I've got some fairly new cedar cladding, it's British western red cedar. Installed during the Autumn. It was all stored well for a good period of time, in a well ventilated, cool dry place out of direct sunshine. It's had a very wet winter and I've noticed some spots on the north face where there are dark spots starting to appear across the surface.

Interestingly, for now it's only appearing on the parts of the cladding that get wet when it rains, so two bay areas and facias - the rest of the house has a generous overhang.

The cladding is untreated.

Clearly this stuff is feasting on the sugars in the wood and darkening it as it goes. After about 3 years I guess, the food will be gone and we won't have to worry to much about it. However, my concern it that this might potentially darken the cladding beyond the silver we were hoping for.

And obviously now that I've seen it, it seems to be growing exponentially by the day -I'm almost sure one plank has gone black overnight!

My questions are:
1. should I concern myself with this initial part of the ageing process at all? just let it happen?
2. should I consider putting on a penetrating mould and fungal treatment right now before it's too late?

If 2, what should I use:

Would a simple Borax based solution, sprayed onto the surface suffice? Any other anti-fungal/mould solutions that still leave a clear finish?

Alternatively, I've come across SiOO:X wood protector, a silicate based solution, but it costs a fortune. I've also come across Sansin SDF which seems to cost even more.

What would your approach be and why?

Alternatively, I've come across SiOO:X wood protector, a silicate based solution, but it costs a fortune. I've also come across Sansin SDF which seems to cost even more.

We used SiOO:X on our cedar cladding. We coated the wood before it was installed, a year last August (19 months ago). It has behaved as expected and is now an even light silver colour all over. Yes expensive and took an age to coat all the planks, but it looks great. A neighbour in our village has similar cladding installed at the same time. I have to say ours looks a lot better!

Posted By: dicksterSimonD,

I posted a sweet chestnut version last year.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16548&page=1#Item_0" rel="nofollow" >http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16548&page=1#Item_0

Just used rainwater and a stiff brush. I have to say that it has darkened somewhat over the winter and a Forth Bridge situation might be on the cards (if I can be bothered).

That's an amazing transformation you achieved there, nice one!

Posted By: revorSee what Owatrol can do for you.https://www.owatroldirect.co.uk/" rel="nofollow" >https://www.owatroldirect.co.uk/They do a v good range of treatments for wood and other substrates I used their products on my cedar cladding. I used Seasonite as preservative/ primer with a SCS as finish coat. . This guaranteed for 5 years on horizontal surface and 15 on vertical. I am sure they will have an answer to your issue. Also Promain

https://www.promain.co.uk/manufacturers/owatrol.html?" rel="nofollow" >https://www.promain.co.uk/manufacturers/owatrol.html?
gclid=EAIaIQobChMI_aqxj4bb7wIVzt_tCh2SaghiEAAYAiAAEgLl5_D_BwE

They are very knowledgeable sell Owatrol and other makes. I think they know more than anyone about coatings.

That's great. I haven't come across Owatrol and will check it out. I know Promain well as I've used them for steel coatings and paints but hadn't considered them for timber. Cheers.

I charred the last cedar boarding I installed (see Shou-Sugi-Ban) - before installation, of course.

It's supposed to make it more resistant to rain, mould & insects by burning off those sugars. Working OK so far, but only a few years old. At least any mould will be less noticeable...