Fire Rated Packer – Pk 100

A fire rated packer does one job, and it needs to do it without becoming the weak link in a fire-resistant installation. These 15x100mm strips are sold in packs of 100 and come in three thicknesses: 1mm green, 3mm white and 5mm blue. Colour coding is the sensible bit. Nobody wants to be on their knees at a door frame, holding a feeler gauge in one hand and a cup of tea in the other.

If you fit fire doors, frames, linings or fire-stopped partitions, you already know that a wonky frame is not just an annoyance. It can compromise the whole assembly. Packers let you set a frame plumb and square, hold a consistent gap, and take up the small irregularities that every opening seems to have. A fire rated packer is made for exactly that, so you are not stuffing offcuts of whatever was lying about behind a frame that is supposed to hold back a fire.

Where Fire Rated Packers Get Used

The main job is behind and around fire door frames, where the frame sits against a masonry or stud opening that is never quite true. Pop a packer in at each fixing point, check your plumb and your reveals, then fix through. Same thinking applies to door linings, architraves, and anywhere you need to hold a small gap open or take out a bit of play in a fire-rated build-up.

The three thicknesses cover most of what turns up on a typical job. The 1mm green is for fine adjustments and for stacking up to a precise dimension. The 3mm white is the general workhorse. The 5mm blue handles the bigger gaps where you would otherwise be reaching for something chunkier. You can combine them too, which is handy when the opening is somewhere between sizes and never agrees with the drawings.

Choosing the Right Thickness

Measure the gap at each fixing position, not just once at the middle of the frame. Openings drift, and a gap that is 3mm at the top can be 6mm at the bottom. Build up with the fewest packers you can to reach the dimension. Fewer layers means a tighter, more stable fixing and less to go wrong.

At 100 per pack, there is enough here for a decent run of doors, and the price per packer is low enough that nobody is tempted to improvise. Buying a few packs across the thicknesses and keeping them in the van saves a lot of last minute faffing when the frame turns out to be out by 4mm on a Friday afternoon.

These are a trade product for people who care about compliance and about getting the job signed off first time. Fit them as intended, keep the build-up sensible, and follow the door or frame manufacturer’s instructions for fixing centres. A fire rated packer is cheap insurance against the kind of snag that holds up a handover.