Sanding before oiling?

[aragorn234]

Have completed deck building and have punched all nails.
Do I really need to sand the deck. The boards (Merbau) are starting to go a little grey so I am guessing I am really in need of getting the oil down.

I am hoping that the oiling will rejuvenate the color and look of the deck?

I am thinking that if I dont sand it back what are the draw backs of this course?

If it looks crappy after oiling with no sanding can I still sand it back and reapply oil?

The reason I am not just going for the full sand and then oil is time (baby on the way) and have many other projects that need doing before baby due.
Also I am concerned about the sanding not making the board color even.

Please supply me some advise I am really torn on which way to go. I want to get it done this weekend (17 - 18 Feb 07)

Thanks in advance

[Gumby]

sandin g will lighten the finished colour a lot but it will darken again pretty quickly.

If it's smooth, don't bother sanding. Just get the oil onto it.

Mine wasn't sanded and looks ripper-grouse

[aragorn234]

If I do oil it and dont like the finish can I sand it and re oil it then?

[strangerep]

Have completed deck building and have punched all nails. Do I really need to sand the deck. The boards (Merbau) are starting to go a little grey so I am guessing I am really in need of getting the oil down.

You didn't say how long ago you finished nailing, etc. I'm guessing it
was recently? If so, you need to let the deck weather for at least 6 months
before applying oil. Merbau is a tannin-rich timber, which needs to leach
out thoroughly (via rain, washing, etc) before you apply any oil. If you
apply oil too soon, the tannins and other extractives will rise underneath
the oil over time, and it will turn awful. (I speak from experience. All the
extractives need to come out before you start oiling.)

Are you sure the greying is really the timber fibres going grey from sun,
or is it just dirt and tannins coming to the surface? You can tell this by
giving a small section of the deck a hard rub with a wet cloth. If it
comes up dirty, then it's probably the timber extractives rising. You
can also try using a little Napisan and washing an inconspicuous
part of the deck - to see what difference that makes.

I am hoping that the oiling will rejuvenate the color and look of the deck?

It will seem that way initially, but it will be short-lived.
The dark tannins will rise and collect beneath the oil, making it ever
more ugly over time.

I would leave it to weather for several months. You can accelerate this
process by hosing, etc (subject to any local water restrictions!). Then
try cleaning it with napisan (see other recent threads in this forum).
That will probably be enough. You really only need to sand if any boards
are excessively rough.

If it looks crappy after oiling with no sanding can I still sand it back and reapply oil?

Sure, but I guarantee it will look gradually more and more crappy
after oiling if you don't get the extractives out first. Applying oil too
soon will hinder that process.

The reason I am not just going for the full sand and then oil is time (baby on the way) and have many other projects that need doing before baby due. [...] I want to get it done this weekend (17 - 18 Feb 07)

Abandon that plan. Get on with other jobs for now and let the deck
weather properly for 6 months first. Then clean thoroughly with Napisan
and decide at that time whether any boards need light sanding (as you'll
probably find that the weathering may cause a certain amount of fibre-raising
in the timber). Then start the oiling regime. Explain to your wife that this is the
correct thing to do if she wants a deck that will continue to look good
for many years to come. Premature oiling is absolutely the wrong thing
to do.

[aragorn234]

WOW awesome reply.

I actually nailed the last nail on September 17 5:58

It has weatheredd (until the pergola went up) and I have washed it about 4 times (until water restrictions were brought in)

I believe that the tanins are all out it has been through some rain, washing and sun.

OK I should be nice enough to respond in like to the points made below.

• I finished (as I mentioned) 5 months ago. I left it under advise on this forum to let tanins leech out.
• Graying is occuring more so in the areas that are more sun exposed than the undercover pergola parts,which are also greying just not as badly
• I was thinking sanding for the purpose of a few water marks on the boards. They are not rough at all. I would sand just the areas that need it but I think that would make for really uneven coloring of the boards correct?
• And thanks so ever much for all the great assistance so far.

[strangerep]

I actually nailed the last nail on September 17 5:58

Oh, ok.

