Recessed lighting in ceilings to intermediate floors
18 February 2020
Neither the NHBC Standards nor the requirements of the Building Regulations for floors to achieve a satisfactory fire resistance have changed in recent times but we are aware that builders and developers need more guidance in this area.
Please read on to make sure you’re aware of your responsibilities in this area and what your Inspector will need to see before being able to sign off your site/plots for warranty and/or Building Control.
Regulation B3 - Internal fire spread (structure)
B3 states as follows:
(1) The building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period.
(2) A wall common to two or more buildings shall be designed and constructed so that it adequately resists the spread of fire between those buildings. For the purposes of this sub-paragraph a house in a terrace and a semi-detached house are each to be treated as a separate building.
(3) Where reasonably necessary to inhibit the spread of fire within the building, measures shall be taken, to an extent appropriate to the size and intended use of the building, comprising either or both of the following—
(a) sub-division of the building with fire-resisting construction.
(b) installation of suitable automatic fire suppression systems.
(4) The building shall be designed and constructed so that the unseen spread of fire and smoke within concealed spaces in its structure and fabric is inhibited.
Approved Document B Volume 1 - Dwelling houses gives further guidance:
Section 4, loadbearing elements of structure points towards to appendix A which states that:
- For floors in an upper storey of a 2-storey house (but not over a garage or basement) should achieve modified 30 minutes fire resistance.
This being: 30 minutes loadbearing capacity, 15 minutes integrity, 15 minutes insulation.
- For all other floors a full 30 minutes is required
There is no specific test for a recessed downlighter and so they must be tested as part of an overall floor construction. The whole floor is subject to the test including any elements that are to be part of that floor construction which include any recessed light fittings.
Fire hoods are subject to a different test and are only required to be tested within a plasterboard construction.
Extended Application Assessments
It is impossible to test every combination of floor and recessed light fitting, therefore it is acceptable for a manufacturer or builder to have an Assessment in Lieu of Test (AILOT) written to either prove a specific configuration that has not been tested or to extend the application of tests which have been done.
The assessment must be prepared by an organisation that has the ‘necessary expertise’ as defined in paragraph B5 of ADBv1/2. This states that tests and assessments should be carried out by organisations with the necessary expertise. For example, organisations listed as ‘notified bodies’ in accordance with the European Construction Products Regulation or laboratories accredited by the United Kingdom Accreditation Service (UKAS).
Ideally the assessment should be undertaken by the laboratory that undertook the original test but if not it will be necessary to ensure that the body undertaking the assessment is suitably experienced to do so.
Assessments must be based on relevant test data and details of the tests used to support the assessment will need to be included within the assessment report.
Timber engineered and metal web joists
Test information will refer to one type of joist, but it is also acceptable to NHBC Building Control to use the test to demonstrate compliance for other engineered joist floors where the key elements of the test are the same or better. These elements would include:
- Joist type i.e. engineered joist or metal web
- Joist size including the central web thickness and grade of board
- Spacing of joist
- Thickness of plasterboard
- Density of downlighters
In addition, we would need to ascertain that the downlighters installed are the actual model that has been used in the test.
Fire Rated Hoods
An alternative approach to the use of fire rated downlighters is to use a suitable fire-resistant hood. The hood must be suitable for the type of downlighter being fitted and have been tested to achieve the required fire resistance of the ceiling construction. They should be installed in accordance with the manufacturer’s instructions and test criteria using the same thickness of plasterboard. In this scenario, the joist type is not relevant as long as the ceiling construction complies. It should be noted that there are fire hoods available that can be fitted retrospectively via the downlighter aperture.
Working with industry
We are engaged with technical bodies such as EWF and LIA along with a number of manufacturers of downlighters and joists, encouraging them to work together to produce information that is of benefit to our customers and the industry as a whole.
Need more information?
Please contact your appointed Building Control Surveyor in the first instance.
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