Exterior timber

First post so go easy on me

Long story short, I'm looking to build my own shed and want to save money in the process. My thought/plan is to purchase wood like this and then use the router to cut them like the attached image. Is this wood suitable (once treated) ?

Time isn't a problem as I already have a shed but it's getting old now.

Also, has anyone ever taken a standard shed 8 x 6 and extended it ? I always have timber and tools getting in the way and I usually have to empty the entrance before I can even get in.

Any other money saving ideas are more than welcome!

Thanks

Personally I'd go for ready tanalised timber, but there's nothing wrong with your proposal......always best to buy timber from a genuine timber merchant if you want quality stuff!
A tongue and grooved moulding would prevent warping better.
John

As John say, make it out of tanalised, and have a shop around the local timber merchants see what they have on offer.
You can extend a shed, but you need to put some sort of frame in to strengthen the area where the join is, as taking the end away weakens the structure.

+3 pre-treated.

Feather-edge cladding is generally as cheap as it gets.

Feather edge is about a quid per length.