Lets start with a bit of history.
Asbestos is a natural mineral that is extracted from expansive mines, and is still being mined today, mainly in China & Russia. They are commonly known by colours, blue, brown and white. The former being the most and the latter being the least carciogenic. Asbestos has many great properties such as heat & chemical resistance, sound absorbsion, tensile stregnth and electrical damage. This is why it was so widely used in so many industries. Asbestos can be found in ceiling tiles, insulating pipe lagging, string, brake pads, window sill tiles, roof sheets and fire prrofing materials and many other products.
It is now known that handling asbestos can be dangerous and prolonged exposure to asbestos dust can cause deadly illnesses such as lung cancer, mesothelioma and asbestosis, so adequate personal protective equipment (ppe) is necessary . The potential health effect were becoming known as early as the 1920, but it wasn't till the 1980's and 1990's that asbestos use had started being banned out right or heavily restricted. Building owners where asbestos is present have a duty to manage any asbestos containing materials by making everyone aware of its presents and ensuring it doesn't deteriorate. To carry out disruptive work to asbestos in the UK, contractors must have a licence otherwse you risk prosecution, but there are a few services which does not require a licence (but are still regulated) such as; asbestos fibre cement roof cleaning and coating.
Asbestos containing materials must be diposed of in the correct manner by adhearing to strict regulations. In the UK and many other countries, asbestos waste must be double bagged in 500 guage clear sacks and transported to landfill in asbestos marked skips and vehicles. Some asbestos products can be recycled by superheating to 1000-1200 degrees celcius to produce silicate glass which can be made into stone tiles and ceramic bricks
Asbestos roof cleaning process
If you have an asbestos roof and there are a few holes and cracks causing water to ingress, in most cases it is possible to clean & coat the asbestos, rather than costly replacements. Replacement generally costs 50% more than roof repair.
This should only be undertaken by persons who are experienced in working with asbestos, but at the very least must know the regulations and have taken an asbestos awareness training course.
Firstly, double guard rail fall edge scaffold must be erected around the roof egde and crawler boards used when on the roof to prevent falls from height. An asbestos roof must always be presumed to be unsafe to walk on and the locations of roof lights must be known. If possible, install netting on the underside, in case the worst did happen.
Now we have the safety measures in place, we can start to clear the roof of moss
Brushing off the large clumps of moss before cleaning will make the pressure washing stage much easier and will ensure the filtration system is not overwhelmed with big lumps! The moss is also much lighter when dry, so brushing it off will also make waste disposal cheaper.
Cutting off the excess bolts will ensure the rotary cleaner glides down the roof without getting caught and possibly casuing damage to the rotary head in the process! Making the butyl process quicker and more effective is another good reason to cut down the bolts (we will get to that bit later).
We would the set up the water recovery system and divert it to large tanks for filtering. We begin pressure washing by allowing the rotary cleaner to roll down the roof and pull it back up once it has reached the bottom. This will normally require two people. While that is happening, somone id filtering the water to 5 microns, we use filter socks and a large pump which pushes the dirt through under pressure. This is a painstaking process as the filters are contantly clogging! Once the cleaning is complete we would go over the roof with a turbo lance to ensure the edges and ridges, which the rotary cleaner may have missed, is cleaned. The roof will then require a wash off to remove dust and spray from the washing process.
Asbestos roof repair & coating preperation
As you can see, the roof is now completely clean and ready for repair. Lets get started with somthing simple. For the purpose of this article we are using Isonit IsoRubber roof coating system. This system comes with a 10 year manufacturers warranty against leaks.
We set up the airless sprayer and cover the entire roof with a product called; Construction Primer. This soaks deep into the asbestos or fibre cement, binding with the fibres which stregnths the sheets and provides a solid bond for the repair tapes and top coat. Once dry all bolt heads are covered with a thick peice of butyl tape (butyl is hydrophobic and will repel water, preventing ingress). We peel off all flaking peices of asbestos, bag up and dispose in the skip. All cracks and small holes are covered using fleece back butyl tape. If specified in our initial survey, we spray apply Vision shatter proof clear sealer to the rooflights to prevent further UV degradation.
Now all the repairs have been carried out, the roof should be watertight. The top coat is spray applied to waterproof the pouros asbestos sheets and protect the repair tapes from uv light as butyl is not a uv stable product.