[Cob] Question about fungus treatment on timber frame

[dermitdemhut]

Hello people out there,

It's not a question about cob, but I hope that there is also people with experience in wood work in this mailing list, who might be willing to share some knowledge with me...

The problem: We are working on a roundwood timber frame structure and one of the rafters shows signs of fungus (grey and partly brown surface that smells like fungus when you rub it and put your nose close to it). The frame is made of oak that varies between 25 cm and 9 cm in diameter and was cut fresh in the forest and then brought to a shady place in the garden. After around 2 months the bark was removed. Some of the oak is now around 22 months and some around 9 months old, so it definitely got still some moisture in it. The rafters were cut in beginning of april this year and put in place beginning of september. The whole structure was then protected from the rain with a tarp that was build above it. The fungus started altough the tarp was above it. I got the inspriration and information for the building project from simon dale and his blog and I think he also used fresh cut oak so I thought it would work - especially when the structure is protected from rain and not touching the wet ground and with wind that can get through... But maybe I'm wrong.

What we tried so far:
1. I read that hydrogen peroxide kills fungus and that its not a dangerous chemical, so I sprayed it on the rafter, but 2 weeks later it looked the same. 
2. Today we removed the infected surface with a draw knife. Directly under the surface the wood looks healthy. But I think it will just reinfect again?

My ideas how we could go on:
I thought about treatening the fresh "pealed" rafter again with something that kills and/or prevents fungus (hydrogen peroxide again? Borax?). I also thought about the option of treatening it with terpentine and lineseed oil, but when it still has a lot of moisture inside, it's maybe not a good idea because it's maybe not the moisture from outside but from inside that causes the growth? I will bring a tool to measure the moisture in the wood within the next weeks.

Someone got an idea what to do with this problem? Or isn't it a problem at all because it's just a little bit on the surface and it won't rot through the whole wood as long as it's protected from the rain?

I would be happy about some thoughts on that.

Thank you,

Luchs
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