New timber deck, cleaning but black spots remain

[Ana08]

Hi,

I wonder if someone could help me. We built our new timber deck and waited 3 months (as I read that this would allow the tamins to come out). 2/3 of the deck is covered.
Yesterday, we had our builder who started the coating using spa n deck (many people seem quite happy with it). He started to clean the deck with Powerlift (recommended by Spa n deck) but not all the black spots came out! some wood lattices are particularly back. I posted some pictures.
Then he started sanding some of the black spots and had a first coat of spa n deck (natural). Next day he came and wanted to put a second coat and I stopped it. The deck was horrible with all the white spots from the sanding and still the black spots from the tamins. What he did today, was to test some of the areas and applied a stain to the sanded areas and then coated with spa and deck. Yes it does seem much better although not perfect. I am waiting to see how it looks when its dry and I guess that if we do 3 or 4 coatings, it will look good...but am not sure... will it?
The other worry is the black spots. Can we get rid of them without sanding? I read about Powerlift and it was supposed to get rid of it but it didn't... also I read that spa n deck prep should have been used and as far as I know it hasn't...would have that make a difference?
Thanks

[stevoh741]

My opinion is they will have to be sanded out. I would have hit it with oxalic acid (mixed around 25%) before coating that should have got them out. I am sure jimj will be along soon he is the expert on cleaning/sanding and using spa and deck. Do whatever he says to fix it.

[Ana08]

Thanks! hope jimj is around....There is only one coat of Spa n deck (applied when the deck was wet as recomended). So wonder if instead of sanding I could still use oxalic acid as you're suggesting.

[Trav]

Oxalic acid is basically deck cleaner solution. I had this problem a few years ago but I had oiled the deck first, then the black spot came. I used a relatively strong solution of Oxalic acid and a big stiff bristle broom (more like a scrubbing brush on a handle). After a few quality hours of scrubbing, most of the spots had gone. Not all, but most. Make sure you apply the liquid freely and let it soak for a few mins to help penetrate.

Hope it works for you too.

Trav

[stevoh741]

if the marks are below the surface coating then no amount of rubbing will get them off, the finish will need to be sanded. Oxalic acid basically bleaches the timber. You can buy it in crystal form from the shed for about $25. Most of the premixed deck cleaners have it at about 10% in their cleaning solutions - I mix mine to about 25% (about as strong as bare feet can handle it).

[Ana08]

Thanks for your responses. I understand that I have 2 options depending if the marks are below the surface. So will try a bleaching product and if not enough will have to sand some of the areas.
Now once this is done I will start coating. But how can I have a uniform coating? do I just coat several times the sanded/bleached areas and then the whole deck? do I first apply some colour product to these areas (and what would be the best)? I was using Spa n Deck natural but wonder if maybe a darker colour would be best. Again thanks very much for helping me.

[r3nov8or]

To be honest I think you are in for a world of pain trying to get colour matches if you bleach, sand, or a bit of both. I'd put it down to 'character' and enjoy a beer. But that's me.

[Blocker]

On new merbau it is critical you use the complete 3 part SpaNDeck system(no shortcuts).Powerlift must remain wet for around 10-15 minutes to be effective,followed by Woodprep solution then 3 top coats of colour.
IMO Walnut or Merbau topcoat is a nicer look than Natural on merbau timber.
If you shortcut the initial prep work the new merbau is not porous enough for finish coats to be absorbed effectively,and will shorten the life of the coatings.
Regards,
Blocker.

[Ana08]

Thank you Blocker. Yes, I do realize there was a shortcut so will review that. and will think about the merbau colour...and yes maybe at this stage I am stressing too much about matching colours and maybe best is to leave as it is.

