Home Greenhouse

‘Stability’

I’m putting the plans together to build an attached greenhouse that will sit on the south side of my house. It will be a 12′ x 9′ x 10′ structure. I’m using another smaller plan that I saw someone use and modifying it a little bigger. It’s pretty basic. 2, 12′ wide by 10′ tall east and west walls and 1, 9′ wide 10′ tall south wall. The north end will be attached to the side of the house. The roof will rise will rise up an additional 4 foot.

My question is, do I need to use 2×4’s for all of the studs to ensure a firm structure? Smaller houses use smaller wood but I don’t want it to crumble down.

Here is the smaller plan. http://www.buildeazy.com/greenhouse2.html