I am renovating my home which is a 1928 calbung and adding an extension and am shopping around for top quality weatherboards.Can any body give me tip on what would be the best boards to use and why.

I don't think you have a lot of choice. Baltic pine is about it but one thing i did when i replaced all my boards was to seal all the ends on the timber with SikaFlex. I used 11LM which allows for expansion and contraction. If you look at old homes and where they rot its 99% of the time at the ends. It doesn't cost a great deal and with care is a pretty quick process to do. I know as i did about 2 km's of boards.
If you want to know more just send me a PM

You only have a couple of choices for real weatherboards.
Baltic pine is available in square edged or round edged.
Western Red Cedar, usually only avaliable with sawn finish and square edge.

Then there are "imitation" weatherboards made from cement sheet or tempered masonite.

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Regards
Bob Thomas

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What type of boards do you have at the moment . Try and match like for like. If you have pine use pine. If hardwood use hardwood. I did renos on my place and had 175mm hwd and bought second hand boards and sanded them back . came up like new. Ive seen many houses mix pine and hwd and it just doesnt look right.
Just wanted to check as well that they are actually weatherboards and not chamferboards. Many of the older style houses up here were pine chamfers.
Good luck with your search anyway.

If you're matching boards pay attention to how the new boards are cut as well. I had some boards installed that were not cut with a circular saw (band sawn?) and they had vertical saw marks and really stood out against the original boards. Thankfully the builder screwed up installation and nailed the top board through the bottom board and two weeks later they all split and had to be replaced. The replacements were sawn using a circular saw and are almost indistinguishable from the older boards. (This was the only positive out of the whole affair - it took two years or wrangling with the builder and the BSA to get the boards fixed!)