1/ The floor is absolutely crucial to the lastability of garden sheds and garden building so it is important to ensure that it is not made from chipboard or OSB (sterling or wafer board) board as these are not really suitable for outdoor use where there is a chance they will get wet. Chipboard is by its name made from wood chips, OSB is wood shavings stuck together - which is fine for kitchen and bedroom cabinets covered in melamine - but it is NO USE whatsoever in a shed. On some of the floors on these cheap sheds the floor is only 10mm thick (thin!!) which is only about 3/8 of one inch - smaller than a standard pencil.
Also notice that most companies offering chipboard or OSB boards describe them as solid sheet materials as they are too embarrassed to tell you what you are really getting and they normally exclude the roof from any warranty over the minimum period as they KNOW these boards won't last (Ask them the question)
2/ The other important consideration is the thickness of the floor joists, which can be as small as 28x28mm (1" x 1") on these cheap sheds, and the spacing of the floor joists. On the cheap sheds you will find the gaps in between quite large and with the thin chipboard or OSB board won't stand up to much heavy use. You will find that the boards start sagging and eventually will break, certainly if there is any damp coming up from the ground.
All our floors are supplied ready made, no assembled to do. All our floors are made from solid T&G timber boards with heavy duty floor joists, we do NOT use chipboard or OSB board as they are NOT suitable for outdoors use. On the Diamond we do use timber T&G boards on the floor, except if the floor is 8x8 and over where we use the superb moisture resistant Caber board, grade v313. This is similar to what is used in a brand new house in a kitchen and bathroom where there is a possibility it could get wet so is ideal.
We are confident in this because we owned and ran one of Surrey's largest company supplying garden sheds direct from 1979 (pre Maggie Thatcher) for over 20 years.
We have been involved in garden sheds and buildings for over 35 years. We know if the shed is put onto a dry base and that the building is treated every year with a water repellent preservative and that the roofing felt is kept in good condition then your new garden building will last for a very long time. Most of the sheds we built back in the early 80's are still going strong.
Further articles about garden sheds, workshops and the type of timber cladding you should use to follow. Also about the truth behind so called 10 year guarantees