Cement Stains on old beams

[benmc]

Hi All

I have a problem with concrete stains and residue on old beams.

The previous owners and people who converted our Church boxed in a large number of the original exposed roof trusses and beams. As part of this work they built block-work to the underside of the beams and then mortared the remaining gap.

We are in the process of uncovering the beams and have found large amounts of cement/mortar on the beams. It is generally very thin ie feels like the trowel have been wiped across the front of the beam. See bottom right of attached photo.

So how do I remove this residue? I dont want to sand as the rest of the beams are in original stained condition. Any advice?

Ben

 

[Penners]

I'm no expert but I think you're going to find this a bit difficult. The normal products used to remove cement stains all rely on acids (cement being alkaline) - some of them extremely strong. I don't know what effect these would have on the finish that you say is on the wood beam, but I suspect it would fairly deleterious.

Have you tried just giving it a good scrub with a scrubbing brush and detergenty water? If that doesn't work, I suppose you could try a small test area with some gentle acid like vinegar, but I doubt that it'll be strong enough.

I suspect that you may end up having to sand it off and refinish.

 

[Toby Newell]

Hi

The beams do not look like they are in their original stained condition. They would have been linseed oiled or shellaced and waxed. The only way you remove the mortar is to strip them, see

http://www.periodproperty.co.uk/ppuk_discovering_article_023.shtml

for some tips. The stain looks like a modern pigmented finish, I would strip off, shellac and wax them, they will look a thousand times better

Toby