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Sound insulation for metal roof?

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Prizen

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Hi all

My block wall shed has a metal roof. It has no insulation and and their noise levels outside are higher than what would be acceptable to my neighbours.

just wondering if there is a cost-effective way to install sound insulation on the roof that won't cause any issues with moisture?

Thanks
 

Hornbeam

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There are three main approaches to reducing sound transmission. Increased mass, Increase stiffness . Increase separation by having 2 skins
A single skin metal roof construction gives about 24db airborne sound reduction. . Insulation on the underside will leave the rafters acting a localised bridging and not be that good
The simplest way to improve the performance will be to effectively turn it into a twinskin insulated structure. Do this by using spacer brackets to create a cavity depth on the top install a layer of around 30mm dense acoustic slap and 100mm of light insulation quilt and then a top sheet. Doing this will give you around 40db reduction and a thermally efficient roof so less condensation issues etc.
Only 16db increase in performance may not sound a lot but the db scale is logarithmic so its quite a lot.
Note the db figure quoted are approximate (but based on work test data) the performance varies across teh frequency range and is generally better for higher pitches.
Insulating the roof may not be your only issue as sound will transmit through all parts of the building and it is a bit like water so it is teh weak parts in the construction that cause the problems (doors/windows/thin block wall) The block wall probably less of an issue due to high mass.
If you want more information drop me a pm and I will have a look in work
Ian
 

wsb1207

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Can you put joists at wallplate level to span the shed? If that's possible, the most cost effective way would be to insulate as a loft space and plasterboard or osb your new 'ceiling'.
 

thetyreman

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I'd have thought lining with rockwool will do an acceptable job stuffed in the gaps then line/skin the inside with plywood, and seal it up with caulk, ideally you want something like tecsound S100 as a barrier but it's not cheap! make sure there are no gaps in the roof seal e.t.c, even a tiny less than 1mm gap will leak huge amounts of sound energy into the room.
 

Prizen

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Thanks all. How effective would stuffing Rockwool sound insulstion between the rafters ?
This would be my idea of the simplest option but I don't want to Shell out for little or no noticeable benefit
 

Inspector

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You need an airspace between the insulation and the roof. If you don't you risk the roof rusting from condensation. There doesn't look to be enough depth to put batts in and have that airspace, so you are stuck with adding material to the undersides to increase the depth or as wsb1207 suggested create a flat ceiling with drywall or sheet goods of some kind and insulation on top. Then your roof is vented, able to dry and the sounds stay in with you. The flat ceiling is easier to paint white which will brighten up the place immensely.

Harder and more costly is buy all you surrounding neighbours homes and have nobody around you to gripe. ;)

Pete
 

Brandlin

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Prizen":1af2o12k said:
Thanks all. How effective would stuffing Rockwool sound insulstion between the rafters ?
This would be my idea of the simplest option but I don't want to Shell out for little or no noticeable benefit
Not very. the rafters will carry the vibration straight through to roofing material. Those insulation materials are designed to absorb sound energy and be used in conjunction with a gap to create a twin wall.
 

sunnybob

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I think that needs qualifying. rockwool, packed medium tight, will greatly reduce sound transference. The wooden rafters will transmit SOME vibration, but unless you are after a completely sound PROOF barrier, not very much.
Using rockwool under floors in houses is an amazing sound deadener as well as insulator.
But as said, in your particular case, with a tin roof, condensation is your major concern with insulation.
 

Hornbeam

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thetyreman":1xos4uhp said:
best to measure sound in dBA so that it's an average level
dBA and average figures can be very misleading. It is much better if you have an actual idea of the frequencies you are trying to to stop. Lighter weight constructions can work well for higher frequencies ( high pitch router) but lower pitches probably more like a planer then mass is best
Extract from a tech paper I wrote several years ago shows how much sound reduction can vary with frequency for different constructions
https://www.tatasteelconstruction.com/s ... _FINAL.pdf
Installing a false ceiling with dense mineral wool on top will work well but it will reduce teh volume of your workshop and make it noisier internally
Also as an aside most insulated metal cladding systems do not require air cavities provided the inner sheet is properly taped during installation
ian
 

thetyreman

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Hornbeam":2d7a031m said:
thetyreman":2d7a031m said:
best to measure sound in dBA so that it's an average level
dBA and average figures can be very misleading. It is much better if you have an actual idea of the frequencies you are trying to to stop. Lighter weight constructions can work well for higher frequencies ( high pitch router) but lower pitches probably more like a planer then mass is best
Extract from a tech paper I wrote several years ago shows how much sound reduction can vary with frequency for different constructions
https://www.tatasteelconstruction.com/s ... _FINAL.pdf
Installing a false ceiling with dense mineral wool on top will work well but it will reduce teh volume of your workshop and make it noisier internally
Also as an aside most insulated metal cladding systems do not require air cavities provided the inner sheet is properly taped during installation
ian
I said it would do an 'acceptable' job which means it's not ideal, it'll be better than how it is now but not perfect, I will have a proper read when I have the time, it's a LOT of info to take in though :D
 

Prizen

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] Also as an aside most insulated metal cladding systems do not require air cavities provided the inner sheet is properly taped during installation ian[/quote said:
Sorry I don't understand. What is the inner sheet? I assume it doesn't apply if I just stuff Rockwool between the rafters. Tks
 

Hornbeam

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Inner sheet refers to a standard twin skin built up insulated system which is not what you have.
Just stuffing rockwool between the rafters will give you a fairly poor result because much of teh noise will transmit through the rafters. Also ainy water vapour in teh air will permeate through the insulation and condense on the underside of the cold outer sheet, which will then drip into your insulation. Note your condensation problem will be very little different from what you have now
Ian
 
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