Fill Gaps in Loft Party Wall - Joist Through Party Wall

[simonp85]

We recently moved into a semi detached property that's not been touched for many years. As well being utterly filthy and having no insulation at all we're concerned by the fairly large holes through the party wall.

The ceiling joists all end in these gaps in the party wall that extend fully into the neighbouring loft space. In the first photo below you can see our joists extending into the holes and the ends of the neighbour's terminating in the gaps.

In addition to this we're getting a lot of noise through the party wall. In all the spaces adjacent to the party wall we can hear the neighbour's conversation almost as if there's no wall there at all. This is no doubt not entirely down to these holes in the party wall in the loft but it can't be helping.

Would appreciate advice please on how best to fill and seal these holes, in particular with a focus on eliminating as much sound transfer as possible. We want to get these properly sealed up before laying much needed insultation.

Many thanks.

 

[jj4091]

fireproof expanding foam - Google Search

 

[DAZB]

This may do the trick and can be trimmed flush when set....

Soudal Genius Gun Fire & Acoustic Expanding Foam

• Fire class DIN 4102 B1• Fire resistance, B2 up to 2 hours & B1 up to 4 hours depending on joint configuration• Acoustic rating - 58 dB• Insulation factor - 36mW/mK• Interior and exterior useRapid curing B2 Fire Class expanding foam with Genius Gun applicator for accurate trigger control and...

www.toolstation.com

 

[Ivor Windybottom]

Is it a single brick skin? If so you'll always be able to hear each other, as it's essentially an internal wall. The only way to improve this would be for one or both of you to donate some of every room to making it thicker. There's no miracle paint or wallpaper that can do this.

But, if it's a house, then it's possible/likely that the joist ends in the floor/ceiling between the floors have the same issue. If so then sealing these gaps would be very beneficial. You'd need to lift some floorboards on one side to check and fill. Perhaps you could share the disruption between you, e.g. you mess up your front room, they do their back room or something.

 

[^woody^]

Fire foam is not rated for gaps wider than 50mm.

Pack with rockwool first, for better sound and fire insulation, then foam.

 

[simonp85]

Thanks all, super helpful.

Is it a single brick skin? If so you'll always be able to hear each other, as it's essentially an internal wall. The only way to improve this would be for one or both of you to donate some of every room to making it thicker. There's no miracle paint or wallpaper that can do this.

But, if it's a house, then it's possible/likely that the joist ends in the floor/ceiling between the floors have the same issue. If so then sealing these gaps would be very beneficial. You'd need to lift some floorboards on one side to check and fill. Perhaps you could share the disruption between you, e.g. you mess up your front room, they do their back room or something.

According to the plan for the properties it is double brick, however in the loft space where they've used the concrete blocks this section is single skin - so in the loft at least the two layers of single skin concrete blocks are topped by a double brick skin with an air gap. However the internal walls are all rendered so without removing this we've no way of knowing if this pattern of single skin concrete block / double skin red brick continues below.

Regarding the floor joists - we've already been under the floors for other works and confirmed that these do not go through - our floor joists terminate against the party wall and are supported by a dwarf wall, so thankfully no gaps through the wall on the floor joists, just the ceiling.

 

[noseall]

We recently moved into a semi detached property that's not been touched for many years. As well being utterly filthy and having no insulation at all we're concerned by the fairly large holes through the party wall.

The ceiling joists all end in these gaps in the party wall that extend fully into the neighbouring loft space. In the first photo below you can see our joists extending into the holes and the ends of the neighbour's terminating in the gaps.

In addition to this we're getting a lot of noise through the party wall. In all the spaces adjacent to the party wall we can hear the neighbour's conversation almost as if there's no wall there at all. This is no doubt not entirely down to these holes in the party wall in the loft but it can't be helping.

Would appreciate advice please on how best to fill and seal these holes, in particular with a focus on eliminating as much sound transfer as possible. We want to get these properly sealed up before laying much needed insultation.

Many thanks.

View attachment 347715

View attachment 347714

That is one weird joist set-up... What is stopping the roof from spreading? A king truss or summat?