BUILDING CONTROL WANTS FIRE RESISTANT WALLS . Passivhaus standard wants breathable walls. Which one is it.

[Patrick]

Got an issue which i can not figure out what to do .

1 side of our building is to a neighbouring property (within 1m) . So building control requested Fire proofing of the wall. Building is timber frame so they want us to use something like Promat SUPALUX . Very expensive boards for outside sheeting . It supposed to go over the outside boarding/sheeting of the walls , behind the cladding (which also needs fireproofing) 

But we specially sheeted the outside of the walls with Panelvent DWD to have the walls vapour open to the outside. This is complete opposite now , putting a cement board on top of it. Pointless to do a Panelvent board to the outside in the first place.

I looked around, got in touch with a few companies and there used to be a vapour open fire resistant board called Econic General Purpose Sheathing Board (breathable, fire resistant) .... BUT its not getting produced anymore. At the moement the website just states they need to update the boards to latest regulation standard.

 

Anyways. I surely cant be the 1st to have this problem.

Anybody came across the iussue ? how do i fireproof the walls ? 

without putting any non-breathable sheets to the outside.

 

 

 

[Conor]

Is this to stop external fire spread (i.e. the timber structure or cladding) or contain fire within the building? If the latter, you could see of they accept fire rated plasterboard on the inside?

Edited December 9, 2021 by Conor

[nod]

It’s quite normal to be asked to do this 

You could ask for a second opinion 

[saveasteading]

More information needed.

The avoidance of fire spreading from your house to another is the main concern, and the likeliest cause is through a window. Have you any on that wall?

Then there is the spread of flame on the outside of your wall....if you have proposed timber cladding can't you just delete it?

 

Plasterboard internally works perfectly well and there is  no need to get complicated.

 

Being 1m or less makes it more onerous but it should be easily resolved I feel.

Anything that is not sold as vapour-proof will likely be porous and breathable, so I suggest moving away from niche products towards traditional. With 1m gap it is not as if it will be visible and a feature of the building.

[nod]

It is quite normal I hardly came across this up and till recently  Now all the large companies do this as a matter of course 

Its simply a fire break to protect your neighbor 

 

[Patrick]

1 hour ago, Conor said:

Is this to stop external fire spread (i.e. the timber structure or cladding) or contain fire within the building? If the latter, you could see of they accept fire rated plasterboard on the inside?

Former. The later isn't a problem. As you rightly said. Plaster board will solve this.

[Patrick]

43 minutes ago, saveasteading said:

More information needed.

The avoidance of fire spreading from your house to another is the main concern, and the likeliest cause is through a window. Have you any on that wall?

Then there is the spread of flame on the outside of your wall....if you have proposed timber cladding can't you just delete it?

 

Plasterboard internally works perfectly well and there is  no need to get complicated.

 

Being 1m or less makes it more onerous but it should be easily resolved I feel.

Anything that is not sold as vapour-proof will likely be porous and breathable, so I suggest moving away from niche products towards traditional. With 1m gap it is not as if it will be visible and a feature of the building.

It s not internally. It's external. It's also not about visible. I would love to use a traditional product. There is none (to my knowledge) . Outside cladding is wood but even with other forms of cladding the timber frame itself still would need to be made fireproof to the outside .

[ETC]

Move the wall to comply or build the wall in masonry.

[Gus Potter]

Good comments from all.

 

Hope this bit of background info helps you navigate the fire regs. Have made posts in the past about this but can't find the links etc.

 

In the UK the fire boundary conditions were developed off the back of the fire of the great Fire London. In principle they recognised that is it not accepable for your house to go on fire and set light to your neighbours house. It's ok for your house to burn.. so long as you don't say endanger say the Fire Service personnel and make sure you can escape from the building and so on.

 

Jumping forward in time the fire boundary conditions in the regs were based on the principle that if you build within say 1.0m of the boundary then your wall has to do a number of extra things. The fire tests and specs in the regs are based on you not setting light to your neighbour. The regs and tests don't take into account that your neighbour may set light to your house!

 

The wall as Nod says essentially provides a fire break. Ok that's the easy bit.. please bear with me!

 

Lets take a TF wall as it is harder to deal with cf a solid brick 225mm wall.

 

The first thing (there are other ways of doing this where you split the loads under fire conditions.. too much for now) is that your TF wall needs to stay up. The fire is on the inside. To stay up you protect the timber frame that is the structural element.  Could be plaster board on the inside or a material that does two things:

 

1/ It needs what is called integrity. You may see a material that if it is fixed in a certain way it will give you 60 minutes integrity. Integrity means that say a sheet of plaster board will not split in the middle but also not fail where it is fixed at the edges. You can see if the edge fixings fail the board it will come loose and the flames/ sparks will bypass the sheet. Integrity is lost.

