Steel Beams Fire Encasement

[Mr Punter]

21 minutes ago, juncopartner said:

1 hour, looks like he's correct.

 

I know it is 1 hour.  I thought that having it in the floor zone with the 2 x plasterboard would be acceptable.  Architect wants intumescent paint.

[TonyT]

We have built 2 commercial buildings in the past 10 years,

steels were sprayed with a paint to provide fire protection, only plaster boarded when the adjoining wall was plaster boarded.

 

 

[juncopartner]

21 minutes ago, Mr Punter said:

I know it is 1 hour.  I thought that having it in the floor zone with the 2 x plasterboard would be acceptable.  Architect wants intumescent paint.

Either way as long as it achieves one hour.

[juncopartner]

38 minutes ago, nod said:

Single and two story are fine 

Anything over The beams need 60 minutes protection

Yet again this is incorrect, single storey buildings do not require fire resistance,. 
Two storey buildings of any type most definitely require fire resistance, and this is dependent on their use, height and whether they are sprinklered this can be 30. 60, 90 or 120 minutes.  
In the vast majority of domestic dwelling houses this is 30 minutes, unless a floor level is over 5m in height then one hour applies.

 

[Gus Potter]

Hello all.

 

8 hours ago, Eviljames said:

Hello folks, just wanted to check if steel beams that are fully enclosed within the void between a ceiling and the floor above need to be individually encased with fireboard within the void OR if providing a fully fire rated ceiling below will suffice.

 

Thanks in advance.

 

 

Good points from all. Generally if the steel is within a fully protected enclosure then that alone is often ok, no need to protect the individual beams. This is akin to say enclosing a steel beam within a brickwork pier or thinking laterally, a piece of rebar within a concrete slab.. the concrete cover insulates, the rebar stays coolish, thus the floor stays up..

 

As a general point which I hope will be of help to members.

 

Fire protection of beams etc can be difficult to get your head around, even if you are dealing with it on a fairly regular basis. One starting point is if you can get an understanding of what "Fire Resistance" means. As an aside, the English and Scottish fire regs differ in places but the principles are the same. I'm more familiar with the Scottish regs so to all.. please correct if I misquote the English regs.

 

The overall "fire resistance" of say a plasterboard ceiling / wall or steel beam protection is obtained by combining a number of different properties. One property is called "Insulation" You can see this mentioned in for example the English regs (ER) Approved doc B clause B19. What this property measures is how well the material..be it plaster board or something else insulates what you are trying to protect. Here what you are trying to do is to not just to reduce the "convected heat" but also the "radiated heat" and this is where the "insulation" comes in. We know that say an electric bar fire can set light to your sofa.. by radiating heat.. it's the same principle.

 

You'll also see a property called "integrity" mentioned in clause B19. What you are doing here is making sure that the "insulating" layer is firmly fixed in position such that (in the case of plaster board , fireline board, wall cladding..) the seams don't start opening up. If this happens then sparks, flames and hot gasses bypass the insulating layer and compromise what you are trying to protect.

 

Now knowing this will hopefully help with the next bit. While a single layer of 12.5 plaster board / fire line board etc may give you say 30 minutes (resistance) much depends on what it is fixed to! Say for example you have 50 x 25 mm timbers levelling out the ceiling. In a fire the fixings get pretty hot and the small timbers may not offer the support to maintain the "integrity"

On the other hand if you have fixed your plaster board to big solid joists with good "chunky dwangs (noggins) then your ok. Below is a link to the British Gypsom White book.

https://www.british-gypsum.com/literature/white-book/floors-and-ceilings

 

There is lot's of good info in the white book for example, often worth just a rough peruse.

 

 

A good example of the above is to look at page C6 SO6 P04 Here you can see how you can get your 30 min with their product but the info they give only covers you for certain joist sizes and floor thickness etc.  I have screen shotted part of the page above. The big solid joists etc contribute to the integrity. the plaster board etc to the "insulation" giving the "fire resistance"

 

Fire protection.. It's a big subject but if you can get your head around some of the underlying principles you can be; safe, get a handle on what you may need for your own particular design and maybe save money too!

 

 

 

 

 

 

 

[Gus Potter]

56 minutes ago, juncopartner said:

Yet again this is incorrect, single storey buildings do not require fire resistance,. 
Two storey buildings of any type most definitely require fire resistance, and this is dependent on their use, height and whether they are sprinklered this can be 30. 60, 90 or 120 minutes.  
In the vast majority of domestic dwelling houses this is 30 minutes, unless a floor level is over 5m in height then one hour applies.

 

Just to add a bit.

 

Looking back at the posts everyone makes good points and are "half right" or more in my view. I would list them but suffice to say.. thanks to all. I would like to think that I too am "half right" but probably also more "half wrong"..that is the nature of "fire protection" in some ways.

 

It's also important to look at the buildability / practicality side of things as some generic fire protection details /measures look great on a drawing but can be heavily labour intensive with the associated increase in cost.

 

The devil is in the individual project detail, so for all, the more information you can provide the better as each project is often different.

 

On a positive note.. don't forget that sometimes while you may think that the fire protection costs a lot it can also form part of your acoustic insulation. From memory I think PeterW has posted about this as have many others. Worth trying to look up these posts.

 

 

 

 

 

 

 

 

 

[Babak]

Hi, just bringing this subject back up with a quick q.

 

Self building bungalow with habitable first floor (attic) level below 5m height. Lots of steel in attic for purlins and to support dormer walls. 
 

I have installed metal stud frames for walls, the top railings of a couple of which I glued to the lower face of the beams with the idea that when we plaster board we will also cover all steel for fire protection. Rockwool to go inside walls. 
 

