This is easy... Price should come down to quality, as the fixed costs should be roughly the same. The fixed costs being manufacture, delivery and assembly (wages), along with hidden costs such as insurance, tax, rent and rates, electricity, advertising and other bills. After that, you are looking at the difference in the quality and amount of materials involved in production. Therefore, if you buy cheap, expect cheap. You might find that the reality might not match the picture, but if you're happy for something to last only a couple of years then buy on price. If longevity and quality are more important, then be prepared to pay a bit more for a better product, and have it installed. Furthermore, adding extras such as guttering increases the longevity too. 

So you're buying a wooden shed, and on the face of it, all sheds should be the same right!  

Wrong.... firstly the timber can be (FSC) sustainably sourced - or not (which is not very environmentally friendly). You can have hardwood, softwood - redwood or whitewood. Planed or sawn - Baltic, Scandinavian or Home Grown. So which would you choose if you had the option?

Would you also prefer Tongue & Groove, Shiplap, Feather Edge or Loglap? - Treated or Untreated? And would you prefer a building that has fixings or is just slotted together?  TIP: Stay away from those if you can as the windows move up and down by hand (to allow for expansion & contraction),  and the corners open up for for spiders to crawl in.

Most people know what size they want, especially if they are replacing and old shed with a new one. If however, you are starting from scratch, simply measure the gap you have between available, or put the items you want to store in the area, and measure that size. If you allow 150mm away from the fence or wall, you will be able to determine the best size for your needs. The sheds usually have a small roof overhang of about 100mm so take that into account if slotting in somewhere tight. If it's an odd shape, send a plan sketch of the floor dimensions to us, so we can provide a quote for the closest match. Corner buildings look like a great idea, but they do lose quite a lot of internal storage space, so it's best to have square or rectangular if you can.

OK - so it's only a garden shed - but I'm presuming you don't want to waste your money? 
Low quality sheds use white wood, as it is grown quickly and is therefore the cheapest. The speed of the growth means the wood has large gaps between growth rings. The down side to this is weak structural strength and massive expansion and contraction scales. 

Redwood (see above) has red coloured growth rings that are much tighter together, providing much stronger timber. This timber is often used for construction and is graded. 

Hardwoods, usually take longer to grow hence they are much more expensive. They're not often used for garden sheds, unless you want top of the range Oak or Cedar cladding.

Scandinavian redwood timber is graded at source either manually or by computer, so that each piece of wood can be used for it's best purpose. Baltic states however take a different approach and the pack of timber is not always consistent throughout. This could result in your building having poor quality timber full of splits and knot holes. The difference in grades determines the knots and their sizes, plus if they are likely to fall out and leave holes. The quality also considers shakes and splits, which determines structural strength. You will find that better quality shed companies pay more for their timber to ensure consistency. This is a long term view as it reduces waste and minimizes customer complaints through poor quality. 

If you want your shed to last then it needs to be treated. That can be either dip treated or pressure treated in a tank, or hand painted by brush. Cheap sheds are often untreated, so the onus is on you to apply treatment before it's assembled. If you don't, the lifespan will be drastically reduced. NOTE: This can be messy and tie you up for space, especially if you need to layout everything on the garden for painting before fitting. Plus you've got the British weather to account for.

Dip treated is usually spirit based, whilst pressure treated is usually organic water based. Painting a colour by brush is also an option as this adds your preferred colour from the outset, but you pay extra for the time taken.

The doors on the lower priced buildings usually only have three timber planks running horizontally on the back of the door. This design has no lateral bracing, and is therefore difficult to keep square.

The minimum you would need to support the door, is 2 x diagonal bracing. One from the bottom to middle bar, and one from the middle to the top bar. This gives pretty good support, but it means that you can only fit a pad bolt on the outside for security.

To install a mortice lock, the door needs to have a frame (for the lock). A fully framed, ledged and braced door is a far superior door, however it takes a lot longer to manufacture and the furniture is much better quality - hence the increase in cost.​

It's much cheaper to have a shed without windows, however if you choose a low price shed with a window, it is likely to be a hole in the cladding with a perspex sheet. This is because glass is more vulnerable and easy to break in transit, especially if it's a supply only shed. Perspex however goes cloudy pretty soon after installation from the Sun's rays. 

Opening windows are much more expensive, as they need a frame and a sash to allow the opening part to work. They will usually come with single glazed glass, which is fitted by the installers. They also take responsibility, so a broken pane of glass would simply be replaced. 

Most shed windows are wooden due to cost, especially as PVC windows are double glazed.​

The style of garden shed is really down to personal taste. Apex roof designs are a traditional style and sit comfortably in a cottage garden surrounded by foliage and colour.  

Pent roof sheds attract those looking for a modern design, as they sit well in landscape gardens that are neat & tidy. In terms of construction, there's not much difference, as they will all use the same materials for the various parts - such as floors, walls, doors, windows and roof construction. 

There's no advantage for one design over the other unless it is obvious in your individual location. And because you can have doors and windows in any elevation, it comes down to what appeals most to you.  

The apex roof has an A frame above the wall sections, and creates the highest point of the building over the middle. This is most useful for taller people, or for storing something tall like a fridge freezer or cabinet. The apex is also a more traditional look, and is popular in cottage gardens. It is preferred to a flat roof shed because the rainwater runs off a sharper roof angle and away from the building. A good tip is to have guttering to the fence side as this gives long term protection to both the fence and the side of the building. No down sides if you like the traditional look of the Apex shed.

The Pent roof slopes from front to back (or back to front if that helps). This means that the front is as tall as the middle of the apex shed, but the back is quite a bit lower (height of the side walls). The other factor is that the rainwater goes off the back - but as it's not a flat roof, there is no stigma attached anymore. If it's tight to a fence, we would suggest guttering to increase it's lifespan of the shed and the fence too! Honestly - the difference between the two designs is how it looks. So the question really comes down to, which one to you like the look of best? Whichever it is, go for that one.

In summary; - If you are looking for a cheap shed, then choose it on price via the internet, and expect it to last a couple years (providing you put it together correctly). 

If you want a mid range product to last at least 10 years, choose one that has been treated or painted, and is constructed using Scandinavian redwood. Items such as framed doors, guttering and roofing upgrades will increase longevity. Oh... and make sure it's installed by the professionals. 

If money's no object then search for Posh Sheds and choose cedar cladding with Tapco slate or a cedar shingle roof.