Fire Barriers

[Triassic]

Following on from the discussion about poor build quality? Can we discuss fire barriers in timber frame houses, what are they, where do they go and what are they made of?

[nod]

I’ve read this topic with interest 

The fire bats that I’m using are 1200 x 600 and are made of rock wool ultra dence with  a 3 mil gloss white fire paint on either side 

The ones I’m doing at the moment are wher two rooflines meet one is cut tight and wedges between rafter and wall Rafter should be set off 200 mill minimum Not always though A second layer 250 wide goes over the top Giving 200 mil in total Each layer is sealed giving two hours protection 

Ill snap a picture if I remember 

This system is used on ALL commercial Or a fire curtain system 

 

This large residential job has been stood for ten year when the banks pulled the plug All electrical etc have been rip out and plaster to find that they where relying on two layers of PB to do the job

 

The problem is most site managers don’t really get involved in this sort of thing and rely on the likes of me to get on with it 

BC don’t climb around roof spaces 

They normally take a snap from below 

 

 

[Mr Punter]

@Triassic did you get a design and spec for cavity barriers / fire stopping?

[Triassic]

4 hours ago, Mr Punter said:

@Triassic did you get a design and spec for cavity barriers / fire stopping?

No! Hence the question. To be honest I’d not thought about a fire stop, however I have changed the cladding from larch to fibre cement as we live in a wooded area and we had a woodland fire just down the road last year.

 

The TF company have left a large roll of what looks to be fibreglass inside a 150 x 150mm red plastic sausage. No idea if this the fire stop or how to position It?

[Mr Punter]

This is so typical and as per the other thread it is because nobody is made responsible for specifying, designing and installing this that it so frequently get omitted.

 

Generally with rainscreen cladding you are supposed to have a strongly ventilated gap from bottom to top of your cavity.  This is very much at odds with the principal of cavity barriers, which prevent the flow of air (and fire) between each storey of a building horizontally. You can get intumescent firestopping that expands when heated which would work for the horizontal, but it is very costly.  I got some from Envirograf.

 

It is also sensible to have some vertical barriers to restrict spread of fire around the building so you could divide it up near the corners for example by stapling the red sausage vertically.

 

The fibre cement is a good move.  It is also good to have fire retardant breather paper, but you will normally get what you are given by the t/f co.

 

 

[Triassic]

I like the idea of vertical fire compartmentalisation, I’ll probably fix the fire sausage vertically at the corners, so that each wall is separated in the event of a fire,

 

is is there any guidance on the subject that anyone can link to?

[dpmiller]

Your building regs approved document should have infos- in NI it's document E, 4.36.

[Visti]

+1 on the envirograf ventilated cavity barrier strips. Having to install them around he perimeter of all SOs.

Edited May 2, 2019 by Visti

[scottishjohn]

where would you fit them ?

2 or 3 horizontal rows all round the cavities at different heights?

if at bottom on wall -maybe not get hot enough quick enough to work and stop air flow if fire was upstairs?

seems a very knotty problem to solve simply ,especially if TF  with cladding .

maybe TF should be sheathed outside in MGO board ,which is fire resistant?

a plus of an ICF build maybe ?

and if getting that praniod -the pvc windows will melt out like at grenfell --which caused it to jump and gave it more oxygen 

the right answer has to be sprinklers if you that worried

[Mr Punter]

Sprinklers will not put out a fire in a strongly vented cavity, but they should stop it reaching there.

 

I still can't believe how fire stopping / cavity barriers are such a design / specify / install on the hoof thing where correctly installed they could save lives and buildings.  I would liken it to buying a car and being left to work out how to fit seatbelts and airbags.

[Ian]

On 02/05/2019 at 01:39, Triassic said:

Following on from the discussion about poor build quality? Can we discuss fire barriers in timber frame houses, what are they, where do they go and what are they made of?

I'm not sure why you would need fire barriers in a normal 2 storey detached house unless you have an attached garage. In England & Wales they are not required unless you are building more than 2 storeys or building terraced or semi-detached housing where fire separation is needed on the party walls. Timber frame houses are no different from masonry ones 

Edited May 3, 2019 by Ian

[scottishjohn]

2 hours ago, Mr Punter said:

Sprinklers will not put out a fire in a strongly vented cavity, but they should stop it reaching there.

 

that was my point -fire is put out in room it starts in and limits spread

[Mr Punter]

2 hours ago, Ian said:

Timber frame houses are no different from masonry ones

 

They are when a fire gets into the cavity, because timber is flammable and masonry is not.

[Ian]

30 minutes ago, Mr Punter said:

 

They are when a fire gets into the cavity, because timber is flammable and masonry is not.

