Brand new Garapa deck: water stains after rain

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morbandit

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#243470 12-Dec-2018 23:53

Hi all

In the process of installing a new Garapa deck. Have oiled all sides of all the planks (and left to dry in the garage for several days) before install. Also sealed the cut edges with a wax end sealer.

It rained last night and today I noticed several water stains on the partially finished deck that didn't come off with a sponge or mop. Any thoughts on why this might have occurred? A couple are so bad I've had to sand them off...

I used Dryden Clear WoodOil.

Bandit

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#2144660 13-Dec-2018 09:43

It sounds like you oiled them before install? Was the timber seasoned before you oiled it?

mdf

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#2144661 13-Dec-2018 09:48

Pictures would be helpful, but I'm guessing tannin leaching if it's new wood that hasn't been exposed to your weather conditions previously.

Bung

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#2144695 13-Dec-2018 10:39

Garapa supposedly has negligible tannin release. At least 1 supplier makes it a condition that it must be oiled before installation.

When it rained did the water bead uniformly on the timber? Maybe the take up of oil wasn't even allowing water to penetrate.

morbandit

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#2145097 13-Dec-2018 21:35

Will take some photos tomorrow

Bandit

Paul1977

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#2145259 14-Dec-2018 11:03

Bung: Garapa supposedly has negligible tannin release. At least 1 supplier makes it a condition that it must be oiled before installation.

When it rained did the water bead uniformly on the timber? Maybe the take up of oil wasn't even allowing water to penetrate.

I'm curious, why oil before installation? What is the advantage of that?

EDIT: OK, recommended to oil all four sides - I guess that would be difficult to do after the deck has been laid!

Paul1977

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#2145264 14-Dec-2018 11:22

I don't mean to hijack the thread, but this whole "oiling before installation" piqued my interest.

I just did a quick Google, and some places are recommended the same for Kwila - oils all 4 sides prior to installation. This is completely the opposite of what I was told when we put in our Kwila deck. Because Kwila has a lot of tannin I was advised to install the deck and then hose it down frequently over several weeks (and hope for a decent amount of rain) in order to leech out the tannin before oiling it.

Paul1977

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#2145270 14-Dec-2018 11:52

@Morbandit Could it be not enough oil?

Did you oil the boards while they were laid flat or were the standing up? One coat or two?

Generally the first coat of a deck (a laid deck anyway) is a "flood coat" as bare timber can soak up a lot of oil so you apply a good amount. However a lot of this would run off instead of soak in if it is standing vertically.

EDIT: Also, the timber wants to be thoroughly dry before applying oil.

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morbandit

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#2145407 14-Dec-2018 16:14

Yes oiled on all 4 sides. It was completely dry before I oiled. I stored it fillet stacked (flat and separated by a piece of wood to allow airflow). Oiled about a week before installation.

Was always my intention to apply a second coat once installed - but unfortunately we had rain half way through and lo and behold got these water stains.

As I say I sanded off the worst of them (which also included black stains, from googling due to iron particles).

See photos here:

To be clear these marks were absolutely not there until after it rained. Let me know thoughts! I'm hoping a second coat of oil will resolve the issue...

Bandit

mdf

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#2145499 14-Dec-2018 18:39

Looks to me like the bleed can be traced back to a screw hole. I suspect the water is getting in there and causing discolouration (maybe tannin leaching, maybe just wet) under the oil. If it dries out, oiling the screw holes might sort it out (that's a guess though) but you don't want to seal it with it still wet inside; it will just bubble the oil off.

morbandit

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#2145554 14-Dec-2018 21:19

Nice insight, thanks. I've done a second coat of oil on half the boards, and will do the rest tomorrow, so next time we get rain will be interesting to see if the second coat is enough to prevent the staining.

Bandit

Paul1977

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#2147652 19-Dec-2018 10:31

mdf:

Looks to me like the bleed can be traced back to a screw hole. I suspect the water is getting in there and causing discolouration (maybe tannin leaching, maybe just wet) under the oil. If it dries out, oiling the screw holes might sort it out (that's a guess though) but you don't want to seal it with it still wet inside; it will just bubble the oil off.

There are definitely distinct patches that aren't near the screw holes at all though, and would the moisture really migrate that far in a hardwood like Garapa?

@morbandit how has it come up after the second coat?

morbandit

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#2148122 19-Dec-2018 22:41

Second coat *seems* to have made a big difference. It just started raining again today after quite a long dry period so will be interesting to see how it goes over the next few days.

Bandit

morbandit

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#2148220 20-Dec-2018 10:01

Spoke too soon :( absolutely terrible water damage. This is after 1 coat on all sides pre-install, and 1 coat on the top after install. The second coat took around 48 hours to fully dry.

Any ideas? Feeling a bit distressed given how much this garapa has cost me.

Bandit

mdf

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#2148233 20-Dec-2018 10:17

Mate, that *suuucks*.

In the first photo, there seems to be no staining on one board and heaps on its neighbour. Any difference between those two? Installed at different times, one coat vs two etc.?

morbandit

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#2148242 20-Dec-2018 10:26

A few of the boards have had 3 coats due to the order I did it in, but no noticeable pattern. Some of the boards seem to be more "thirsty" than others, but couldn't say for sure it was these boards that are staining worse. Doesn't seem to be any rhyme or reason.

Maybe I need to admit defeat and contact a decking expert?

Bandit

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