Getting It Right: Drywall and Fire Compartmentation Surveys
Imagine this: You are talking to an installer on an issue you’re concerned about, and they dismissively say, “I have been doing this for 30 years”. Or more worrying is, “I was shown this way and I have always done it this way”.
Now imagine how many buildings and projects they have worked on doing it the same way for over their 30 years’ worth of experience, without making any consideration for changes in industry standards and technological improvements.
Throughout the year, I carry out a lot of inspections and fire compartmentation surveys on new and existing buildings for a range of uses and a variety of clients. It astounds me that installers still struggle to get the basics right, even now when we can search instructions for correct installation on our mobile phones.
The things I have found in some of the buildings do scare me, and I encounter them regularly. Let’s give you a few examples, starting with some simple ones.
Fixing centres for screws on ceilings and walls.
Manufacturers don’t pick measurements out of thin air; they conduct tests to find the best performance in acoustics and fire. Too many can be detrimental as can be too few. Generally, I tend to find too few.
On a partition, typically the screws should be at 300mm centres max and reduced to 200mm on external corners and around openings. The manufacturers even put marks down the centre of the board to help with the 300mm centres.
Ceilings are different as the boards are laid the opposite direction to the joists or supports/furring system. In most instances the fixings should be at 230mm centres in the field of the board (that means the middle), and then at board ends (they are the cut ends where the gypsum is exposed) the screws are reduced to 150mm centres, and it’s the same round the whole perimeter of the room or ceiling. As there are some slightly different systems, I encourage you to check the manufacturer’s installation details.
Let’s now turn it up a notch, with deflection heads and the use of fixing strap (flat plate) in general.
The flat strap is used on horizontal joints on partitions. This goes between the stud and board on a single layer. On a double layer it can go between the two boards. Its purpose is to maintain the 300mm fixing centres for screws, as before this is how they are tested so it is a critical part of the partition. If it’s not there, the manufacturer will not warranty the partition and it will not perform as required.
The same goes for deflection heads, they have been designed and tested to perform and serve a purpose. They allow a floor structure to move due to loads (dead or live) and typically is an up and/or down movement. What I see from time to time are studs screwed or crimped into the head track! Will that allow any movement? Frustrating, but not as much as when the boards screw the boards into the head track, which raises the same questions.
The other point I wanted to raise about flat strap is it is also used in a deflection head to maintain the 300mm centres as you should not fix into the head track like normal. This should sit a set distance below the bottom edge of the head track with is normally the defined distance of deflection. As above, this is to maintain the 300mm centres for screws, but if this is missed, what happens in a fire is the top of the partition opens and allows the fire into the partition cavity/core quicker, and again causing it to fail prematurely.
The final and most worrying issue are partitions of compartment lines that are required to achieve a fire rating but have only been boarded on one side!
As mentioned, these are required to achieve a fire rating in both directions. Compartment lines boarded only on one side is not something you will find in any manufacturer’s literature, which means it will not work. This has been found on risers and onto the back of bathroom pods, where individuals believe that the bathroom pod will give a fire performance, so it does not need boarding. Now bathroom pods are made from GRP (Glass Reinforced Plastic) and we know what happens to plastic when it gets hot or next to an ignition source? It either melts and goes soft, letting off flammable gases, or it catches fire and burns really well, which is not good when people believe it will stop a fire.
So this is my first blog of many we hope, where we want to support you and offer hints and advice. Please contact us and we will be happy to arrange a visit to investigate any suspicions or concerns you may have, or answer any questions.
This is the first in our series of Director’s Dispatch blog posts where our Technical Director shares information, tips, and advice pertaining to Fire Safety issues and best practices. Our Technical Director has had 20 years experience as a qualified plasterer and dryliner, with 10 of those years teaching in an Academy run by one of the UK’s largest manufacturers where he was also Technical and Training Manager. Over the years he has trained site managers working for Tier 1 contractors and house builders, and ran courses on installation of stud partitions, MF ceilings, plastering, jointing, and others. His training videos for the academy are still in use.