U-value Calculator
We provide U-value calculations free-of-charge to show compliance with current Building Regulations, Standards and best practices.
Page updated 12/02/2026
Most building work being carried out in Northern Ireland must comply with the Building Regulations. Part E of the Building Regulations states the following for external fire spread:
36. The external walls and roof of a building shall be so designed and constructed that they afford adequate resistance to the spread of fire over them, and from one building to another, having regard to -
a) in the case of an external wall - the use, position and height of the building; and
b) in the case of a roof - the use and position of the building.
Note that complying with the guidance in Technical Booklet E does not guarantee that building work complies with the requirements of the regulations. There may also be other ways to comply with the requirements than those described in Technical Booklet E.
