We are currently having a bit of a mould problem on some of our white pine timbers. What is the best way to prevent this and what can be done to the timbers that already have the mould and were just about ready to ship to site? We are using a natural oil finish just prior to shipping.

Our sawyer dips the pine timbers in some solution before he ships them to us in the summer months. I'm not sure what the chemical is, but it stops the mould growth for about 6 weeks. It's only a surface treatment, so as soon as the timber is sanded, it is gone.

If the mould starts up, we spray the timbers with 3 parts water, one part bleach. This kills the spores. In really humid weather we have to go through the frame a few times and spray it, then again at the site. We don't oil the timbers, so I'm not sure if it would affect the finish.

The fungi that causes blue mold, which in its initial stage doesn't effect the strength of the wood, can be controled in a number of ways. Temperature is one control. Growth stops below 40*F and above 105*F. Oxygen deficiency stops it and moisture content below 20 % or above the saturation point also stop it. Sapwood is what the fungi thrives on because of the carbohydrates stored in the cells. So its not so easy to stop, unless you want to be raising your frame in the the winter or under water, the best way to control it is by using dry timbers, or chemically inhibiting the fungi. Borate salts (Borax) kills the fungi. There are commercial solutions that can be sprayed on such as YardGuard, Timbor etc. These can be obtained from log home supply places like Canadian Log Home Supply (1-800-746-7773)or contact a local sawmill and ask what they use to dip their lumber in to prevent staining. Hope this helps.

Forgot to addrerss the removal.You can try anoxalic acid in solution to remove the blue stain. If it is real bad though try a two part system such as from American Building Restoration. It contains concentrated liquid solutions of sodium hydroxide and hydrogen peroxide. You can get boiled linseed oil at most hardware stores with a fungicide in it also to prevent mould in the finish.

For information on wood protection and durability please review Forintek/CWC website www.durable-wood.com
Forintek also recently completed a publication on protecting and finishing log buildings. Lot of your questions regarding protection and cleaning of wood are addressed there. The document can be viewed at http://www.forintek.ca/public/pdf/fact%20sheets/LogHome15sept03.pdf

Regards

Dalibor

I'm bringing up an older post.

I have similar issues with my white pine frame. I just couldn't get my roof on quick enough. Rain water got into the bottom of the posts and turned them black. It was beautiful weather during the raising and unfortunately I did not remember to put Anchor Seal on the fresh end cuts at the bottom of the posts.

Will the methods/solutions mentioned in this post also clean up the bottoms of my timbers. Also, if a bleach solution is used will it leave a strong smell in the pine timbers or does it dissipate after awhile?

Don't know about pine, but 1 part (chlorox) bleach to 1 part water does wonders to the timbers in our frame (14 kinds of hardwood). The frame has been up for almost a year and now we are closing the last bit of it in. Right now we're just cleaning the side of the timbers facing the SIPs, since we won't be able to reach that side when the SIPs are all on. No, there is no smell afterwards. We rinse with water, but there is still a chalky hue to the timbers when they dry. I think another rinse + oil will bring the color right back. (the color comes right back whenever we wet the timbers). FWIW, Boracare (similar to Timbor, but supposedly better) did not prevent my timbers from mildewing.

-Thomas