There can’t possibly be anything that technical about a simple plasterboard ceiling – can there? Well, the answer is yes, says Steve Halcrow, if you’re doing it properly!One of the things that can come with time and experience, if we are not on our guard, is complacency. This is especially true if we are dealing with something that is familiar to us, which we do frequently, and in my experience from the various technical visits I undertake I see evidence of this being the case in the construction of just such things as suspended ceilings.
It is true that, provided the right guidelines are followed, there is little in the construction of a typical MF ceiling (or indeed a typical lay-in grid ceiling) that should challenge us unduly. I am afraid to say though that all too often such guidelines are not observed closely because it all seems too simple. After all, it’s only a ceiling!
Some of the most common errors and omissions I witness include:
- incorrect spacing of primary and/or secondary channels
- incorrect spacing of hangers
- wrong type of fixings used
- insufficient number of fixings used
- inadequate allowance made for fixtures and fittings.
It really is vital to check items like these because any one of these can compromise the strength and integrity of the overall construction, and a combination of two or more could be catastrophic.
The answers are usually readily available through the manufacturer of the ceiling in question, so the key is making sure you ask the right questions. Beware the trap of saying “we’ve built these before so we’ll do it the same way again,” without first making sure you’ve asked some of the fundamental questions, such as:
- What is the soffit to which I am fixing? Can it take the type of fixing I need to use?
- What loading will be applied? Make sure you account for all boards, light fittings, etc. as far as possible, to ensure you get the grid and hanger spacings right
- Is there a fire rating? Do not assume that a board or combination of boards which achieve a given fire rating on a partition will do so on a ceiling; often they won’t.
- Is there any acoustic consideration? If so, does it mean switching to specialist hangers?
- Do we need to allow for pattressing of any kind to accept fixtures and fittings?
In the case of loadings from fixtures and fittings it is often relevant whether these are mostly evenly spread across the ceiling or apply a ‘point load’ to a concentrated area. Furthermore, with the airtightness controls on buildings now we find that on occasion ceilings are affected; it can be that when internal doors are opened then wind pressures within the building itself can affect ceilings and in some cases make them deflect, producing noises and even cracking joints.
Obviously a key issue is the fixing of the ceiling into the substrate above and it is imperative to get this right. Once again consult the manufacturers’ recommendations very carefully and assume nothing until checked. Once things are ready on site consider having pull-out tests conducted so that you are confident the soffit is going to support the load in question safely. Our counterparts at the AIS have produced a guide to ceiling fixings which you can download from their website at http://www.ais-interiors.org.uk/publications/best-practice-guides/
In short the message is simple: check, double check, and make no assumptions. It is far better to be safe than sorry, even if you think it’s just a simple ceiling.