Mouldy internal beams

[Antony Keeble]

Hi all, we have a oak framed building from 1604 and the ground floor internal upright beams that joins the oak sole plate are showing signs of mould, externally there some kind of mastic that is crumbling away allowing water to sit on the sole plate and allowing a capillary action n to occur causing the mould, how
do I seal that point where the vertical beam abuts the sole plate

 

[TudorCottage]

I would start by getting all the mastic out. This will probably bring some wet crumbly wood with it. Depending on how much wood you lose before you get to solid wood, would determine my next move. If it’s not much wider than the mastic I would fill with either burnt sand mastic or a lime based filler. I’ve used both with good success. I would smooth it off at an angle that lets rain water run off it rather than sit on it. If water does penetrate they are both breathable products so after a spell of sun and wind it should all dry out nicely.

If the wood decay is more serious but not enough to cause any structural issues I would think about replacing with new oak. That’s not as daunting as it may sound. I’ve done it on quite a few areas of our timber frame and have been pleasantly surprised with the results. Admittedly I’ve always reached solid wood very quickly.
I use a multi tool and the first few times are quite daunting as you drill away wood that might have been there 500 years, but in reality it’s not much more than powder, you’ll soon know when you reach solid oak. I then make the surface as flat as possible and cut a piece of oak to fit and peg it to the existing oak with dowels. Aesthetically pleasing more than anything else but it must make that area more water resistant.

I revisit these areas frequently to keep an eye on them and a couple of years later they seem nice and solid and dry and the surrounding areas of wood seem to be in better shape as well.