Hi all,

Im looking for some advice regarding oversheeting of an asbestos roof.

During the recent strong winds one of our roofs was quite badly damaged. The roof was metal cladding sheeted over an asbestos cement corrugated roof. The strong winds have removed a substantial part of the metal roof. The asbestos roof was left undamaged during the storm - which was lucky given its age. The ACM sheets are still in good condition throughout. To paint a picture - the roof is approx. 4000 square metres.

Our insurers have given the green light to renew the metal roof and we have engaged a local roofing contractor to carry out the job. We have worked with the contractor many times in the past and their standards of safety are high. However, I'm looking for some advice on how they are proposing to attach the metal sheeting to the buildings roof structure.

They propose to anchor this with fixings drilled through the asbestos roof into the roof purlings at regular distances across the entire roof. Obviously, this raises concerns with me regarding the asbestos cement dust created during the drilling. To control this they propose to contain/collect the dusts by applying silcone sealant to the proposed hole location before drilling. I guess the idea is that this will dry containing the dusts.

Their employees do have asbestos awareness training.

I do have concerns about dusts falling through the hole - which is inevitable during drilling.

Having read the HSE Asbestos Essential A9 document, this describes a similar process. http://www.hse.gov.uk/pubns/guidance/a9.pdf

Just wondering, does anyone have any experience of similar activities?

The contractor would require non-licensed training in accordance with CAR Reg10.
I'm with Bob regarding improved control on the underside, which will require additional face-fit testing for those doing the clean up.
Although not strictly required, you might want to think about reassurance air and swab sampling at the end of the job to provide your employees with some comfort. Analytical companies who do these tests would also be best placed to advise you on appropriate safe methods and competency of contractors.

I am left pondering the circumstance whereby the existing metal roof has blown off but the asbestos cement roof is unaffected. What is the current metal cladding fixed to?

Hi, have just seen this thread if you read HSG210 it will tell you all the does and don'ts with regard to how to do the work, what ppe, type of equipment & training. What it does not tell you is that the hover (H type) will need to be emptied in a notifyed area that they need insurance to work with asbestos and the waste (from the hover) comes under the hazard's waste regulations & ADR
one other point is that swab testing is not a recommended test as you can get fibers in any invariament including buildings that do not have asbestos in them

Incidentally - for the record....Asbestos cement products are covered by ADR special provision 168 and as such ARE NOT regarded as dangerous for carriage.

Hi Gerry - thanks for your reply.

You say whoever does the work will need UKATA Cat B training - I'm struggling to find where this is stipulated in guidance or legislation - could you point me in the right direction? Or is this best practice?

I agree about the sealant - that was my thoughts entirely. The purlins cant be exposed and given the size and extent of the re-sheeting required we would need to remove AC running the entire length - effectively 50% of the roof - which is uneconomical.

Shadow vacuuming could be used externally or internally and this is something im keen to explore when the project team meets again on Friday. We are all going up for a closer look on a MEWP (harness to be worn and I hate heights!).

The operators would be wearing PPE and the building below would be empty so exposure limits would not be breached. The size/volume of the building allows for a substantial number of air changes per hour - again reducing likelihood of exposure limits being met.

The metal sheeting was fixed to wooden straps which were drilled and fixed onto the AC sheets. Quite a poor job really, although the insurers have surveyed the site and are happy with the previous method of fixings - which is rather strange to say the least! Some of the wooden straps were batons from pallets - quite shocking really.

L143, para 124 (b) specifies what is needed in this case. Yes, Category B training is UKATA terminology. Other training organisations are available.
No, the NNLW category has not yet been implemented. It is strongly expected that the revised CAR will be published in April.
I kind of thought that given the area of the roof that the removal of AC sheets might prove uneconomical.
You mention in your fourth paragraph about air changes etc. Don't confuse this with work in enclosures where air changes are a significant factor. The methods of working will determine the level of asbestos fibres in air and is the key factor to consider. And the main thing to consider is the 'control limit (0.1 f/ml)'. The size of the building and the air changes are not a key factor in my opinion. It is the intensity and duration of exposure generated at the point of work.