Replies

1. 
   MarkH | Feb 25, 2006 02:23pm | #1

   I don't know, but that sounds like a potentially bad idea.  If asbestos fibers were released by the washing, they could dry out and be dispersed into the air. 

   I think it is highly likely that the asbestos is bonded in the cement, and would be no problem.  Not sure though.

1. 
   DaveRicheson | Feb 25, 2006 02:56pm | #2

   I have never seen asbestos cement siding shingles produce friable fibers unless they are broken.

   It has been a loooong time since I have done any siding over work that involved asbestos/cement shingles. Can they produce  friable fiber from wet abrasion?

   During normal asbestos abatement water is used to control asbestos dust, then a wet vac is used to remove any water containing fibers. All waste is then double bagged and goes to the landfill with tracking documentation.

   IMO if he power washes the siding, any fibers he produces will be washed into the ground. That in itself may be a problem, but I honestly don't know.

   I would check with the state or local OSHA authorities to be sure before I started a project like this. It is better to know the rules up front than face a fine or lawsuit from taking a WAG.

    

   Dave

2. 
   rjw | Feb 25, 2006 04:02pm | #3

   I'd mainly be concerned about the skills of the person doing the work - those shingles are fairly fragile and easily broken if the stream id too concentrated and powerful.

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1. 
   PearceServices | Feb 25, 2006 04:25pm | #4

   Joe,

   It comes down to science, there is a bond strength to any material, as you increase water pressure, you increase the capacity to overcome this bond strength. they have actual formulas for this.

   For instance, sound concrete can be cut with a water pressure that exceeds 3.5 times the compressive strength of the concrete. 3,000psi concrete will cut at 10,500psi of water pressure. The way to remove only unsound/spalling concrete is to set your pressure to 9500 or 10,000, it removes whatever is unsound, leaving sound concrete.

   Your asbestos (cement based)siding will respond the same way to a particular pressure.

   The point is that even new siding can be cut with water pressure, and old siding like yours, with 30-40 years of the elements will have some deterioration. It's a guessing game  as to what pressure will remove deteriorated materials, I'd guess that its not too high of a pressure. Your typical pressure washer would most likely not remove sound materials.

   Since asbestos is not a thing you just guess at, I think you need to have a sample taken, pressure wash the worst, most exposed area, collect all the water, and send it to a lab for testing.

   Let us know how you make out

   Edited 2/25/2006 8:25 am ET by PearceServices