This is a very common question that many buyers are concerned about. You've found a property you love, but are worried the survey will find some issues which will be too much to take on.
A surveyor does not give a "fail" or a "pass" to a property. The surveyor simply explains any issues which they could identify at the property. Although they give their opinion on "suitability to purchase", this is simply an opinion. If you are buying a property you know will need significant work, you may be willing to take on the work required to make it suitable.
So really a "fail" is different for each situation and buyer.
What issues cause buyers to pull out of sales?
In about 1 in 20 surveys, a surveyor will identify a serious structural issue that needs either immediate attention or further investigation. This could be a crack that poses a risk to the structure of the property, a serious issue with the roof which indicates a new roof, roof structure might be required, or signs of damage indicating there may be high levels of pyrite in the foundation backfill or mica in the blocks.
A large number of smaller issues
Most second-hand properties will have a couple of dozen minor issues. These might range from broken door handles to poor levels of attic insulation. It's part and parcel of buying a second-hand property.
However, if a buyer is looking for a property that they can just move into and not need to do any work to, the number of issues, although normal for an older property may simply be more than they are willing to take on.
Another buyer may be more than happy to continue to buy with the same issues.
If the property has been extended, converted or if it has had porches etc. added, that work would require a certificate of planning compliance or a certificate of exemption. This should be provided by the vendor. If the surveyor identifies any changes to the property, they will include their opinion of whether or not the work requires a certificate. of compliance or exemption in the written report.
When the solicitor follows up on this with the vendor's solicitor, occasionally the vendor is unwilling/unable to provide these. When this happens, your solicitor will outline the risks of buying a property without the correct planning documentation. This risk is enough to cause some buyers to pull out.
A "Fail" is different for everyone!
Every person is willing to take on a different range of known issues. The purpose of a pre-purchase survey is to give you a professional opinion on the overall condition of the property. The decision to proceed or not will ultimately be yours to make!