Timber Frame Options for External Noise

[Tim_C]

My site is about 50m from a railway line, so external noise is a consideration when deciding on timber frame spec. For all options the aim is for high airtightness, triple glazing and assumes fibre cement external cladding (or similar)

 

As I see it we have these options:

1. 140mm studs (PIR between)plus 25/50mm internal PIR. Cheapest but I assume worst for sound transfer.
2. Same as option 1 but additional sound boarding internally (e.g double plasterboard, acoustic plasterboard).
3. 300mm twin stud filled cellulose. I understand this is best, but more expensive with thicker wall buildup.
4. Other options I haven't thought of?

 

So I have a dilemea, with a trade off between cost/sound insulation and wall thickness. I'm trying to understand if the premium options are worth the additional price. What are people's experience of these options in the real world? Or any other options worth considering?

[-rick-]

Rockwool (or similar heavy mineral wool) installed instead of PIR. Rockwool is less insulating that PIR so would need thicker walls if you want the same level of insulation. You are already looking at high levels of insulation (beyond legal minimums - which themselves are a lot stricter than they used to be) so maybe the reduced insulation doesn't matter if you kept the wall thickness the same*. If it does a compromise is to do rockwool between the studs but keep the PIR internally. Not as good sound insulation but better thermally.

 

My other thought is to consider what you are doing between the house and the rail line. Trees? Hedges? Fences? Even a rain screen that is somewhat isolated from the main building structure may help stop noise getting to the walls in the first place. Having said that ignoring the railway I would personally avoid option 1 anyway. The decrement delay and sound insulation properties of mineral wool/cellulose/similar are a great advantage for any property.

 

* Beyond a certain point you might gain more from investing in better airtightness/good MHVR than having thicker insulation.

 

 

[-rick-]

Based only on watching grand designs in the past (memory is vague). I seem to recall a lot of 'noise' can be transmitted through the soil as a lower rumble. IIRC there are some mitigations you can do about this so that may be worth researching too.

 

Depends a fair bit on what sort of railway is nearby. Fast passenger trains, slow commuter trains, freight?

[Bramco]

You also need to take the roof into account.  Especially if you are planning vaulted ceilings.

[JohnMo]

Any option that includes PIR is a bad option as it noise transparent more or less.

 

Why not a heavy structure instead of the lightweight ones suggested i.e. concrete blocks, woodcrete ICF etc

[Nickfromwales]

400mm of blown cellulose in the roof, 300mm in the walls.

 

Feckin graveyard silent.

 

1. Dogshit.

2. Slightly less dogshit.

 

(by comparison).

 

FYI, this isn't me just giving my opinion from AI ramblings, I have been in all types of new construction for various clients since around 2012, building with 'higher performance' offerings, and the cellulose is in an entirely different universe here.

 

On 31/07/2026 at 13:20, -rick- said:

I seem to recall a lot of 'noise' can be transmitted through the soil as a lower rumble.

VERY good point, but a lot of the 'clack' from the tracks is much higher frequency; ask me how I know, as we used to live 150m from the track from the local colliery and I can still hear it sat here right now, engraved in my memory from my teens (I am now 52....). I doubt you'll hear much of the engine sounds, but the clack from the wheels hitting the joints is defo worse between slower and faster speed; slow as I remember was almost like a heartbeat type of pattern, for an age it seemed to take to pass.

 

Freight can be twice the length of passenger too, or more, so choose once, choose well, or regret forever.

 

On 31/07/2026 at 13:05, Tim_C said:

What are people's experience of these options in the real world?

I did one build in Dorset for 'a woman' and the plot wasn't far from Yeovil. It was an MBC TF PH offering with the aforementioned 400 + 300mm cellulose blown roof/frame.

 

When the Chinook helicopters passed over the noise was incredible, and if we were outside talking you simply had to stop, wait 5 mins or more, then begin shouting again to be able to hold a conversation. However, if you simply stepped inside the house and shut the (Norrsken) front door, it was as if the chopper was another 15 mins away, and you could talk normally without hinderance.

 

Choose well.  Sleep better  

[-rick-]

7 hours ago, Nickfromwales said:

VERY good point, but a lot of the 'clack' from the tracks is much higher frequency; ask me how I know, as we used to live 150m from the track from the local colliery and I can still hear it sat here right now, engraved in my memory from my teens (I am now 52....). I doubt you'll hear much of the engine sounds, but the clack from the wheels hitting the joints is defo worse between slower and faster speed; slow as I remember was almost like a heartbeat type of pattern, for an age it seemed to take to pass.

 

Indeed, modern fast lines are all welded rail so shouldn't clack unless travelling over points. Noise profile their will be very different to a rickety old freight line with heavy aggregate trains back and forth all day.

[Tim_C]

On 31/07/2026 at 13:20, -rick- said:

what sort of railway is nearby

 

It's a slow section of un-electrified line (I believe 50mph), with no points in the proximity. I don't hear any 'clacking' and from what I can see its welded rail. So I believe the main noise will be external from freight diesel engines and squealing of freight wagons. 

 

13 hours ago, Nickfromwales said:

Dogshit

 

Thanks all - sounds like best to avoid PIR then 😅  The downside is it narrows the field a lot in terms of TFs from the usual TF suppliers, which are high performing thermally (but aren't twin stud cellulose).

 

On 01/08/2026 at 08:39, JohnMo said:

Why not a heavy structure instead of the lightweight ones suggested i.e. concrete blocks, woodcrete ICF etc

  

Aiming for high airtightness, insulation levels and convenience (e.g a subcontracted package) was leading me towards a TF from one of the usual suspects. But would consider ICF if it ends up being a better compromise. For noise, where do we would think ICF ends up compared to the twin stud cellulose?

 

[JohnMo]

10 minutes ago, Tim_C said:

Aiming for high airtightness

All build methods can achieve that.

 

11 minutes ago, Tim_C said:

subcontracted package) was leading me towards a TF from one of the usual suspects.

Specify exactly what wall thickness you want, because its normal for say 140mm, nothing stopping you saying I want 200mm, then do it in I beams or posi joists style. If restricted to 140mm and then apply counter battens to increase wall thick and get rid of most thermal repeat bridges. Then any high density insulation you want.

[Mr Punter]

Rendered concrete block outer leaf, 50mm cavity, Rockwool insulation between 140 studs, 40mm PIR, 25mm service cavity, resilient bars, plasterboard.  Inexpensive and very effective.  Less than 400mm.

Edited 4 hours ago by Mr Punter