External elm timber - protection/coating ?

[88v8]

One wing of my house, dating to perhaps the mid-1600s, has an elm frame with infill of brick/render and wattle/render. I fear some of the render is cement :shock:

The timber was all painted by PO with some hardware store matt black. This has been the case for the last 18 years, perhaps more. From a distance it looks good, but on closer inspection the paint has cracked in places, so damp can get in but is not able to escape.
Under the paint there might be filler, or pristine wood, hmmmm. There is no apparent external rot in the wallplate or elsewhere, but I have not done any prodding as I have plenty else to do, and in any case I would not want to make holes in the fabric at this time of year.

Last weekend however, I found some damp/softening/old woodworm in the elm wallplate inside the house. To an extent this may have been there for many many years, given that elm will withstand damp provided it stays damp. There appear to be multiple contributing reasons why it might now be getting worse, including the PO's paint. As part of the eventual rectification, I intend to have all the paint blasted off, leaving the panels bare for limewash, and the wood bare for.... ?

Normally, if this were for instance an oak window, I would reach for teak oil. Is there something better?

Ivor

 

[middi]

Traditionally elm would have been just lime washed. Later, during the Industrial revolution, the tar by- products of the era were plentifull and timbers were covered with the black stuff.

Unfortunately elm is sucseptible to woodworm a lot easier tha oak, albeit still a very useful substitute.

If the " paint" is cracking it is likely that modern paints may have been used above earlier tar based products.

I f you are not fussy about paint, and there is no conservation restriction you might as well use black sadolin after they have been cleaned. It will protect the wood and easily recoated.

Or you can cover them with limewash, that is a good insect repellant.

Middi

 

[robgil]

I didnt think they used elm that far back, I thought it was introduced in the mid 1700's as a building material. But then I guess they sometimes used what ever they had to hand.

 

[88v8]

The whole house is timbered in elm, although on the whole it's walled in stone. It's said to date from c1620.
Indoors, the worrum has indeed supped extensively. Upstairs a PO has had the (white) paint blasted off the beams, and the outer face, presumably soft and eaten, has been significantly eroded in some places.

I was thinking to coat the external timbers with something breathable. Is teak oil breathable?? Or should I be sealing it up, much as PO has done? Sadolin does not have much durability in my experience, and leaves the wood looking patchy where the sun has taken it off. Mind you, that's on iroko, which doesn't much like being coated with anything.

Ivor

 

[middi]

You are right Rob, elm was rarely used for the main frame of a timber building, nevertheless it was used.

It was very popular in the 18th C, especially for internal partitioning.

It is a rarity nowdays to find an elm mainframe building still standing, mainly because they were buildings of much lower status and if the poor costruction didn't make them collapse the woodworm usually did.

Middi

 

[88v8]

...if the poor construction didn't make them collapse the woodworm usually did.

:shock:

 

[Moo]

I intend to have all the paint blasted off,

and:

a PO has had the (white) paint blasted off the beams, and the outer face, presumably soft and eaten, has been significantly eroded in some places.

Don't jump to conclusions about woodworm. Significant erosion is an almost inevitable consequence of sand-blasting!

 

[robgil]

I dont think sand blasting can erode timber as much as wood worm can , in fact I'd say that the damage caused by both is entirely different, unless you are sand blasting it with an interest in destroying the timber instead of cleaning it.
Have you thought about leaving the timbers untreated? This is afterall how they would have started their career as a building material and seem to have lasted this long.
Obviously any badly damaged material will have to be cut away and new timber scarfed in to replace it.

 

[88v8]

I dont think sand blasting can erode timber as much as wood worm can , in fact I'd say that the damage caused by both is entirely different, unless you are sand blasting it with an interest in destroying the timber instead of cleaning it.

No, but clumsy blasting can erode timber which has previously been wormed. The worm typically eats the softer outer layers.
I understand it is in fact illegal to blast with sand nowadays, although I'm sure some still do as sand is cheaper than the legal alternatives.

As regards protecting the timber, I'd rather put something on it than nothing, so long as I don't seal it up. The wall in question is to the North and will get little sun to keep it dry.

Ivor

 

[Feltwell]

I understand it is in fact illegal to blast with sand nowadays, although I'm sure some still do as sand is cheaper than the legal alternatives.

You may be right, but I think using crystalline silica for blasting was banned way back in the 1950's - so there's not likely to be much old stock of blasting sand laying around, unless people are just using any old sand. Silicosis is not a pleasant way to die.