Lifespan of intumescent fire paints/varnishes

[Ricardo]

With regards to upgrading fire doors with intumescent stains etc , can anyone enlighten me as to whether or not such  products have a life span once applied, or is the product likely to last forever or does it lose its fire resisting properties after a certain timescale, and need reapplying. I guess I should contact the variouys manufacturers and ask them directly, but would welcome any views of the forum as well.

[Ricardo]

On speaking to a couple of companies about their products I am told from one that their product should be reapplied between 5-7 years after initial appplication, the other has said their product once applied can last for the life of the door, provided there is no damage to the door. I will continue my research and report back any more findings.

[kurnal]

Hi Ricardo
I guess this is going to be down to each individual manufacturer.Its an interesting point  especially because  the BS476 is a one off test that has no regard for longevity and durability - bit like the car MOT.

I was once told on one presentation - I think on a visit to the Sealmaster test facility -  that "the more common sodium silicate based intumescent strips are encased in plastic as they are hygroscopic and the ends of the tubes should be sealed when cut otherwise the performance will decline". I really dont know how valid this is- but I bet somebody on here does.

[Ricardo]

Thanks for the feedback kurnal, you never cease to amaze me with your absolute  extraordinary knowledge of fire safety matters, hygroscopic is a new word in my vocabulary now.

What I have been finding out in my discussions with manufactures of intumescent products for upgrading existing panelled doors so far is that their products need different thicknesses of door panels to be effective once applied, and strict following of their application instructions to provide a 30 minute integrity, so far I have been told this ranges from 6mm to 12mm thick panels, they can provide me with test evidence, and confirmation that their products comply with the tests contained in BS 476 -22 ( thats what i am being told)

I have also been told by one that a 1mm intumescent paper, veneer or panel, once activated, expands to twenty times its original size, but the panel must be at least 6mm thick to begin with to achieve 30 minutes.

I have managed to get my hands on the book by ASDMA you suggested, I never knew there was so much that could be written about doors.

[John@EPL]

Just a thought. Have you checked with your council for your application. My local council won't accept anything but fire doors for fire door purposes. We have removed some very thick and heavy doors that would take hours to burn through and replaced them with 30 min fire doors made from two sheets of 6mm ply and some 2*1 ( but had a conformity sticker on it).
You can get some good hotel quality panel fire doors from Howdens these days for about £50.

[kurnal]

John I wonder if your local council has a listed buildings officer? There may be irresistable forces and immovable objects you could bring together, always entertaining. Thanks for the info on Howdens- will look for a web site.

At Sir Richard Arkwrights original cotton spinning mill- the birthplace of the industrial revolution and now a world heritage site we had to find a solution to satisfy the listed buildings officer where we wanted to protect a six storey staircase and the listed buildings officer insisted on retaining  25mm thick panel doors with huge holes in the meeting stiles caused by many years of abuse by pushing barrows through them.  Even the holes were protected! We arranged for them to be infilled by letting in new wood which was left undecorated, and the whole treated to proprietary intumescent varnish and paint, the result accepted by all as a step in the right direction.

Working on another place at the moment with beautiful mahogany panel doors with 50mm stiles and rails and 28mm thick raised and fielded panels, using an envirograf varnish, surface mount seals and  concealed self closers (the ones we dont normally like) on these. To remove the doors would be a crime.

Just an observation on some of the test data available for proprietary treatments- often they are not a test certificate as such because the manufacturers tend to make up a composite panel of different materials, thicknesses and with different treatments, to maximise the benefit of the very expensive fire tests. The test will run as long as possible, recording the times that individual elements fail.(NB although this may be run for longer than 30minutes, the products are only sold as suitable for 30 minutes applications)  Fair game in my view but I can understand some enforcers being nervous about it because it is very often not tested as a doorset, and the first point of failure is  usually around the periphery.

[lambie]

If doors are coated with intumescent treatments which have certification to show conformity and are subsequently painted over with oil based products do they then lose their integrity? Considering intumescent strips maintain theirs after a few coats of similar paints.

[redbadge]

The essential point is the evidence generated for the paint / lacquer when it was tested it was tested on a specific substrate which will be disclosed in a test report to either BS476 part 22 or BS EN1634 part1. Deviation from this (tested substrate)will only be possible where a test programme on varying substrates (materials / thicknesses etc.) has been conducted an enable an engineering assessment to be produced in line with the requirements of BS ISO/TR 12470: 1998.

E.g. if the product is only tested (succesfully) on a hardwood (of a stated density) substrate 25mm thick then this is all it approved to be used on, however if it had been tested on a softwood substrate 18mm thick and a hardwood 25mm thick then extrapolation / interpolation would enable a hardwood 18mm thick to be approved, and also permit less dense hardwoods to be approved down to the density of the softwood. The graeter the range of the testing then the more applications would be proven.

As a further note, where damaged timbers are replaced the method of bonding is as equally important as the material used for the repair - no point in sticking chunks of timber in with thermosoftening adhesive e.g. pva unless this is specifically proven to work by test.

Intumescent seals are tolerent of overpainting as they are encased in pvc (usually) which isolates the material from overpainting. Specific guidance regarding overpainting lacquers etc should be sought from the manufacturer, although it would seem sensible to overpaint with further coats of intumescent lacquer rather than something else?

[lambie]

Thanks Redbadge, most useful.  The doors had been overpainted by some who did not know better. I came too late to urge caution.

[Ricardo]

Thanks Redbadge, most useful.

Now Lambie, if you understand all that you are a genious, can you please expalin to me in plain English what that all means.

[redbadge]

Thanks Redbadge, most useful.

Now Lambie, if you understand all that you are a genious, can you please expalin to me in plain English what that all means.

Hopefully of use...

The approval for the product can only relate to specific replication of what has been tested or has been approved in a fire engineering assessment - just because coating A has been tested on substrate Z it doesn't necessarily follow that it will work equally on substrate Y
?