Routing intumescent strip fire door

[Gary111]

Hi, I've just got a router and intumescent cutter to add intumescent strip to a fire door.
Had a test run on some MDF, it was ok, just seemed like I was wobbling slightly off square on the edge of the MDF.

Wondering if there are any other guides I should be using, or do I just need to practice more.
Obvs the fire door will be thicker so should be easier because of that
.
Thanks

 

[Deleted member 174758]

I presume that you have the type of cutter which has a guide bearing at the top or bottom.

In which case the bearing needs a reasonable amount of surface to run against, such as the edge of a 35mm (or thicker) door.

Before starting you will need a couple of trestles to support the door, flat, and you will need to remove the hinges, door closer, any kick or finger plates and any handles, spindles, lock escutcheons, etc on the face of the door on which the router will run.

If you are doing this task with a straight cutter and a fence you ideally need to install longer than normal fence rods (often possible to use just silver steel rid in either 8 or 10mm diameter) and two fences (I.e. an extra one, so one each side of the router base plate) on your router (although one of the fences can be home made)

Images courtesy of Trend Knowledge Base - please see the Trend Machinery UK site for further articles on intumescent strip groove cutting. Please note: I have no association with Trend orher than being a normal, paying customer

 

[Gary111]

Thanks maybe I'm overthinking this but at the corners where the 2 seals meet, should I mitre them so that they stick out slightly at the corners, if I cut them straight it seems there will be a tiny gap at the corners ?

 

[^woody^]

Envirograf 'Product 78' does not need rebating.

 

[Deleted member 174758]

Square cut, make the top piece fit inside the two pieces that run up the sides (aesthetically more pleasing?). We generally use tin snips to cut intumescent seals as it can be pretty dangerous trying to do it with scussors or a Stanley knife. If you think about it you are going to have breaks (gaps) where the lock and hinges are in any case (which is why there are intumescent pads made to fit beneath hinges and why on 1 and 2 hour doors we end up wrapping locks in Intergraf lintumescent paper and using intumescent caulk all over the place), plus no seal at all across the bottom of the door in many cases.

The brush strip is a cold smoke seal, which is designed to limit the ability of smoke to pass through the door opening and give anyone in the room a greater chance to either escape, or await rescue without suffering the effects of smoke inhalation so much.

In the event of a fire the intumescent material eventually swells to close the gaps between the door and the frame/casing but by that point the temperature is so high that you'd be dead in all probability, but the seal around with the door does prevent the fire from spreading outwards for 30, 60 or 120 minutes respectively depending on the type of door and casing set installed, and stopping the spread of fires from one compartment of a building to the next gives extra time to both evacuate the premises and for the fire brigade to bring it under control

 

[Deleted member 174758]

Envirograf 'Product 78' does not need rebating.

Standard intumescent strips don't fit in rebates, they sit in grooves, Woody, not the same thing.

The product you refer to (Envirograf 78) can be awkward to get a decent seal on old door casings with and is generally more of a faff to use with door closers (I've used a lot of Envirograf stuff on listed building jobs)

 

[Gary111]

Ok thanks very mu h for your help jobandknock