Question for builders

[Arm]

Hi. Quick question for the builders. Doing a house extension and seems normal nowadays to put acoustic insulation in the ceiling / first floor floor. Do I have to ? This room has an open staircase so open anyway to noise. It’s an open plan layout with upstairs open balcony.

I’d rather leave the joists open for access in future than to insulate.

Thoughts ?

cheers

[stephenh]

I don't know the answer, Ash, but it is a building regulation question really. house builder, or architect or building surveyor might be able to answer?

[wizzer]

best bet just ask building control , different authority's have different rules.

Tony 

[Mark (smokey mow)]

If its an extension then yes sound insulation will be required within the floor to comply with Part-E of the building regulations.  The only exception would be if you are using composite joists that have a registered robust detail which may allow for it to be omitted. 

the insulation in the floor deals with impact noise, whereas of couse sound carrying up the stairs would be airbourne noise so the purpose is very different.

[Arm]

Thanks. I have used the composite floor joists hence part of my issue. The joists are open lattice and would be difficult to fully fill.

 

Is that what you mean by registered robust detail ?

[Mark (smokey mow)]

1 hour ago, Arm said:

Thanks. I have used the composite floor joists hence part of my issue. The joists are open lattice and would be difficult to fully fill.

 

Is that what you mean by registered robust detail ?

Yes. If you can tell me exactly which system you've used (TJI, JJI or easi-joist etc) I can check it out for you to see if the insulation is needed.

[Arm]

Hi. These are posi joists.

Now I know it’s a building reg, and it was on the drawing, I’d better do between the joist and careful fill all gaps. I wasn’t planning to double plaster board or put another layer above floor.

Unless it’s completely exempt.

Ash

[Mark (smokey mow)]

It looks like, providing you are using either a 225mm or 253mm joist and have a 15mm wallboard to the ceiling (rather than the usual 12.5mm) then you wont need to install any accoustic insulation within the depth of the joist.

 

[Dave Eastwood (Gadgetman) - Club Chairman]

Sorry for interruption.

But this is why I love the Boardroom. Not just hearsay advice, but genuine expert help, virtually no matter what field!

[Arm]

Wow.

mine are 253 mm joists , 12.5 mm plaster board, 5 mm skim, 22mm chipboard. 8 mm underlay and 8 mm veneered floor.

Looks like I will be close . Would that be sufficient ?

 

I hoped to wrap pipes only but if I have to would do whole floor.

dilemma

 

[Mark (smokey mow)]

Its close, but i'm sorry to say probably not quite enough. If 12.5mm board was ok then i'd expect to see that rather than 15mm in the table. i'd also be suprised if your plaster skim is 5mm as usually it would only be 3mm but even then the densiity of plaster is much lower than wallboard and its mass you need in this instance for the sound absorption. 

For the minimal cost of the insulation I'd be inclined to fit it.  The sound insulation limits in the Building Regulations are a minimum standard and a pretty poor one at that.

[Arm]

Any indication I could do 50 mm acoustic with these 253 joists ?

Happy to do it. 

[Mark (smokey mow)]

It's one of those questions that isn't quite as easy to answer as you might think.

 

The detail in the building regulations approved document which the architect had worked to is in effect a fit all solution and "one way of complying with the requirement of the regulations". The robust details from the manufacturers on the other hand are based on physical laboratory testing of that detail to demonstrate compliance but only if you follow that detail exactly.

 

If I was to be approached at work with a similar question then I would probably be asking you to fit 100mm as in the absence of a robust detail or other test data I'd have no way to know if 50mm would be sufficient or not.

[Arm]

Ok many thanks. I will do the 100mm. It’s no big issue and not worth even debating with the B/C guys.

cheers

ash

[Arm]

Hi Mark. Mind if I ask another quick question ? Have moved up with the build to the sloping upstairs ceiling and dont know if im reading this correctly.

So 100 mm pir board between the rafter then insulated plaster board (12.5 mm plasterboard bonded to a 25mm pir) underneath ?

Or an additional layer also ?

Thanks

Ash