Both of my bikes where stolen two months ago for what I though was a secure setup. Since then I done a lot of research and now have spent a lot of time and money improving my setup.
My original setup was padlocked ‘Trimetals
Cycle Store’ with a mid-priced ground anchor and lock (sliver standard). Behind a 6 foot fence down the side of the house. This setup was attacked twice. Originally when the bikes were stolen then 2 weeks later (the thief came back looking for the replacement bikes, very common). The first attach the managed to unbolt the ‘Trimetals Cycle Store’ while locked (easy when you know how I tried it myself after bolting it back together) the second time they just cropped the locks. Any padlock under £40 can be cropped in seconds with a cheap bolt croppers.
I personally would never leave a bike in a ‘Trimetals Cycle Store’ again (I now store garden tools in it) but you can improve its security (which I have done). Replace the nuts with ‘Shear Nuts’ (size M5) so you can’t just unbolt the shed. You can also lock the Trimtales using ‘Oxford HD Bike Cycle Mini Shackle Disc Lock - 10mm x 10mm’ (it’s like a mini D lock).
I now use an ‘Asgard Bike Store’ it appears to be a better design than the ‘Trimetals’ but this has never been tested. It’s also installed in the back garden under our bedroom windows and fitted with a £5 shed alarm. The bike is locked inside the Asgard with an ‘Abus WBA100 Ground Anchor’ and locked with an ‘Almax Series IV Uber + Squire SS65CS Lock’ chain. The Almax chain is a thing of brutal beauty and designed for locking up motorcycles. The Almax website’s ‘wall of shame’ is worth a look they have video of them cropping most high end cycle locks in seconds (Kryptonite Fahgettaboutit and Abus Granite City Black X-Plus both in less than a minute).
I’ve also done additional steps of improving my security lights and installing CCTV.
All the above may seem extreme and it was a large sum of money. I’ve come to the conclusion that nothing is 100% secure but your either spend hundreds on security or buy a £5 cable lock. The £5 lock will stop an opportunist walking off with you bike any lock sub £150 can be beaten in seconds with something as cheap as £10 hacksaw.
So to answer the question the only thing the shed will do is keep your bike dry.
If this wasn’t depressing enough watch this video.
http://www.pinkbike.com/video/266500