Intumescent strip fitting to fire doors.

Discussion in 'Carpenters' Talk' started by gullrock, Feb 18, 2006.

  1. gullrock

    gullrock New Member

    I need to replace my old apartment front doors (which are currently covered in asbestos on the inside!)

    The doors open off from an internal landing so I am proposing to fit fire doors with an Intumescent strip.

    I understand that I need to rebate the sides and top of the doors to sink in the strip but what do I do about the bottom of the door?

    The door frames are slightly awkward sizes so I may need to plane a bit off all sides, is this likely to be a problem. With regard to the fitting of yale type locks as these are usually fairly high up, what about finding a good fixing because cheap internal doors don't have anywhere to do this except for where the handle goes? Advice on type of door would be helpful.

    Finally, would it defeat the object of a fire door to fit a letter box?

    Any advice on the most cost effective way of doing this would be greatly appreciated.
  2. Scrit*

    Scrit* New Member

    Is the requirement for 30 minute or 60 minute doors? The advice I've had from the local fire inspectors is that 30 minute doors require a single intumescent strip which is grooved (not rebated) into the edge of the door whilst 60 minutes require both an intumescent strip and a brush-type smoke seal (again grooved). If you were putting-in a new door/frame set these would ideally go into the frame rather than the door, but retrofitting an existing frame would be an absolute nightmare. The seals should go round all 4 sides if possible by installing a threshold on the floor beneath the door is necessary, although a close-fitting brush type seal may meet the requirements, too. The TRADA recommendation is to use narrow leaf steel hinges (3 on 1 hour doors) so that the intumescent strip is continuous, use slim locks painted with white intumescent paint or paste and to avoid over mortising or cutting through the door because if you do you'll destroy it's fire integrity. So letterboxes are a no-no. Most fire doors are either solid core or mineral infill normally with solid wood lippings, so you shouldn't experience the voiding you'd get with cheap internal doors, however fire doors do come with a fire certification sticker attached and the amount of resizing you can carry-out on fire doors is very limited. As you are in a shared occupancy building have the insurers or fire brigade imposed any conditions on the building such as insistance on 1 hour doors? It might be best to check this.

    Maybe this document from the UK Fire Safety Advice Centre would help

  3. inkpad

    inkpad New Member

    You should fit a smokeseal (brush strip) with the intumescent strip. The smokeseal is required to flat entrance doors regardless of 30min or 60min.

    You can get combined intumescent smokeseal strips

    The smoke seal is to stop any smoke from your flat leaking into the lobby/corridor area and blocking everyone elses escape (and vice versa - any smoke in the lobby leaking into you flat while you wait for the fire brigade to rescue you - if the lobby/corridor is affected by fire)

    You can get intumescent letter boxes - check with the firedoor manufacturer that the door is ok to be modified and still be FD30S (or higher if needed)

    Envirograf do a range of fire products like letter boxes, intumescent strips and inserts for around and below locks/hinges etc

    3 hinges to any fire door is needed - normally stainless steel - not brass due to melting temp

    obviously a selfcloser needed
  4. gullrock

    gullrock New Member

    Firstly thanks for the advice.

    I have not been required to do anything but wish to replace the doors as they are old and thought it would be a good idea to replace them with an acceptable fire door in order to meet any future requirements. I did think that 30 min was acceptable though???

    The web site looks helpful so no letter boxes is ok but I am still at a bit of a loss as to narrow leaf steel hinges - how big they are what they look like and where to find them!
  5. bigjules

    bigjules New Member

    If you are fitting new doors, ask the supplier for a copy of the manufacturers fire test certificate - this will show, in detail, what ironmongery, intumescent strips and frame the door was fitted with when tested.
    You should not fit any ironmongery of a lower specification that that tested.
    Hinges DO NOT have to be stainless steel but they must be CE (European standard) certificated and marked.
    Letter plates can be fitted provided that they have an equal fire rating to the door.
    Intumescent strips can be fitted to either door or frame.
    As far as I am aware, 30-minute rating is sufficient in a residential situation.
    In all case, refer to the manufacturers fire test certificate.
  6. bigjules

    bigjules New Member

    One more point - you can get intumescent pads that are fitted behind the hinge leafs rather than using narrow butts, there-by providing a continuous strip.
    I don't believe that intumescent has to be fitted to the threshold - stiles and head will comply but as stated, check the fire test certificate.
  7. gullrock

    gullrock New Member

    I liked the idea of "you can get intumescent pads that are fitted behind the hinge leafs rather than using narrow butts," but I am unclear what you mean by behind the hinge leafs. To my simple mind do you mean that they fit on the small amount of timber left on the door that has not been rebated for the hinge?

    It sounds as though it may well be safer to fit a strip also into the base of the door. Do you know how much do they actually expand when heated?
  8. chanlee

    chanlee New Member

    the strips will expand between 0-6mm, depending on the temperature subjected to. There isnt much point fitting them on the bottom as they need a considerable amount of heat to expand. In a fire, floor temperature doesnt rise much.
  9. gullrock

    gullrock New Member

    Thanks for all the info everyone!

    I have also been on to the fire brigade safety team and they confirm that there is no need to put anything at the bottom of the door as there no real problem with smoke coming in through the base of the door. They do state that the maximum gap should be < 8mm and that there should be some form of threshold so that no floor coverings bridge between the rooms either.

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