Timtan 6th October 2009, 09:53 AM Hi all,
I have a new deck/pergola built over the last fortnight before the rain came in over the weekend. The deck is tallowood with treated pine stumps and pergola with laserlight covering, and the builder gave it one coat of oil all round before putting it in. Before you know it the black marks/spots appear within a day or two of rain.
Seems to be worst where it was most exposed. Any idea what this may be - mould, sap etc etc ?? And does anyone have any suggestion on how to fix it?
Photos attached of the worst section plus an "emerging" section.
Thanks.
DJ’s Timber 6th October 2009, 11:32 AM G'day Timtan,
Cannot help you on your problem, but I would suggest that you go over to our sister site RENOVATE FORUM (http://www.renovateforum.com/index.php), join up and ask the question in FLOORING, DECKING, STUMPS, etc. (http://www.renovateforum.com/f77/)
EMistral 6th October 2009, 12:05 PM 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.
kman-oz 6th October 2009, 12:45 PM 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.
AlexS 6th October 2009, 05:58 PM 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.
Timtan 8th October 2009, 11:03 PM 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.
Harry72 10th October 2009, 06:48 PM 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.
Huz575 21st September 2023, 10:50 PM 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
Old Croc 22nd September 2023, 08:11 AM Huz, he hasn't been back on the forum since then, so you won't get a response from him.
Rgds,
Crocy.
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