Cedar weatherboards

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Disrespective

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#1527835 7-Apr-2016 18:11

mattwnz:
Disrespective:

mattwnz:

You can just let it go natural,
This is not the best advice. You need to be very careful of cedar in our environment. In Europe the cedar used is very clear and free of knots and can stand up to exposure and consequent silvering much better. Here in NZ our cedar can be quite knotty which when combined with our harsh sun and often coastal environments can cause these knotts to pop out and create holes in your cladding. The knotts don't even need to pop out completely to have serious consequences to the weatherproofing of the building. An oil or paint system is definitely recommended for any cedar cladding in NZ. YMMV

I have never seen 'knotty' cedar being sold, as it is all imported as far as I am aware. If you are getting knotty cedar, it will be seconds, or it may not be the quality western red imported stuff. New cedar for cladding should be sold in 'clears' , and shouldn't have ANY knots in it. We have had cedar weather board unstained for decades,(no knots) as it has natural protectants in it, and looks as good as new now it has been stained. Staining doesn't really provide much extra protection, becuase if there is a knot and gap, water will still get in eventually. Painting and fiiling the holes is the only way to stop that. You maybe referring to macrocarpa, which can be knotty. Usually it is installed on a cavity with wrap behind that anyway these days. The thing is most claddings can leak to some extent anyway, that is why there has to be ways for the water to drain out. It is becuase water couldn't get out , that was a contributing factor of the whole the leaky building thing, which is why most cladding now requires a cavity to allow water to get out from behind the cladding. Anyway, the local TA will tell you what is and isn't allowed anyway when it comes to cladding.

I definitely mean cedar, we specify it on almost every job we do. (am an architect)

Older cedar is better than some of the newer stuff but don't assume everything is clears.

mdf

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#1527885 7-Apr-2016 19:10

dusty42:

Interesting responses all - thanks.

The house is 50 years old and has rough sawn cedar - stained with a Cabots deck oil by the previous owner.I was just wondering if anyone here had tried to go from oil->stain or stain->oil

Interesting experience Andrew027 on the freqency of cedar staining your place.

I can see some cupping and lifting on the face of the house which catches morning light - so the timber is overdue for another coating.

I had expected to eventually get a water blaster to use on the house - yeah cedar is soft as warm cheese, but all the cleaning systems say to use pressure washers to remove, just really really carefully I guess.

How old is the existing stain? If it's real old, you should be fine regardless. Failing that, do you have a reasonably hidden spot you could test something on? I'd probably stay away from the waterborne stuff if you're going over oil. I'd definitely suggest some expert advice. As I mentioned previously, Resene has a technical support line that is really really helpful.

mattwnz

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#1528081 8-Apr-2016 00:03

Disrespective: I definitely mean cedar, we specify it on almost every job we do. (am an architect)

Older cedar is better than some of the newer stuff but don't assume everything is clears.

Ditto, that is why I specify class 1 clears and reject any with defects. Just had some installed on my brothers house and it is all perfectly clear.

Hammerer

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#1528832 9-Apr-2016 00:03

A lot of people have to replace their cedar weatherboards or have them painted within twenty years. The cheap cedar they bought proves to be very costly. Three or four times a year I hear about people with this problem in my area. In the last 10-12 years it has happened for three houses on my block.

All cedars are not the same quality and much of the cedar installed in New Zealand is not suitable for leaving unprotected and some is not very good for use on building exteriors. Maybe some people have used unsuitable sapwood but even with heartwood cedar there are many people regretting its use. There are differences in the chemical composition and density of slower-grown timbers that were more likely to be used decades ago versus the the faster-grown timbers that are more often sold in our time.

One issue with using cedar, e.g. Western Red Cedar (thuja plicata), is not an issue with the wood per se but with how people think it can be used. Many users including some builders do not realise the difference between decay and degradation. Cedar is usually considered to have naturally high resistance to decay/decomposition (slow breakdown, rot) which users assumes mean that it also has high resistance to degradation (damaging or ruining). It doesn't take damage well as it is a soft wood so it is easily degraded by, for example, water blasting as has already been mentioned.

Compare the stats for cedar versus macrocarpa. I prefer cedar for the smell and colour but the smell soon goes and stain can give me a similar appearance with other woods. Macrocarpa would win for me, even with a greater tendency to split, because it has borer resistance.

dusty42

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#1547828 6-May-2016 21:20

For the record here is the best advice for restaining cedar weatherboards I've found - http://www.resene.co.nz/pdf/painters_woodcare.pdf - page 4

tl;dr: Keep same colour or go darker. Resene Waterborne Woodsman: very tolerant of weathered and poorly prepared timber.

MinisterOfChooks

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#1547943 7-May-2016 11:00

I had Cedar on the north part of the house, it was wearing well, 15years no maintenance, one small part (end grain) was exposed to the weather and the oils were washed out, the timber rotted & had to be replaced.

So don't allow water to wash out the oils. Once you start using stain it becomes a regular event like painting

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Martynnz

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#1547984 7-May-2016 14:02

We have this same debate with our house. We went down the cd50 path. I used a pressure washer to clean it with their recomended product (which i am sure is dishwashing powder). I have a petrol washer. I brought a set of nozzles for it off ebay that lowered its pressure to 800psi (you work out how many gallons perminute your pump puts out and then the desired pressure. There are tables on line which diameter nozzle to get).
Applying cd50 fine and happy with early look. Given this was going to be a multiple application project going into the future I got an airless sprayer from wagner. Makes applying the cd50 easy as you spray it on quick and the spray gets under the edges. Painting with a brush was a long and painful process.

dusty42

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#1549164 10-May-2016 11:55

Martynnz: We have this same debate with our house. We went down the cd50 path. I used a pressure washer to clean it with their recomended product (which i am sure is dishwashing powder). I have a petrol washer. I brought a set of nozzles for it off ebay that lowered its pressure to 800psi (you work out how many gallons perminute your pump puts out and then the desired pressure. There are tables on line which diameter nozzle to get).
Applying cd50 fine and happy with early look. Given this was going to be a multiple application project going into the future I got an airless sprayer from wagner. Makes applying the cd50 easy as you spray it on quick and the spray gets under the edges. Painting with a brush was a long and painful process.

What sort of condition where your boards in Martyn? What was the previous coating? You've done what I've wanted to do, for sure - unfortunately our place was last coated with Aquadeck which leaves an acrylic surface on the boards - no way to get them clean without getting a big crew in.

lol @ Sara Clean - I have a few packs here. Potassium perchloride - I think it's actually Nappy San/napisan. It does work and it is gentle enough I don't mind practically bathing in it. But next time I'm just using whatever I have in the laundry - this is supposedly a real thing and is something I picked up off a rennovation forum.

I'm brushing my place - done about 15L of stain so far and more than that to go. Real PITA, which Wagner would you recommend for this type of project?

Martynnz

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#1549206 10-May-2016 12:33

My weatherboards were just weathered with no previous coating. A few looking worse for wear with cracks etc but they reckon it should settle a little with oiling.

I sympathise with regards to having to use the paint brush. I did some of ours with it and it was painfully slow. I coated the garage in about 30 minutes with the sprayer though you do need to spend some time masking windows etc. I brought the wagner project pro 117. A little bit expensive but figure after I have done it twice I'll have paid for it. You also need to get a fine tip (410FF) for the spray pattern. I got it all through Millin distributors who were good to deal with and good price.

I'm currently on hiatus till I can get some scaffolding to do the front (which is 3 storeys high in some points)!

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