Elaine Toogood of the Concrete Centre recently wrote an interesting Blog http://www.thisisconcrete.co.uk/home_page/blogs/painted_concrete_-_elaine.aspx about painting exposed concrete, particularly soffits. This got me thinking as on many projects we work on the stock solution for fixing any problems (contractor banter) is “paint it”. I can see the attraction from a trouble shooting perspective but thus far have never experienced it myself.
We’ve been consulting and training local contractors on cleaning a soffit recently. The surface area is huge. Basically the soffit is top notch but is as troublesome as the last one I saw. Whilst cast extremely well it has a multitude of stains from reinforcement rust, airborne dirt, boot dirt, the odd poker burn, and the ever present dogbone spacer indentation. The staining is really the issue here and how to get it off. Covering it with paint would be a solution of course but I suspect this will not be the route in this instance and would (in my opinion) destroy what will be a very beautiful piece of architecture.
Cleaning soffits can sometimes be done dry but also may need to be done wet. If the soffit is struck and has a mildly dusty surface (perhaps MDO formed) then often stains can be removed using a dry mechanical method. This is a real bonus as it cuts down on a lot of time and effort. If the surface is very dense we have found that usually the stains are harder to budge and need to be removed or reduced using a wet mechanical method.
Each section of soffit needs to be thoroughly wetted down (spray but no jet wash), scrubbed with a flat head mop, abraded by a flexible diamond coated pad, squeegeed off (perpendicular to the wood grain on the board), buffed to remove any dirty slurry, left to dry then seal if appropriate. To clean a standard board takes between 10 and 15 minutes. It’s quite an undertaking, back breaking work and needs to be done with the utmost of consistency. The result is worth it though as the surface remains intact as the abrasive action is gentle enough to not remove the surface mortar. This leaves the soffit ‘as struck’ so to speak. Great care needs to be taken in not introducing a shine to the surface.
Soffits will always be difficult because their surface area is subject to getting a bashing from the elements and human traffic. Unlike a wall or column for example, the formwork surface is extremely hard to protect when considering the nature of building sites and the normally huge surface area you’d be dealing with.
Perhaps there is merit in specifying a painted finish from the outset on soffits. There is most definitely merit in undertaking the aforementioned cleaning regime. There is also huge merit in understanding that soffits are probably going to be pesky in the first place. So expect to have some intervention when struck and realistically budget for it.
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