1/ Some companies offer 10 year Warranties or Anti-Rot guarantees, HOWEVER, these come with very strict conditions in so much as your new shed has to be re-treated as soon as it arrives. You also have to ensure that is it re-treated every single year afterwards. How you prove that I don't know. The warranty will be void if you put in on any base where damp could get to it and if any of your shed is touching another building this would also void any warranty.
2/ Most of these cheap sheds also do not cover the sheet (chipboard or OSB board) material floor and roofs, both of which are crucial for the lastablilty of your shed.
3/ It is vital that any guarantees offered are offered by companies which have been trading for a long time, otherwise, you may find, if you need to claim - and you have fulfilled all the terms and conditions - that they are no longer trading.
We at 1st Choice, are very happy to match any guarantees, subject to the same conditions from the cheap shed companies. 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 far longer than 10 years. Most of the sheds we built back in the early 80's are still going strong.
All our timber buildings are made in the UK so you can be sure you are helping the British economy and helping to keep people in work.
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