 

2/ You also see what is call "insulation" Here we look at how much radiant heat will be emitted by the covering / material on the side away from the heat source. Think of this as having an electric fire.. no sparks or flames but the radiant heat will set light to say the TF. The same principle applies to the whole wall.. you can't just stop flames and sparks going over the boundary you also need to stop radiant heat.

 

Now to get the fire "resistance" of materials (which is what you often see mentioned) used on a fire boundary wall we look at both the intergrity and resistance to get a value of performance. The Eurocodes present slightly differantly but I hope you have got the jist of it.

 

The idea with TF is to make sure the frame stays intact,  up right (with some deflection) and does not fall on the Fire Brigade or others.

 

Lastly we look at the outside surface on your neighbours side. We recognise that you should not put a flammable material on the outside face of a boundary wall next to your neighbours. We know that sparks do fly about so that is partly where the surface spread of flame requirements come from. For example.. a pine timber untreated on a boundary has a high risk of propagating surface spread of flames from a spark.

 

If you can get your head yound the principles then it makes it easier to select your cladding.

 

Lastly when you compare some of the regs in Scotland cf England you could conclude (apparently) that Scottish fires are hotter than English fires!

 

 

 

 

 

 

 

 

 

 

 

[Temp]

Would you be allowed something like...

 

Decorative cladding

Fire barrier/SUPALUX

Ventilated Cavity

Panelvent DWD

Timber frame

 

Ventilated cavity would allow breathability but  would that meet fire regs?

[Patrick]

1 hour ago, Temp said:

Would you be allowed something like...

 

Decorative cladding

Fire barrier/SUPALUX

Ventilated Cavity

Panelvent DWD

Timber frame

 

Ventilated cavity would allow breathability but  would that meet fire regs?

That is the point I was making but apparently this is not allowed. I will retest them on this topic . I think I might think about a brick cladding in that position.

The funny thing is, there is no neighbour. His house is 50m away. Just the end of his garden. But I built right next to the garden wall so counts as "within 1meter" . No getting around that.

[saveasteading]

4 hours ago, Patrick said:

I would love to use a traditional product.

 

Timber in a wall doesn't burn unless flame reaches it. Therefore if you delete the external cladding, and then skin the timber structure in masonry or cement board (and render) does that not resolve the issue?

 

The absence of a neighbour isn't the issue, as they might want to build close to the boundary in future. The rule can be relaxed if there is little possibility of that happening eg there is a river , pond, road etc.

[Dan F]

We have this same issue with timber-frame  garden room within 1m of the bounday.  Rather than use fire boards externally, we plan to just use a render system with the relevant fire rating.

Edited December 10, 2021 by Dan F

[Dreadnaught]

I had this issue too with my timber frame.

 

I swiped the external Medite Vent sheathing board for MagPly and building control accepted it.

I also swapped the breather paper from Protect TF-200 to Tyvek Firecurb. 

The MagPiy was actually suggested by Building Control. 

 

My external cladding on the sides close to the boundary is Cedral Lap (with a ventilated void) so I did not need to change that.

[ETC]

You’ll need a tested framed system to give you 1HRFR. 

[Patrick]

1 hour ago, Dreadnaught said:

I had this issue too with my timber frame.

 

I swiped the external Medite Vent sheathing board for MagPly and building control accepted it.

I also swapped the breather paper from Protect TF-200 to Tyvek Firecurb. 

The MagPiy was actually suggested by Building Control. 

 

My external cladding on the sides close to the boundary is Cedral Lap (with a ventilated void) so I did not need to change that.

Thats extremely helpfull, thanks.

 

@Dan F this was my plan B to just do render or Bricks.

[Dreadnaught]

1 hour ago, Patrick said:

Thats extremely helpfull, thanks.

 

A couple of other things to note on MagPly:

1. Its breathable. 
2. Its strong. I only needed 9mm thickness of MagPly to replace 12mm of Medite Vent sheathing board,
3. Some of the building warranty companies don't like magnesium oxide boards in general, for reasons I don't understand, including LABC I think. Might be worth double checking with your warranty provider, if you have one, beforehand it if you are thinking of using MagPly.

https://www.magply.co.uk/applications/timber-frame

[saveasteading]

2 hours ago, Dreadnaught said:

Some of the building warranty companies don't like magnesium oxide boards in general,

https://www.nhbc.co.uk/builders/products-and-services/techzone/technical-updates/magnesium-oxide-building-boards

[jonM]

We coated the wooden cladding on the gable ends with envirograf  https://envirograf.com/product-category/fireproof-coatings/  which was accepted by building control. 

We used envirograph primer, two coats of fireproof coating and two coats of osmo. Envirograf are very helpful if contacted. 

 

 

Edited December 12, 2021 by jonM

[saveasteading]

5 minutes ago, jonM said:

two coats of fireproof coating

 

Have used Envirograf for decades. A small company with good customer service and very good technical advice: they wont just sell it if it is not the right product.

They even made up seal coat to a special colour to avoid an additional decorative coat (but that was internal use).