downlights and joist

[james king]

hi all i know there are maunfacuer distances but how many of u actully go as close to joinst as possible. i have never heard of a joist catching fire befor. any one put one touching a joist ?

 

[Amp David]

Most fittings give a safe distance of 50mm distance from any joist etc dont they.

 

[David Styles]

I had a customer quote me some of the comments on this website today so I thought I'd post his topics with my answers...

Fire rated downlights: standard fire rated downlights are not designed for installation into spaces without ventilation. Equally they are not designed to be installed somewhere really hot i.e. in fireproof boards above a working fireplace. If you use a fire rated downlight in these places it will suffer from (at least) premature lamp failure and (at most) breakdown of components i.e wiring and potential fire. There are some specific products that are designed for use under or in insulation these have heat sink to dissipate heat.

Cutting joists: only cut a joist if the integrity of the ceiling structure is maintained or repaired. Chopping out chunks to suit poor planning is a mistake and poor workmanship. We all get it wrong sometimes - professionals make good any damage at the time.

Locating fixture next to a joists: F mark testing considers the temperature of the bezel at the point the fixture is held in the ceiling. The temperature in other places can be a lot higher i.e. the pinch of a lamp (at the top by the pins). If you decide to fix light fixtures close to any combustible material above the ceiling consider carefully the lamp wattage and heat generated in the space and factor in the depth of the void and the spacing of the joists. Clearly LED lamps are always going to be better as they generate the least heat. NB Using a fire rated downlight will make very little difference to this type of installation - although the versions with heat sink will greatly reduce the heat build-up.

Insulation: pushing blanket insulation in a ceiling void is a waste of time. It moves back to its natural position very quickly and will cause your light fixture to overheat and fail. Pull out any loose insulation to make the required ventilation space.