Plaster boarder visited yesterday for quote and says I MUST take the railings off to first box in the steel. Is that right? Does not make sense to me given what I have read.

 

I kept asking why the impacted beams must be boxed in rather than be enclosed within the wall space but best he had was it was British Gypsum training/work requirement.

 

FYI I also ended up arguing with him about not needing to double board for boxing in(but happy with fire rated). 
 

Also wanted to double board the ceiling as have some thin steel C-sections used as rafters. Still think 15mm or fire rated boards

should be fine for the ceiling.

It is my own house and will have kids living there but at the same time i don’t want to do something which is completely unnecessary. 30-45 mins is plenty to escape through windows (and we are also fire rating/protecting the stair case for extra measure) but just do not want to listen to someone saying I MUST build it like a 3 storey block of flats if I don’t really have to.
 

Thanks in advance for any advice!

Edited June 25, 2022 by Babak
Typo

[George]

Sounds unnecessary based on my rudimentary knowledge. You may need to get building control advice, though.

[Gus Potter]

On 25/06/2022 at 14:47, Babak said:

Self building bungalow with habitable first floor (attic) level below 5m height. Lots of steel in attic for purlins and to support dormer walls. 

Hope this helps you crystalise your thoughts and good to hear you are using light gauge steel.. always worth considering for attic conversions.

 

For all. A bit of general background info. On a bungalow when converting the attic we consider (not least though) these main elements:

 

1/ Fire prevention..eg making sure that electrical cable sizes are designed for possible embedment in insulation so they don't over heat, correct installation of say wood burning stove flues and so on.

2/ Fire detection and warning.. smoke / heat alarms.

3/ Means of escape should a fire break out. Sometimes called travel distance or, if you have an internal room how you get from that to say and escape window, the sizes of these windows and how high they are off the floor and above the external ground.

4/ How the fire service will effect a rescue should you not be able to escape.

5/ How to protect the fire and rescue service so they are not endangered.

 

It's the last bit of this (item 5) that is probably relevant to @Babak

 

The Scottish fire regs are slightly different but have based the following on the English regs.

 

For a bungalow attic conversion we generally allow the pitched part roof to burn away and fall in. What we don't want is for the attic floor to fall on the Fire Brigade thus we give the attic floor 30min protection. No need to protect rafters, purlins, partition walls in the attic.

 

However there are a few caveats.

 

1/ If you are converting an attic that has been formed from trussed rafters the ceiling chords are often too small compared with a traditional timber cut roof and thus these are often not condusive to achieving a 30 min rating. But you may have had to beef these up anyway to convert the old ceiling chords into attic floor joists. Thus by insulating between the attic floor joists (you may be doing this for sound insulation anyway) and fitting a new floor you may by default achieve a 30 min rating for the new attic floor.

 

2/ Your new attic floor needs to be able to restrain the ground floor walls in a similar fashion to the existing roof when the pitched roof parts and attic internal walls burn / start to fail.. to avoid the ground floor walls falling on the fire service. Again,  if you have been strengthening the attic floor you often achieve this by default.

 

3/ If say the gable end of your house is within 1.0m of a boundary (particularly.. covered in the regs to some extent) then you need to make sure that any masonry spandrel panel does not collapse when the roof burns away. This is very vague in many UK regs / not well understood but in New Zealand their design codes provided some guidance on this aspect.. the UK have yet to catch up / developers  / designers are resisting grasping this nettle in my view. Here your local BC may not explore this with you.

 

In summary I think the bit you need to concentrate on is the attic floor and let the rest just burn away.

 

Have copied extracts from the regs below for reference.

 

 

 

 

[George]

Thanks - that all seems to back up my rudimentary understanding, which could be summarised as:

 

Single dwelling house of 2 stories (<11m) = 30min fire protection to elements which hold up floors, walls or escape routes.

 

Fire protection to roofs not necessary.

 

I suppose the question is, does the dormer class as a wall, or is there further structural support offered by the roof which would warrant fire protection?

[Gus Potter]

@George

 

Hi George. Good summary but where folk get confused is when say a beam that on first appearance seems to be carrying only vertical loading suddenly needs a lot more fire protection, often jumping to one hour when you have a boundary condition. The reason is that often it may be providing lateral restraint to another element of the structure that relies on this lateral support to maintain stability during and after (not covered in the regs but good design should consider keeping our emergency services safe) a fire.

 

I posted earlier some extracts from the English regs earlier (not checked the NI regs yet but assume they say the same). Clause 5.2 covers this. The Scottish regs are similar in this respect.

 

The dormer? My starting point would be to ask.. is the dormer part of the roof / rafters? Is it sacrificial like the rest of the pitched part of the roof. I makes no logical sense that you can let the rest of the roof burn away but have to fire protect the dormer cheeks to a more onerous level as the support stucture for the dormer would have burnt away.

[saveasteading]

A few matters arising.

 

Very few BCOs or Architects really understand fire protection. 

Therefore if you argue then they want something very definitive.

 

Intumescent paint is horrible and expensive. Great for big commercial projects, but even then often misapplied. Most applications are much too thin to provide the protection required. A top coat is required but seldom applied except in big projects.

I once had a painter coat about 200m2 of wall. I told him to go round and round until there was no paint left over, thus providing the required thickness. Next day he told me the 'good news' that he had half the paint left over.

Intumescent paint gets sold with a diy certificate. Effectively it says 'this person bought some of our paint'. I have never known a bco test the thickness/ number of paint pots.

 

Plasterboard is often specified to be fireboard when normal would do perfectly  or two skins of normal. 

Practically, it can be easier to fit 2 skins as the first may be a bit rough and the second is then very easy to fit.

 

In fire tests it has been known for the test to be halted at 30 minutes (60/90 etc) even though the product was still performing. This sells more stuff.