Since the cement sheets were fireproof manufacturers initially considered them safer as compared to wood.
Overlaying asbestos cement roofs.
We consider asbestos cement roof shingles a durable and fire resistant roof and an asset to the building provided that the roof is in good condition.
But because asbestos cement roofing is easily damaged by a heavy footed worker unfamiliar with the materials involved asbestos cement roofs have to be repaired and maintained with the same care.
Further the cement sheet contains asbestos fibres and cement.
The use of asbestos cement roof shingles was growing at a steady rate in the united states.
The overcladding of an asbestos roof is a cost effective roof refurbishment process that minimises the disruption at site.
In the early 1920s american roofing material manufacturers johns mansville carey eternit and century were all offering at least one asbestos cement roofing shingle to their customers.
Corrugated roofing sheets made of asbestos is common in uk homes constructed prior to 2000.
Typical life of cement asbestos roofing.
The cement sheet is a building material made from asbestos fibres.
Many of these built in the 1950 s and 60 s and are now beginning to leak.
The overcladding process also reduces the costly disposal of the existing asbestos roof sheeting that must be sent to licensed landfill.
One idea is to overlay the roof with insulation and steel sheets.
Historians from the portland cement association report that the use of asbestos fibers in concrete mixes reached its peak in the early 1900s.
Typical roof wear or failure patterns are either failure of the shingle fasteners or broken and falling shingles.
However many asbestos roofs are built with concrete portals meaning the roof is supported by a small number of concrete arches.
The benefits of asbestos overcladding.
Roof cladding requires bolts to be drilled into the asbestos roof.
At that time the minerals were the most common added ingredients in a group of construction materials known as fiber cement composites.
The list of products made from these composites included.
First you must fit the spacer bars.
Adding asbestos to the cement made the corrugated roofing sheets more heat resistant weatherproof and durable.
The insulation is then installed into the framework often an ashgrid system so named after the original manufacturer ash lacy construction and the metal weather sheet is the fixed to a bar.
The first stage is to fix a framework to hold the metal sheets in place directly to the purlins underneath the asbestos cement roof sheets.
This means the new roof cannot get enough stability on top of the old one a common risk of over cladding.
Then if you wish you can add insulation.
It is mainly important as a roofing material.
When overcladding an asbestos cement roof it will also be necessary in most cases to include a layer of insulation to meet current day building regulations.
