The garden sheds of the UK hold a surprising amount of valuable items, whether it's for the garden or for storing items out of the house or for the tools for all your DIY work. Surprisingly not many people stop to consider the value of all these items and can be quite lax in security of their sheds.
What you need to do is to make a list of all the valuable items in the shed and where possible note down any security numbers on the garden lawnmower or other high value items. Then add up the value and you will see that your garden shed is an attractive target for any thieves. Another sobering thoughts is that all the items in your shed are not normally covered by insurance so you need to make your shed as secure as possible. If possible try to chain your valuables items together and this will make it more difficult to get these items out of your shed in the first place.
The most basic thing to do is to ensure you have a good lock on the shed door, and to USE it, when you are not in the garden. A hasp and staple, and preferably the hasp and staple where the hasp folds over the screws, coupled with an heavy duty padlock is the best type of locking arrangement. This will protect the screws from being unscrewed. You will find this can be better than a rim or mortice lock on the shed door. The reason for this is that the gap between the shed wall and the shed door can be prised open allowing the bolt to be ineffective.
I would then suggest that the hinges in the shed door have at least one nut and bolt through in to the shed, in place of the screws. This will mean that the shed door can't just be unscrewed. It's always a good idea to have a curtain across the shed window as this will stop any opportunist persons being tempted. And ideally the addition of bars across the shed window will protect this are from a break in.
You can also help a garden shed alarm which would give out a loud noise if any intruders get in. Might not stop them stealing some of your items but could scare them away sooner than they would have done. Passive infra red security lighting is another deterrent but be aware that cats and foxes wandering about in the night will trigger these as well. I know as many a night I woken up with the lights on down the garden because of these animals.
The addition of thorny bushes and gravel will also make your garden shed less attractive to any opportunist thieves. The bushes making them more likely to be hurt and the gravel will make their entrance more noisy and noticeable. Always, if possible, ensure there is a locked gate into the garden as this will stop these thieves getting anywhere near your shed in the 1st place.
If you want to have the highest level of security then take a look at the SafeStore steel security sheds. These come complete with a steel base so when assembled are nearly impossible to get in when they are locked. These steel sheds are make up to high insurance standards from steel which is 1.2mm thick - over 4 times thicker than the normal basic metal garden shed - and have a reinforced steel section on the doors. Many of the SafeStore steel sheds are fully approved by insurance companies to give you complete piece of mind.