Thread: Help!! What is that on my new deck?

G'day Timtan,

Cannot help you on your problem, but I would suggest that you go over to our sister site RENOVATE FORUM, join up and ask the question in FLOORING, DECKING, STUMPS, etc.

Hi timtan,

I built my privcy screen out of merbau last year and after many researches, especially on protecting the work, I found that prior to applying the finish, it had to be "soaked" to release the tanins.
That's what I did plus a couple of days of raining and I ended up with some stains similar to yours but they washed away with a high pressure cleaner (not too high pressure so that it did not damaged the timber).
I repeated the operation twice I think until there was no more stain coming out of the timber.
Then I applied the oil.

Was there any steel work done on the pergola? Iron/steel filings from grinding will react with the tanons in the timber when they get wet causing black marks. The patterns on the deck suggect there was some grinding/cutting donw near by.

From the colour & pattern, I'd bet that K-man has got it in one. If you can sand it and collect the sandings, then re-oil, you should be OK.

Thanks all. I'll try to scrub down with the formula noted in the renovate forum (napisan) and see how it goes, don't like the idea of having to sand it... but see how we go first. Will keep you posted.

Yep definite on the tannin, napisan will bleach it.
Tallow will always stain if it gets wet, its one of the worst woods for it.

Hey there I know this post is very old so how did u resolve the issue ?? I think I have the same problem with a 2 week old Tallowwood deck… Thanks

Huz, he hasn't been back on the forum since then, so you won't get a response from him.
Rgds,
Crocy.