the walls in the lobby area under the steps leading to the front door, and also under the new concrete floor.
The other system was a waterproofing coating that was applied to the inside of the walls. When dry this system forms a flexible, impermeable membrane that prevents any water coming through the wall to the inside. The different treatments were carefully sealed at the junctions to form a watertight envelope.
There are a number of different systems available depending on whether you allow for water to come through the wall - using a cavity drain system to give it somewhere to go - or use an impermeable system to stop the water coming through at all. Cost €9,000
4 A flood gate barrier was bought for the entrance door to the basement which can be installed manually if required to prevent water coming in. These are available online. Cost €600
Total cost of flood protection measures was €15,600, and this work was undertaken as part of the overall refurbishment work.