In the USA, basswood is often used for shutters.  It is straight, strong, lightweight and has a very fine and uniform grain.  It sands to a very smooth finish and is very easy to work.  Takes both stain and paint well.

I don't know if you can get Rockler products in France, but they have several new kits for making shutters. These were just released a couple weeks ago. They include an on-line (design wizard) program for designing your shutter parts, and also the parts to make the shutters, and jigs for drilling/mortising. They also include some Really, really, really good instructions with the jigs...not that I would know anything about the instructions.  

The different kits include the necessary jigs. They also have the pins for movable or fixed shutters, and control arm clips for movable shutters. You can even buy the bass wood components that are pre-milled for the slats, stiles, and rails that you cut to length for your design. They also have the full set of router bits for milling your own stock.

http://www.rockler.com/c/plantation-shutter-program.cfm

I don't know all of the in's and out's of this new product, except it was created as a complete system (or as separate components if you wish). Yes, I did begin writing the instructions, but with a sudden last minute schedule change, I just turned over all of the text and artwork to Rockler for final processing. (The schedule got bumped forward to release before Christmas.)

I think the various forms of Cedar are what's often used in the US for this.

Cypress is also a good choice for exterior applications.  Guttering was made from this wood for many years and it stands up well to moisture and can be painted.

Thanks for the replies
They'll be traditional 'barre et écharpe' - braced with diagonal supports. The problem is the client wants chestnut and wants it painted. I've tried suggesting other solutions. I quoted fairly high for the job as I don't like the idea of painting chestnut and buying the planks will be expensive, but I am afraid I need the work.
If the stock will move after its cut, will 34 mm planks be enough to give 28mm finished section?
I am also concerned that my cutters aren't adequate. What length tongue / groove do the experts think I need? Someone said yesterday that with the terrible climate here an 8mm tongue was not sufficient. I would have thought that if there was more movement than that the things would fall apart anyway.
Thanks in advance,
Richard

I am curious why your client wants chestnut so adamantly if it is being painted. Did they give a reason? Personally I'd go with cypress.


Seth

Richard,


Hmmmm, didn't think about availability issues.  Fir? 


Seth

There is an excelent reason for chestnut and that it is one of the most rot resistant native woods you can get. Its life span, without any treatment, in direct soil contact is double that of oak. You can get 80 to 150 years and more depending on post size  All the best wire and post movable fences are made from chestnut and have been split with a froe. It is still produced and used today in Britain
http://www.jacksons-fencing.co.uk/fencing/agricultural-fencing/cleft-chestnut-fencing/agricultural-fencing-cleft-chestnut-fencing.aspx http://www.torryhill.co.uk/chestnut-fencing.aspx
 Certainly when green it splits beautifully and easly. When I was still in England full time I helped coppice chestnut and construct green chestnut paling and post fences that have now been in use for over 40 years out doors untreated and are still in use today.

I can't comment on how it works when seasoned or cut as I only worked with the green wood and only ever used a froe, apart fom a chainsaw to cut it to length an an axe to put points on the palings.

I would expect that, that is the reason why it is a traditional wood to use. Country side French are not stupid despite what we say about their letters.

No one round here sets the 'barres' into the stock like in your link (which I found a while ago and think is very interesting) It is perhaps a good idea though. I just worry that it might increase the risk of water ingress. Generally shutters here rot wherever water has a chance to accumulate.
Rchard

Richard:
Interesting. Jerome seems to have covered the rot resistance issue. It was something (setting the barres into the stock) I was curious about after seeing photo's of the "commercial" ones online.
I suppose the cut in keeps the boards flat to the frame through the huge swings in temperature from direct sun during the day to cool evenings. I do like the angled detail on the barre and I suspect that sheds a lot of water. I would be more worried about the condensation and mold developing on the back of the boards because of the difference in temperature from the front of the shutter to the back.
Tim