blackbutt deck

[the juice]

hey hey hey
just laid a deck in 90mm blackbutt in the hunter valley left it exposed and untreated came back 5/6 weeks later to treat it but--:eek- it is now cover in thin spotty black mould/stain like thing haven't got a clue as to what it is. The deck now looks about eighty years old.
It sands out eventally but will it return and am i best treating it with a stain, oil or varnish . any help or advice most appreciated

[Scally]

Untreated timber left to the elements is likely to grow mould.

It doesn't look too good on a deck but we use blackbutt for timber boardwalks on beaches because of its durability. The heat killed the mould. If we had a lot of wet weather the mould would grow. The untreated timber turns a silvery grey out in the elements. We expected it to last about 40 years, untreated and out in the elements.

The Hunter is a warm place and there is a reasonable humidity. Good conditions for mould to grow.

Any finish will keep the moisture out. No moisture - no mould.

Staining won't make any difference.

Clean up the deck by sanding or a commercial mould remover. You need to get rid of as much of the mould as possible so I would suggest a mould remover.

Let it dry if you use a mould remover.

Apply your finish and the deck will look a million dollars for years.
Give another coat when it looks like it needs it.
The pics are of blackbutt flooring, also in the Hunter Valley.
It comes up pretty good.

It has an Intergrain finish. They have an outdoor version. Feast and Watson have a good outdoor finish that I like because it contains tung oil. The finish can be almost flat to gloss. There are good oil finishes available too.

Clean it up, put on your finish and will enjoy it for years.

[Exador]

It has an Intergrain finish. They have an outdoor version. Feast and Watson have a good outdoor finish that I like because it contains tung oil.

Just a note on finish brands. According to the rep from Orica, Intergrain is their premium brand for this sort of thing, while F & W is the budget version. A good example is Intergrain Dimension 4, which is a timber pre-treatment containing acrylic, wax, anti-fungals and UV stabilisers. There is a F & W product (forget the name) which is the same product but with more acrylic, less UV stabiliser and no anti-fungal. None of that is on either pack. Caveat emptor.