[jimj]

Ana,

Sorry to hear about your troubles. You did what all the literature tells you. Let it weather for 3 months. You said a large portion is under a roofline. I am still puzzled as to how the various companies expect timber to weather when it is protected from the weather. I have no doubt the part out in the sun looked somewhat more faded than the part under the roofline.
Prior to coating the blacks stain should have been removed. The black stain can often be removed by oxalic acid 10-20% as it has a brightening-bleaching effect on the timber and is pretty good at removing the various black staining from timber. Most of the black staining occurs when some type of steel comes into wet uncoated timber.
Powerlift is really a liquid version of nappysan(sodium percarbonate ) 30% in strength. It will not remove the black stain. It is just a detergent that is good for dissolving dirt and oil. Merbau-kwila will yield tannin for ever. I have sanded 10 year old merbau-kwila and only put water on it and still have purple tannin come up to the surface.

Okay so as Blocker said the Flood instructions require
1. first step Powerlift ( soap)
2 second Wood Prep ( oxalic acid) focused especially on the black areas and worked on until they were all gone. IMOThis should have been done by your builder especiallyif he was being paid by you to complete the coatings as it is required by Flood. This information is easily obtained from Flood. They can even be contacted on Sat-Sun live on the phone for technical information. (p.s. )I don't work for them nor receive any kickbacks but have applied spa&deck to over 200 projects.
3. Application of Spa&Deck as all stains are developed to let us see things (grain,knots, different shades of timber etc) it can't work out what is good to see and what is bad. So the good parts look good and the bad parts not so good.

So how do we salvage this. I think as blocker suggested shift to a darker stain. I would look at walnut(darkest) or Jarrah. Jarrah is a little less orangy than the merbau tint. ( personal opinion). Will the black spots and sanding bits show through? Probably, but not as bad. Consider 4 coats in total instead of 3.

I come across this weathering a new deck and it becoming messed up frequently. Hence I always sand a newly laid weathered deck with a quick 80 grit sanding as this takes off all the grime,black spots, mill glaze(if still there) and instantly brightens the timber to the brightest it can get too. This gives me the best starting position for coating. However,in your case you have those wretched dome headed twist nails sitting above the timbers surface. Sorry as soon as i saw them I go into a mental rant. Your deck cannot be sanded with them sticking up. You can see where he sanded how much brighter the timber is once that top layer is removed.

I could go on about this weathering-nails-chemicals-tanins but as many who follow this forum have been subjected to my rants I feel they need a break on this one. If you dig through the archives you will find a many prior rants.

I wish you the best and hope you can have a happy outcome.

jimj restore-a-deck

[Ana08]

Thank you Jim and all that have responded. I also got in touch with Floods asking for some advice. I was very impressed with them. Actually their technical manager came today to my house and spent quite some time explaining the whole process, making some experiments etc...It turns out (as some have pointed out) that the 3 steps had not been followed. Basically the stage 2 - Prep spa n deck - was skipped. The black stains are indeed tannins. We poured a bit of prep spa in some of them and it worked, they're gone! not sure if the black spots will go on the areas that were coated several times but it's only a few... so all I have to do is go through each of the black spots/area and then re start the coating process. And will use a darker colour (Jarrah). Floods technical manager even offered to come again if my builder was going to finish the job...actually he declined and I will do it myself as I understood quite well what is needed. So again thanks and I am quite relieved that it worked out for me.

[jimj]

So glad that you have had some success. I have been using the Flood product now for the past 9 years. I have found they will bend over backwards to help you understand and sort out any issues,messups etc. I am not surprised that they came to your house,helped work out the problem and found a do able solution.
You can call their free number at 4pm on a saturday -sunday and talk live to their technical fellow Tom about any Flood product. They are the only mob to put a 2 year guarantee on their deck coatings against cracking,peeling or blistering. With over 200 decks restored I have never had a deck do this .
Disclaimer- I don't work for them just a happy Flood customer with both their products and their committment to the customer

jimj restore-a-deck

[r3nov8or]

Yeah, pleased you were able to solve this. Got a link to the details of this "3 Step" process? Doesn't jump out at me on their website.

[Blocker]

Go to Flood website,click on Brochure,scroll down to SpaNDeck,click on "download factsheet",covered under "Application".
Regards,
Blocker.

[r3nov8or]

Thanks Blocker. I guess it's all worth it in the end, but it does sound like a lot of prep, plus the costs of 3 products.