Weather groove in Weatherboard

[mayerk]

We wish to use Tas Oak (Macrocarpa) horizontal bevel-back weatherboard on our house and have read in a Brantz (NZ) timber cladding guide book that a weathergroove is highly recommended to stop water moving up between the laps and making the weatherboard.

For extreme locations they suggest a 4x4mm routed groove on each board to line up with eachother inside the lap. (so there is a goove on the back face of the top (lapping) board (near the bottom of the board within the lapping section), and a groove on the front face of the bottom (lapped) board (near the top of the board within the lapping section). So when they are lapped the grooves line up to make a 8mm deep x 4mm weather groove.)

For less extreme locations (like ours) they suggest that just one weather groove can be used - but they say just the one on the front face (at the top) of the bottom (lapped) board is all that is required (on the front face near the top of the board within the lapping section). However, this seems to mean that if water is driven up through the lap that it will collect in this groove and seep into the board which extends below it, and perhaps cause movement...?

The board is there to stop weather getting in, but they just do all this movement, bowing and warping, especially with water and sun.

So the question is: Does anyone have experience with weatherboards with a weathergroove? And do you know where, and if a weathergroove should be used so that it keeps out the water but doesn't warp the boards?

Thanks,
KEJM

[barnsey]

KEJM

I'm no builder but I've owned three weatherboard houses and never seen such a thing.

My old man built his own weatherboard house after the war and his sole recommendation was make sure you prime and undercoat the boards both sides before you put em on. His house is still there after nearly 60 years in Melbourne so I guess it was good advice. Pain in the butt when I had to do it when I put an extension on a house in Brunswick but once it was up the topcoat was as good as the day it went on after 5 years.

My 2d FWIW

Jamie

[mayerk]

Thanks for your help Jamie,
I does seem that this weathergoove is unheard of. Painting is definitely the thing - painful but necessary.

What's FWIW?

KEJM aka Kirt

[DaveInOz]

FWIW

For What It's Worth

[barnsey]

Thanks Dave:p

Kirt - Happpy brush slapping:rolleyes:

[mayerk]

Hi Jamie,
BTW, your top coat that lasted 5 years, was it oil, even Tung Oil, or was it waterbased? We want to put on a light stain instead of an opaque paint.

Sickkens seems highly recommended, and it has some weathershield, but it isn't oil based so I wouldn't expect it to penetrate the wood and flex with it as it weathers. The problem with straight Tung Oil is it doesn't seem to come mixed with any UV protection so I'd just be relying on the tint of the stain for sun protection.

Regards,
Kirt

[silentC]

Kirt,

Don't be too quick to write off the weathergroove idea. I'm certainly no expert on weatherboards but I do know that water has an uncanny knack of travelling up hill when it can get a grip on two parallel surfaces. The idea of the groove is evidently to break the 'tunnel' that is formed between the two boards so that the movement of the moisture is stopped before it gets to the top of the bottom sheet.

I'm sure someone could populate that paragraph with technical terms. Whether it has any applicability to your situation is one for the experts.

[barnsey]

Kirt,

Mine was Dulux Weathershield that was tinted to match some cladding on the balance of the house. Frankly the prospect of having to paint too often made me go for as durable protection that was about at the time. Afraid I can't comment too much on what you want to do - it's an unknown to me. Can only say that on the boat woodwork I go for the best quality marine clear that I can find/afford and it still needs refinishing every couple of years or so at best.

My only suggestion is ask lots of questions at the paint store or stop and talk to a professional painter if you can find one and ask them.

Good Luck.

Jamie

[mayerk]

Thanks Jamie, Dave and SilentC,
Yep the propspect of any painting drives me to want to use colorbond on the walls so I never have to touch it! But my partner wants weatherboard, so after installation, the brush slapping will be all his to enjoy.

Regards,
Kirsten