To preserve outdoor wood . . . or not?

[Eddy Bentley]

Hi All,

Your advice would be appreciated.

I've just bought a house with lots of decking - the sort you buy in planks at Focus, and probably other DIY stores too. The previous owner has told me "all it needs is a pressure-wash twice a year".

However, every time I pass all those different pots of wood preservative (Light Oak, Dark Oak, Forest Green, etc.,) I wonder if I should be slapping some on all my decking, outside stairs, railings, and the like. Or are the preservative-makers just out to take us for a ride.

Firing a pressure-washer twice a year over all the wood is likely to be easier, I think, than carefully painting every inch every . . . how-many-years?

What do you think?

Thanks.

Eddy.

[Andrew Mawson]

preservative

Pull it all up and put down a decent flooring of stone or imitation stone. Decking looks awful, goes slimey green after a few years, then you put your foot through the rotten bit. Rip it out and replace with a proper surface and in years to comes when people talk about decking in the same tones that they do about avocado baths you'll know you did the right thing.

AWEM

[Eddy Bentley]

Er, "thanks", Andrew, but to rip this lot up and replace it all in stone . . . that would cost an ARM and a LEG! Anyway, this decking has been down for two years already and it seems not to have gone a slimey green yet . . . though, admittedly, there are bits of green here and there. But that's probably because we've had a hell of a lot of rain recently and it has been pressure-washed recently.

Actually, all the decking around this house has been remarkably well done and its a pleasure to look at and use. The question is: how best to preserve it?

Eddy.

[Andrew Mawson]

imitation

there.

recently

Well without ripping it up (the kindest thing to do for future generations!) you will only be able to give is a superficial coating in the areas least in need. The water will sit/soak in where the decking sits on the joists. Both hopefully were pressure treated before laying the deck, and there is no way you'll get your preservative in there without dismantling. Anything else is only slightly delaying the inevitable decline into a loathsome slimey mess If you don't do the nice thing and rip it all out, at least ensure that there is good ventilation from at least three sides

AWEM

AWEM

[Brian G]

Eddy,

Quite simply if the boards are of good quality tanalised timber, then it should last a minimum of 10 - 15 years before beginning to rot - even if left untreated.

If you want it to look pretty at all times - or even try to extend the life of it - then give it coat of 'whatever colour you fancy'.

With regards to "are the preservative-makers just out to take us for a ride" then the answer to that is generally no - particularly with the good quality stuff.

As a matter of interest, I use Sadolin (at £30 a 2.5ltr tin) to coat my shiplap garden shed with 2 coats minimum and this will last at least 5 years before needing a recoat - with minimal repair works to rotted or damaged boards.

Brian G

[Anne Jackson]

Yeah, great idea. Because of the slope of my garden, the decking in front of the summerhouse is about four feet up in the air... don't you think stone. slabs, etc. _that_ high up would be just a tad dangerous?

[Anne Jackson]

The message from Eddy Bentley contains these words:

I was told by the installers of my decking that it wouldn't require any maintenance for ten years, so it would depend on how long ago yours was installed, would it not?

[The Natural Philosopher]

I liked avocado baths....

[The Natural Philosopher]

Nah. Let nature do its work.

May look better with a coat or three of whatever replaced creosote, every few years.

[Anne Jackson]

The message from "Brian G" contains these words:

How big is your shed? I'm just trying to work out how much it would cost to coat a 10' X 8' garden shed, and a 14' X 8' summerhouse, plus 8' X 6' of decking...twice!

BTW which Sadolin did you use? There's a lot of different types, is there not?

I see the Sadolin Quick Drying Exterior Woodstain is available for £22.48 (inc VAT) on their site. Their Sadolin Classic Exterior Woodstain is 2.50 litre £22.38 and the 5 litre size costs £41.78. That might be the best bet, for me...

[PJ]

Cleopatra preferred asses milk baths. They probably had fewer stones. ;-)

[The Medway Handyman]

Utter tosh!

Decking great & provides a much nicer surface than stone ever could. Decking is no more slippery than stone either and provided it was pressure treated will last 30 years +.

Avocado bathrooms? What about pink & yellow slab patios?

Simply pressure wash or use decking cleaner once a year.

Decking treatments protect the timber from dirt & stains and stop the UV light turning it a silvery grey colour. If it was pressure treated it is effectively 100% resistant to rot & insect atack.

Decking oil is my favourite treatment, looks natural & easy to apply.

[Andrew Mawson]

imitation

decking

could.

apply.

...ah ... an unbiased opinion from one who makes a living installing decking perhaps Decking in most situations is appalling, unsightly, and limited in the longevity stakes.

