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Punctured Flat


Suspended ceilings make an essential contribution to the acoustic performance of separating floors by isolating (or shielding) the floor structure from the flat below.

If the ceiling is punctured to install services, then sound could get into the ceiling void, and the isolation is lost.

Recessed Lighting

However, (and without getting too technical about wavelengths and diffraction) the ceiling can tolerate holes cut for recessed lighting, provided they are maximum 100mm across; and no more than one per 2m2 of ceiling in the room affected. Therefore, for most robustdetails® floors, a 10m2 room can be fitted with up to five recessed light fittings. If you need to install a greater number, or larger size of lights, then there’s no problem as long as you ensure the fittings have been tested to our Appendix F. If you’re planning to install recessed light fittings in a lightweight floor (timber or steel) then they must always be tested and approved as set out in Appendix F, irrespective of number per square metre or size.

Extract Fans

Extract fans can also be accommodated, but with these, the aperture has to be fully sealed to the duct to prevent air paths into the ceiling void; and the duct must not create a rigid connection of the ceiling lining to the floor structure. Other issues such as fire, and the environmental noise of the fan operating, will also need to be considered.

Any ductwork exiting the ceiling must be fully boxed-in using gypsum board to the same specification as that used for the ceiling.


Inspection Hatches

A number of services can be run above the ceiling; and if this includes a gas flue, you may need to think about fitting inspection hatches.

If this is the case, then ensure the hatch is acoustically rated to be at least as good as the gypsum board that it is replacing.

Best Advice

If number or size of apertures is larger than described above, then we would recommend installing a secondary ceiling to take the fittings. This will ensure the primary ceiling remains intact. The secondary ceiling should be hung from the metal frame or resilient bars, and not from the structural floor, so check that these components can accommodate the extra weight.

As ever, the Technical team are available to answer your questions on this and any other Robust Detail matters.

If you have any techncial enquiries please do not hesitate to contact our technical team on 03300 882140 or email:

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