head of firewall protection

[CharlotteJ]

Hi, our structural fire wall between two dwelling (single storey) will be pink boarded both sides and continues up into the roof space, to underneath the roofing felt.  Is it acceptable to cover the head of the firewall (where it would meet the roofing felt) with pink fireboard also, we will fill any joins between head of wall plasterboard and wall plasterboard with appropriate fire rated sealant.   Or must I use a specific product for this? There will be additional firestop between battons and roof tiles as required. Thanks for any help given.

[Nickfromwales]

Follow the details provided by your architect / SE and double-check with your BCO.

 

If a fire is involved to the point that flames are at the ridge, then there will be nothing to save anyways, so I doubt capping that head is of any importance; unless otherwise stated by your principal designer.

[nod]

If it’s a stud wall Don’t forget to board and seal under the sole plate 

[CharlotteJ]

Thanks for your reply.  The sole plate is being fixed to existing concrete floor so I didn't think we would need to put pink/fireboard under it?  We are boarding tight to the concrete floor (on DPC) then use the fire rated mastic where the board meets the floor - same with where the stud is against the block wall - we will board tight up to the wall and then fire rated mastic between the edge of the board and the block wall.  Is this acceptable in your opinion? Thanks

[CharlotteJ]

On 17/06/2025 at 20:18, nod said:

If it’s a stud wall Don’t forget to board and seal under the sole plate 

Sorry, meant to quote your reply......

 

Thanks for your reply.  The sole plate is being fixed to existing concrete floor so I didn't think we would need to put pink/fireboard under it?  We are boarding tight to the concrete floor (on DPC) then use the fire rated mastic where the board meets the floor - same with where the stud is against the block wall - we will board tight up to the wall and then fire rated mastic between the edge of the board and the block wall.  Is this acceptable in your opinion? Thanks

[nod]

You do

and two lines of acoustic sealant to the floor 

You need your stud to be a fire compartment 

[Nickfromwales]

42 minutes ago, nod said:

You do

and two lines of acoustic sealant to the floor 

You need your stud to be a fire compartment 

Intumescent / acoustic yes?

[saveasteading]

In real life you don't need to seal that interface. There's no way that fire can get through a zero gap. Plus wood chars but doesn't burn,   plus the concrete and plasterboard will expel water at thd board ends.

 

But  a bco doesn't know that and wants to see an industry standard drawing and the same built.

 

So use beads of intumescent mastic at the ends.

 

Where it meets the roofing felt,  what happens? Felt burns and drips flame. Then is there any board? 

The fire can jump next-door. 

I think you need to fireboard the soffit for a metre on both sides. But I havent checked the document.

Edited June 20 by saveasteading

[CharlotteJ]

33 minutes ago, saveasteading said:

In real life you don't need to seal that interface. There's no way that fire can get through a zero gap. Plus wood chars but doesn't burn,   plus the concrete and plasterboard will expel water at thd board ends.

 

But  a bco doesn't know that and wants to see an industry standard drawing and the same built.

 

So use beads of intumescent mastic at the ends.

 

Where it meets the roofing felt,  what happens? Felt burns and drips flame. Then is there any board? 

The fire can jump next-door. 

I think you need to fireboard the soffit for a metre on both sides. But I havent checked the document.

We've been recommended Sikacryl®-620 Fire to seal the joints where the plasterboard meet and along edge where board meets concrete floor or block wall.  Wood wall plate is covered with pink board and extended each side. We've pink board directly beneath the felt, which meets the top of the fire wall and again, joints sealed.  I will check the plan for the soffit.  Thanks so much

[nod]

4 hours ago, saveasteading said:

In real life you don't need to seal that interface. There's no way that fire can get through a zero gap. Plus wood chars but doesn't burn,   plus the concrete and plasterboard will expel water at thd board ends.

 

But  a bco doesn't know that and wants to see an industry standard drawing and the same built.

 

So use beads of intumescent mastic at the ends.

 

Where it meets the roofing felt,  what happens? Felt burns and drips flame. Then is there any board? 

The fire can jump next-door. 

I think you need to fireboard the soffit for a metre on both sides. But I havent checked the document.

and how many firewalls have you installed 

In real life 

[saveasteading]

16 hours ago, nod said:

how many firewalls have you installed

In real life 

Probably about ...I don't know. 

Guess 300? 2.2m high min, to 8m max.

 

Mostly me drawing or standing watching,  and seldom  wielding the stanley knife.

 

I'm maybe missing your point.

 

What I mean is that a fire would not spread under that even without intumescent mastic.

I guess a really poor sole-plate fitting where you could see light through, might be a slight risk IF the blaze was intense and there was pressure forcing air through and a floor level fuel source.

 

I've been informed that tests show that a 3mm gap between plasterboards onto stud,  does not create any risk.

 

 

But if there is sealer, for a  few more £,  then everyone is happy.