Turning decking timber upsidedown?

[Paul Fitchett]

Hi,
My back verandah is covered in a hardwood decking timber - probably merbau. I think it was installed about 20 years ago and the decking pieces are just nailed in to the joists with ordinary nails. Many years ago the previous owners painted it for who knows what reason and it now looks very tatty. I was wondering how to get it looking nice again. The interesting thing about this decking which makes it different from any merbau stock I've seen in the timber yard is that it is not reeded - it has a rounded rectangle profile and is symmetrical top and bottom.

I see two possibilities:

1) Sand the paint off with a belt sander, and then treat the deck with something to bring out the nice colour. But the problem is how am I going to get out the paint that goes down the sides of each piece of timber?

2) Turn each piece of decking upsidedown, sand it and then treat it. The problem here is that I might damage/split the decking removing it, and also perhaps damage/split the joists by having yet more nails go into them. I have taken a few pieces off with no trouble, though.

Does anyone know of a way to handle the problem with possibility 1? Alternatively, is possibility 2 not that crazy after all?

Cheers,
Paul

[jimj]

Dear Paul,

I restore timber decking on the Sunshine Coast and occasionally come across the same scenario. There is always pros and cons in terms of time,effort and costs. You have recognised the issue of the sides of the boards having paint on them. To make the deck look its best you obviously don't want the sides of the boards to have paint detracting from the merbau colour. Either way of just sanding the top or flipping your boards you will have the painted side issue. If you are prepared to flip while the boards are off it wouldn't be much more effort to sand off the paint and then reinstall. The issue of your joists splitting more would still need to be considered but if if the deck is mainly covered by a roof and only receives light blow in rain occasionally I would think it would be OK. Often the bottom of the boards are in great shape except they often have a black mark where they have sat on the joist. You would need to see if that can be easily removed by using oxalic acid or sanding. Sometimes it is just as easy to pull it up and just lay a new deck top. The disadvantage is the cost at about $4.50 lm but you are starting fresh and can redrill your nail holes in different places for your joists. It always seems to be two steps forward one step back. I hope this may be of some help.

JimJ

[Paul Fitchett]

Hi,
Thanks for the information. I've just tried sanding the edges of a painted piece of decking with a suitably coarse sandpaper and it is rather easy to remove the paint from the edge itself - a metre or two a minute, or so.

This provides another possible approach: pop each board up from below just enough to sand the edges, and then drop it down again into the same nail holes. When all that is done just sand the tops with a belt sander. The whole job should only take an entire weekend :)

Where the paint has been worn away the decking is very grey, while it is the new merbau colour on the underneath. Does this mean that if I flipped the decking I'd have to wait six months (and use lots of water) to get rid of the tannins that are still in the underneath part, or are all the tannins gone from the entire piece of wood (as it is so old) and the grey is just caused by the sun exposure?

Perhaps it would be better to sand as described above, apply deck cleaner (oxalic acid), and then deck oil. Can I assume that the deck oil would return the nice merbau colour to the timber?

On another matter, I am extending the verandah a bit with some left-over merbau (also painted and of the same age) that used to form the treads of a wide staircase that went from the verandah. However, I'll also need to get some new merbau as there is not quite enough. Is it the case that I'll have to wait for the new merbau to age before I attempt to oil the whole deck. If so, is there any way to speed up the process?

Cheers,
Paul Fitchett

[Bleedin Thumb]

Try giving it a wash with something that will loosen the paint (caustic soda ?) then use a high pressure waterblaster to take off the piant.
An industrial size blaster -4000 psi should take the paint off no worries.
NB. I haven't tried it myself.

You only need to do the sides of the boards because you can hire a floorsander to do the tops, but I suspect that the blaster is all you will need.

[jimj]

Dear Paul,

As you have discovered there are many ways to achieve the best result and just when you think you have hit on the best solution another roadblock jumps out at you. You didn't state as to the square metres of your verandah decking. If it is fairly large to sand off with a hand belt sander can be a bit like p---ing into the wind. For sanding I use a Lagler Hummel 8 inch belt sander and this is still a bit of work. I use a variety of hand held sanders for all of the trims depending on how hard it is to balance and blend the edges to make it look uniform. The best advice that I can offer is that when you have finally stripped the timber back to bare wood and just hose it with fresh water only if it looks sensational-stunning it will look the same with a deck coating. I am using a water based acyrilic but the coating you use is your choice. All have their positives and negatives. If you strip back the deck and then hose it with just water and it looks like crap in various places or all over no amount of any coating product will make it look better. If the wood feels smooth with no raised ridges it will generally not need sanding. It is hard to make a decision without seeing it but at this stage I am leaning toward just pulling it up and flipping. After some 20 years on an outside verandah I think you have been given a good service from your timber. I have seen many decks with half the service which are in need of just complete sanding.

The highest water pressure that I use on a hardwood deck is between 2000-2500 psi at 12 litres-minute after using a paint stripper. Any higher and you run the risk of physically damaging the wood and then you will be back to sanding anyway.

From the info that you have provided The steps that I would take would be.

1. Flip the boards
2Sand off the edges
3.Sand off the entire deck with a proper floor sander
4. Apply a sodium percarbonate detergent to a wet deck for 20-30 minutes scrub it and rinse thoroughly. This will bring up an amazing amount of dirt and tannins. It is hard to say how much if any tannins still remain but this is really an easy process. You can use Flood Powerlift or mix 200 grams of Napisan with 4 litres of WARM water and stir well for 5 minutes and then spread with a pump spray or use a pad applicator on a pole
5 Apply a 10% solution of oxalic acid and water for 20-30 minutes scrub and rinse well
6. Apply your choice of coating.

If you would like too see what 100% acyrilic water based product looks like please visit my web site at www.restore-a-deck.com.au
I am certain that both more questions and solutions will be brought forward by this great information forum. Hope I have offered a bit more to your thinking.
Jim J

[Paul Fitchett]

Folks,
Thanks for all your advice! It is truly nice to have a forum so useful and friendly!

I'll decide what to do in the next week or so and post my decision.

Cheers,
Paul