The only requirement in the Building Regs is that the cavity is closed at areas such as windows & door positions. The regs list a wide range of suitable materials including timber that can be used to close the cavity at these positions.

 

Edit to show extract from English building regs AD Part B

 

 

Edited May 3, 2019 by Ian

[ADLIan]

Above diag only refers to masonry leaves not timber frame.

[Visti]

As Ian says, it can be any material listed of the appropriate thickness that'll stop the fire progressing for at least 30min.

 

I think the issue is less with Timber Frame vs Masonry construction, but rather more to do with how you clad it:

• Fire resistant material or render - you're ok.
• Timber - got to have a ventilated cavity

It's the ventilated cavity that causes the added requirements, because you can't seal it off 100%... it's got to be ventilated right?

 

At that point you've a cavity between the external wall and your cladding that will need a barrier around the structural openings (doors and windows) as per 6.3, but can't span the whole cavity due it needing ventilation. That is why we're using those barrier strips.

 

If you're using fibre cement rather than timber cladding you should be fine as there'll be no cavity to consider.

[Simplysimon]

fit around every opening and at each corner

[TerryE]

As @Simplysimon says you need them around any fenestration opening which breaches the airgap. And on corners and I would also suggest at the eaves.  There is not need to barriers between floors s in an English 2 two-storey single occupancy dwelling, but they are required n Scotland, IIRC.  The aim of the barriers is limited to providing 30 min protection to allow the house to be safely evaluated.  If its any form of multi-occupancy then the requirements have a step change.

 

Barriers in any penetrations to the internal plasterboard skin is also needed: intumescent pads in the back of all power sockets etc, and a red sausage stop at the top of each service void and any through floor penetrations.  What you don't want happening is a hidden fire within the service void working its way into the floor voids and across flaws.    

[scottishjohn]

it makes you wonder if everyone did it as they are supposed to and were checked by BC on it if we would have so many TF homes 

my guess the cost difference between them and ICF or block+hard plaster  would dissappear very quickly .

does any one really believe that every penetration  of the plasterboard  eg sockets  has a fire stop behind it

thats means then your fire stops should be behind the service void  and that layer is also fire resistant --.

Icf  and hard plaster with electrics buried in the foam under the hard plaster sound a better solution 

fire starts as an electrical one at socket --then set light to the PIR foam insulation-- and the air tightness barrier

Am I missing something ??

[Redoctober]

@Triassic - We built with a TF and they supplied the fire battens which were really what as been described as above - we called them "socks". See the photos for where they were positioned. We used wooden battens to go around the window and door openings.

I hope this helps. 

[Big Jimbo]

Nice bit of stonework Redoctober

[scottishjohn]

@Redoctober

thank  you a very nice example of where to fit fire stops + good looking house

and I presume they are nailed to the frame not stuck to the house wrap,cos if that caught fire they could fall off 

never seen any on houses built up here when under construction  and certainly my own house built( 1978 Tf) does not have any .

when I moved in  and started looking for savings  i found the air bricks were not ducted to the sub floor area --just a grille through outer brick and then a hole in the inner sub wall, force 9 gale up the void between outer brick and TF  ,and definately no fire stops around penetrations like the bog pipe going from top floor to sub Floor.

and top of the cavity wall open where it meets the loft.

when did the requirement for firestops come in?

 

 

 

[Redoctober]

16 minutes ago, scottishjohn said:

@Redoctober

thank  you a very nice example of where to fit fire stops + good looking house

I presume they are nailed to the frame not stuck to the house wrap,cos if that caught fire they could fall off 

 

when did the requirement for firestops come in

 

Thanks - yes nailed on and as for when the regs changed, I have no idea. Sorry.

[Russell griffiths]

Does anybody have experience of any fire stopping needed in an ICF house

timber cladding to some parts and stone on others. 

Might need to ask bco. 

[scottishjohn]

my guess as even cavity wall 2 layers of brick  seems to needs it,then it will be the same 

difference maybe the flammability of the foam around the concrete

never seen it mentioned anywhere .

A guess would be you need to fasten fire stops on to the concrete --in other words remove foam where they fit 

Just a guess though 

that would be a plus for durisol+isotex  (spider ties full concrete shell inc roof)  as the outside is not flammable ,so easy to fix direct to it 

or do they class the concrete as good enough --

sure fire won,t go through it if all penetrations are sealed

,but if fire starts in void --somehow 

then it could race up to the roof  as insulation burns  in void -,

maybe it passes flame spread time test  without need for them 

everything burns if you get it hot enough !!

try setting fire to a spare block bit you have left over

 

 a tricky one 

 

let us know what you find out  please

Edited May 4, 2019 by scottishjohn