The rising walls were built within a week and then radon barrier is put on. This one of the jobs that the self builder can do himself. It is best done with two people and on a day with low wind. Although it is a relatively simple job it requires time and patience. It is a high gauge plastic sheet (red in colour)and sealed with double sided butyl tape at all the joints. Special top hats are required for pipework coming thru floor. We put down radon barrier for 2 reasons, one being the prevention of ingress of moisture from the ground below and two, the prevention of radon gas omitted from the ground emanating into the built dwelling. Radon gas is more prevalent in certain areas than others but even so, it is a legal requirement to install it regardless. If you live in an old house and want to check if there is radon present you can get a test done for approx. €50 from the Radiological Institute. The presence of high levels of radon gas in a home can be a contributing factor to cancer.