Painting Red Cedar weatherboards

[misspage]

Hi there,
Just wondering if anyone could give me some advice re: painting western red cedar weatherboards.
We are currently doing an extension on our existing red cedar clad house, with the new extension being red cedar also. We are painting the boards with an exterior paint, not a timber stain.
We are preparing the boards with the white oil based primer (Haymes) followed by two coats of the low sheen exterior paint (Haymes).
We have had conflicting advice regarding the surfaces of the weatherboards to paint.
Some timber people are telling us to paint the whole surface of the weatherboards, whereas the paint professionals at our local hardware store are saying only to paint the exterior face of the weatherboard and the underside (not the back or edges)as too allow any water at the back of the boards to get out of them and not be trapped in by the paint.
Obviously we are wanting to preserve the timber but also the paint finish. Just wondering what adive you would give as to how much of the weatherboards to paint?
Look forward to your reply,
Emily Collins.

[Fossil]

You are best off priming all of the boards back front, top bottom before you install. Prime any cuts that you make while installing as well. WRC bleeds through paint badly, if not properly sealed first. It is obviously more work, but you will end up with a better job.

If you add some tint to the primer to get more of a grey colour, it will cover better as well.

[echnidna]

Paint the front only and just a narrow strip on the back where the boards will overlap.

If you paint the whole board and moisture gets in, which it will eventually,
the timber cant dry out easily and this will cause dry rot.

[Fossil]

Moisture will get in by virtue of the back of the board being in contact with the moisture/vapour barrier... ie.. Sarking.
Have a look at homes that are painted after construction, and not on the back of the board. You will probably see that the board has cupped out. This is because the back of the board has teken on the ambient moisture in any wall, and has expanded accordingly. It is more work to paint all of the board, but worth it IMO, although the majority of jobs are done using echnidna's method, As I have done in the past as well. Not as good though.


timber cant dry out easily and this will cause dry rot

Sorry there mate.... You are dead wrong on that one. Firstly, there is no such thing in Australia called "dry rot", only rot that has since dried, which is where you may be getting confused.

Secondly, Western Red Cedar has a ground life of 24 years in the eastern states of Aus. That is........ the good stuff will not substantially rot away for mre than 24years in contact with the ground. There is no real issue with WRC weather boards rotting away, because they are painted, which is what I think you are implying.

Sorry echidna....... I was a TAFE Building and Construction teacher for a good many years, and these are two things that I do remember. :)

[echnidna]

Fossil,
I don't intend to get caught up in a pedantic argument about dry rot.

So I will merely amend the sentence you found incorrect.

"If you paint the whole board and moisture gets in, which it will eventually,
the timber cant dry out easily and this will cause the boards to rot away."

Still means the same thing though.

As for the boards cupping out coz the backs weren't painted. ---
The old Victorian house I'm currently renovating has the odd cupped board.
There were some brand new unused boards left behind by the previous owner and guess what- some of them have cupped out too and they have been painted all round.

I beg your foregiveness Mr Tafe Teacher,
I was merely a Master Builder in a previous life so I suppose I must know nothing.:D

btw, I've seen WRC rot away within a few years.
Ive replaced the odd rotted wrc window too.
I expect its the sapwood that rotted, but are all wrc weatherboards totally free of sapwood? I dunno.

[Fossil]

First thing.... a very deep breath. :)

Hi echidna,
I am am member of the Master Builders Association as well, however that doesn't neccesarily make me, or any other member, a "master builder". Skills and experience does.
Sorry to offend you, but you were wrong. I could highlight the misinformation but couldn't really be bothered.


I beg your foregiveness Mr Tafe Teacher
I bet you were a naughty little boy in class. :)

I did not notice when I previously posted, that you have made over
6 trillion posts here. These pages are obviously a big part of your life, so I am sorry that I offended you.

My previous post stands.... unedited, as my informed opinion.

[Pulse]

So misspage,

you said you had received some conflicting information.....

[dapainter]

Ok, if you intend to paint the whole board, make sure that you allow all of the timber to dry out first. if you dont the timber will actually also cup.Now the hard part is knowing if the board is fully dry. As a painter i have been caught out a couple of times with painting the whole timber while it was still a little wet (unknowingly)... the moisture could not get out and the the timber bowed. If you are comfortable the timber si dry, paint the whole lot!!

as general rule of thumb, you do not need to paint all sides. front and sides are sufficent!!