At the moment in the City of Bristol, UK, there is an increase in people wanting to either:
A) Convert a loft
B) Convert a basement
1/ Do they follow building regulations?
Any builders you work with in Bristol, or anywhere else in the UK for that matter, should be adhering fully to British building regulations.
These are designed to ensure that building practices carried out by building professionals are safe, that the construction being developed will stand the test of time, and also that the structure itself (as a finished product is both legal, and reliably built).
Here is some information about building regulations for loft conversion: https://www.planningportal.co.uk/info/200130/common_projects/36/loft_conversion
Regards building regulations for basement conversions, much of the same applies, here is a resource for basement conversion building regulation: http://www.northampton.gov.uk/info/200011/building-control/1703/building-control-guidance—basement-conversions
It is important to check with the builders before commencement of the project that they adhere to building controls and regulations.
2/ Do they have the right accreditations?
All builders, especially ones working on loft conversion and basement conversion should hold a CSCS card, this means that they have qualifications necessary for them to be working as construction professionals.
Check also that any professionals working on plumbing or heating are gas safe certified.
3/ Discuss Pricing Before hand
It is very important that all parties involved in a home conversion are clear on the pricing, it is best to avoid confusion later as basements and lofts can become highly expensive projects, to avoid nasty surprises it’s best to clarify with the company you are working with.
4/ Plan a payment schedule with the building firm
The more organisation the better, this is why setting a payment schedule is a good option, this avoids possible disputes and confusion relating to payment dates, and should a situation change, fluid upfront communication with the builder would undoubtedly be appreciated.
5/ Clarity of communication
You can only be clear on matters of planning, turnaround times, and payment plans with clear, honest communication with the building company you choose for the work.
Keep that open line of communication at all stages of the project.
Adhering to the above points should as much as possible ensure that you have the best possible experience when converting your loft or basement in the city of Bristol.