Stripping external beams

[dawntebbett]

We have recently bought a farmhouse 1615 in age, many of the beams are coated with a black tar like substance, particularly where there are imperfections in the oak.
This is causing damage to the timber below

We want to strip the beams, too big a job to be done by hand so we are thinking about shot/sand/soda blasting them
Can anyone recommend the best medium to use to strip the beams

many thanks

 

[Cubist]

Hello and welcome,
Others may differ but I would advise against any form of media blasting as it can be extremely damaging to both the timbers and other adjacent materials such as lime renders and plasters. Older timbers such as yours, which may have been painted lord knows when, will have accrued considerable moisture immediately behind the paint thus causing the wood to soften and lose its physical integrity to an unknown depth. Media blasting would remove all that material and could, in the worst cases, lead to some timbers needing to be replaced.

If you must do it then use the gentlest available material such as ice at low pressure AND a highly skilled operator who has referenced experience dealing with old timber frame houses. Even then, be ready to abandon the exercise as rapidly as possible.

Far better, in my view, to strip the old coating manually as in doing so you will incur considerably less damage to the timbers.

Sorry to be a damp squib, but good luck with your new home.

Cheers,
Cubist

 

[Toby Newell]

We have recently bought a farmhouse 1615 in age, many of the beams are coated with a black tar like substance, particularly where there are imperfections in the oak.
This is causing damage to the timber below

We want to strip the beams, too big a job to be done by hand so we are thinking about shot/sand/soda blasting them
Can anyone recommend the best medium to use to strip the beams

many thanks

I second everything Cubist said, PLUS advise against dry ice blasting, afaik the CO2 comes out at supersonic speeds.

I have seen two clients who asked dry ice guys to leave, one on my recommendation, because they were causing damage. I have many posts on this!

Dry ice was designed to be used on metal to remove bitumen / mastics / oleo resinous coatings (see my other recent post!)

Old wood can be more brittle and dry ice blasting can shatter it, I would not advise it, only good for strong, sound stone and metal maybe some sound new hardwood. There are engineering systems from Europe that vary the particle size and these can be very delicate, but these are for automotive restoration and the building bods are unlikely to have the delicate stuff.

So consider me an even damper squib.

And FYI, there may be rot due to moisture that cannot escape but your black stuff is likely to be asphaltum (see my other recent long post!) which is a form of coal tar and is an excellent wood preservative.

Best of luck and be wary the restoration industry is full of sharks, I know as my family have been swimming in it for seven generations.

If you manage to find someone good, hold onto them! The cheapest option is often not the cheapest!