AWEM

[Andrew Mawson]

imitation

decking

If you fall off decking from four foot up it must be very similar to falling off a proper terrace of the same height ! I am aware that decking adversely alters the aesthetics of the locale, but I wasn't aware it also affected gravity Any terrace, whether decking or a properly constructed paved one should have either a series of steps or a ballustrade if four foot high at the edge.

AWEM

[Tony Williams]

I don't know about towns, but decking in country areas seems to attract rats. Brings them too close to the house for comfort, and those open patio doors.........

[mail]

Dear Eddie Tanalised timber at say 4 kgs per cub m should last 50 years (min) if not in ground contact. Tanalised timber to (I think 8kgs/c m) is designed to last 50 years in ground contact when used as motorway fence posts and in the case of the M 1 I understand have performed to standard. IF

1) none of the decking is in gound contact (or the supportive elements are isolated) 2) any cut ends exposing the non-tanlised timber have properly been treated then the wood should see both of us out out lifetime and probably our kids

With respect to washing ..... I am confused but presume that this is to prevent accumlation of algae etc If this is happening I suspect you have not got the right water repellent presevative stain on the surface to stop this and I agree with the other post that to put on saddolins would do no harm and would only be needed to be done every 18 months to 3 years dependant on the weather and use.

I would look at the structure and check how it is supported relative to the ground and put my efforts into treating or attending to that location. If, for example, there are tanlised posts set in the ground THAT is where the risk is at the interface at ground level and were I to do anything it would be to put a pea shingle bed around the top 150mm of post where it meets the ground. Chris

[Anne Jackson]

*WHOOSH*

[Eddy Bentley]

Many thanks to all posters, so far, who have given really helpful info about preserving existing decking.

Having just moved in, one of the first jobs I've done is clear away grass and earth as much as possible where they come into contact with the steps (made out of decking) which lead from the road up to the house. Doing so, I've noticed that that wood in contact with the earth is not in as good a condition as that which is surrounded by air. Unfortunately, I can't do much about the ends of the supports which have needed to be driven into the ground - although maybe I won't water adjacent plants so much as others!

From what most of you have said it seems that, indeed, pressure-washing should suffice. It certainly seems to have kept the wood generally clean so far.

Aesthetics has a little to do with my question. All the decking here (including steps, railings, stairs and ballustrades), having never been coated and only pressure-washed, is grey in colour. There is thus a clash between the colour of the decking and the colour of the varnished honey-brown window frames. We're inclined to coat the decking in honey-brown too, to achieve visual harmony. However, from what people have said here it sounds like doing this won't add much to the life of the decking.

Can I ask you all if there really are big differences between the different pots of wood coatings/preservatives? We bought a large tin of some "Forest Green" stuff the other day to make an unsightly trellis disappear into the greenery behind it . . . and it only cost £5. However, people here have mentioned Sadolins at £22 (approx) a tin. IF we're really only talking aesthetic effect (colour) at the end of the day, in using this stuff, then are there good reasons for paying £22 a tin instead of £5?

Eddy.

[The Natural Philosopher]

Tsk Tsk. Never get THAT past building regs. Ought to be a wheelchair ramp.. ;-)

It will if you do it every year. And believe me,it will need it.

Exterior varnishes don't last.

I've been VERY diappointed with sadolin.

[mail]

On 6 Aug, 10:41, Eddy Bentley wrote:

Eddy you need to differentiate between a wood preservative and a wood "paint" or covering A preservative is designed to get into the side grain of the timber with an active ingredient such as permethrin or cypermethrin (for insects) and a variety of organo-metallic compounds for fungal decay or simply boron based compounds. ONLY pressure treatment in a water based Tanalith (what used to be CCA treatment) will chemically combine with the hydroxyl groups in the timber to form a pretty permanent fixation. All OS borne (eg vac vac) and aquavac treatments only use a carrier fluid to get the active ingredient is as far as it can - which depends on the porosity of the wood (a natural feature) and a variety of other factors. Thus ANY site treatment is limited in it efficacy PARTICULARLY if you are going to pressure wash it every year! So, given that you are treating already treated timber (tanalised) all you need is a good water repellant preservative stain. You have a choice of low medium and high build. There are data published on these by BRE. Based on personal experience over 30 plus years I now do use Saddolins and just re coat every few years. the advantage is that it "chalks" and you dont have to scrape off the old layer as one does with oil-based paints. There are much cheaper water repellent stains on the market but I have found them unsatisfactory for windows - which is what I use them for but you may well find them fine for decking so I would try them both in different areas and see how each lasts. Let me know in 12 to 36 months' time! Chris