It has weatheredd (until the pergola went up) and I have washed it about 4 times (until water restrictions were brought in)

Almost certainly not enough, depending on how many times it has rained
heavily in your area, and whether you squee-geed off the water when the
rain ceased, rather than just letting it sit there until the sun dried it.
The latter will cause tannins to rise to the surface, but not wash right off.
It's really quite hard to wash tannin-rich timber adequately. I've been
finding that I must get out there with a squeeze-mop when the rain ceases,
so that the dirty water is lifted off the deck, rather than being allowed
to sit there and dry.

Also, do I understand correctly that it has not been getting any more rain
since the pergola went up? If so, that might confirm my suspicions about
inadequate washing.

I believe that the tanins are all out it has been through some rain, washing and sun. [...] I was thinking sanding for the purpose of a few water marks on the boards.

The fact that there are water marks suggests that washing has been
inadequate. Those marks come from tannins which have risen in the wet,
dissolved into the rain water, but then been allowed to dry on top of the boards.
They ought to come out if you re-wet the boards, wait a little while,
and then take up the water with a cloth (i.e: try to re-dissolve the tannins, and then
lift them off while still in solution). Also, if you can still cause further
water marks by spilling a little more water on (e.g: overnight so that the
sun doesn't dry it too quickly), that would indicate that washing is
incomplete. If the resultant marks are not too bad, then cleaning the
whole thing with Napisan may be adequate. I.e: try the Napisan
approach to the whole deck before sanding-to-remove-marks. Mop it
off well, and leave it to become absolutely bone-dry before oiling.

Regarding water-restrictions, it may be possible for you to get a one-off
permit from your local water authority for cleaning-before-oiling.
I got one from Sydney Water just by phoning up, but I guess it
will depend on local severities and conditions. Definitely something to
look into if you decide to take the total-clean-with-Napisan route.

I guess all I'm really trying to say is don't underestimate how hard it
is to wash a tannin-rich timber adequately. Sanding instead of washing
is unlikely to be a good long-term solution.

[dan76n]

Great Thread !
I have finished my deck recently with merbau and was soon going to oil it but after reading this I think i will let it sit for 6 months.
Im assuming that the timber wont go grey in this time frame?
I will wash it down with water every month or so aswell (i use a high pressure spayer with a big bin full of water which is legal on the goldcoast).

[strangerep]

I have finished my deck recently with merbau and was soon going to oil it but after reading this I think i will let it sit for 6 months.
Im assuming that the timber wont go grey in this time frame?

The tannins will dominate. If you eventually give it a final scrub with napisan
as described elsewhere, you can decide then whether to give it a light sanding
before oiling. But I doubt that would be necessary - unless any of the boards
are too rough to the touch. Dirt, etc, accumluates more in rough-surface
timber, so it's probably wise to sand off the peaks of any overly-rough pieces.
I now wish I'd been more thorough about that before I put my boards down.

I will wash it down with water every month or so aswell (i use a high pressure spayer with a big bin full of water which is legal on the goldcoast).

Be careful with high-pressure devices - they can rip the timber fibres quite
a bit. I did it recently with a 2000 psi pump and a rotowash attachment.
It cleaned the surface dirt, but didn't really penetrate to the very deep
stains. When I tried using just the pump plus hand-wand, it was really hard
to hold the nozzle at exactly the right distance. Too close and it ripped the
fibres. Too far away and nothing happened.

Remember that the goal here is to coax the tannins out from deep in the
fibres, not blast the timber into paper. This can really only be done by
saturating the deck (not while sunny/hot), leaving it for 30mins or more
(or less if it starts to show signs of drying), and then removing the water
by squeeze-mop. If you have plenty of water from (e.g.) rain gutters, you
could take an approach of re-hosing at intervals to remove the dirty water
and replace with new. Keep doing that until no watermarks remain when
water is allowed to pool on the deck for a long period, - and then do it
some more.

IMHO, it's impossible to wash it too much. The best times
are when it rains overnight, and the deck is still wet in the morning.
Then you can squeegy the water off before breakfast, i.e: before the
sun dries it.

[schwerdty]

Hey, buy a product from cabots called deck cleaner. It is scrubbed on with a broom and will bring back the original colour of your deck. No sanding needed and then oil it. Will look peachy.
best of luck.