New workshop Tin roof Query

[Jonathan S]

Hi all.
I've been scratching my head on this one and thought I would run it past you guy to see what you think.

Long story short, I'm building a terrace (55m2) and a off grid workshop (150m2) with galvanised tin roof covering. The reason for using tin is there is no thermal mass.....I'm up in the Bush in Andalucia Spain and summer temperatures get up to 45° in the shade.
We have lived for 10 years with a terrace roof similar to the attached design, BUT it has no wool or T&G boarding. In the summer its noisy! and hot!
Part of our house has a roof as per the design attached, but instead of wool it has 50mm polystyrene, it's noisy.

The roof noises are from a combination of things, rain drumming (in winter) and thermal creep on the polystyrene (if a cloud comes over the contraction is noisy).
My theory is the wool insulation under compression will stop the drumming and help with the solar creep noise, also help insulate the workshop roof and stop the tin reaching due point.
Traditional here a workshop roof is 10+ meters high so the heat only gets to ground level in late afternoon, my workshop roof will be approximately 3meters.....

I believe this design is simular to how it would be done in Australia.
Looking for criticism so I don't make too many mistakes.

 

[MikeG.]

What span is your roof? A 4x2 will only span 2m or so.

 

[Jonathan S]

What span is your roof? A 4x2 will only span 2m or so.

Mike
Terrace roof is 3.2m span, 4x2
Workshop roof span 3.5m, 6x2
Here the snow comes down to approximately 1200meters
We are at 350meters, so no snow thankfully.
I could up the terrace roof to 6x2 but was hoping with a light weight tin roof 4x2 would work.

 

[MikeG.]

For those spans, you need 6x2s at 400 centres. That's without a snow load. If snow is any sort of possibility, then those need to be 8x2s.

 

[Jonathan S]

Ok Mike, it will have to be 6x2.
In this part of Spain they only sell 8x2 is 1st quality and thats in random lengths.

My main concern is the noise from the tin roof and hoping someone had something to say with putting the tin under compression with the wool.

 

[sometimewoodworker]

Ok Mike, it will have to be 6x2.
In this part of Spain they only sell 8x2 is 1st quality and thats in random lengths.

My main concern is the noise from the tin roof and hoping someone had something to say with putting the tin under compression with the wool.

We have colorbond roofing. In the workshop it just has PU foam, it’s just been raining and I need ear defenders to listen to any podcasts. In the main house we have that + a plasterboard ceiling which has fibreglass insulation on top and it is very much quieter Start here how much sound reduction you will get will depend on the amount of compression of your wool.

 

[Hornbeam]

Profiled galvanised or prepainted steel roofs can be designed to give quite good acoustic performance but you need to consider number of factors
Stiffness. The sound you hear from rain drumming is caused by the steel roof vibrating. The stiffer the roof profile the less noise. Ways to improve stiffness are use a deeper profile, thicker gauge and reduce the spans (best would be fully supported on OSB or similar
Separation. If you use a quilt insulation then you are separating the vibrating steel outer skin from the inside of the building. Conversely a rigid PUR insulation board toughing the steel outer sheet will transmit the vibrations straight through. ( I would not recommend polystyrene due to fire risk)
Mass. Adding mass into your roof covering makes it much slower to respond and is particularly effective for lower frequency noise
Best approach would be a fully supported steel profile using OSB with glass wool quilt underneath and a lightweight internal liner sheet to retain the glass wool and give a good internal surface. Dont forget to consider moisture (humid air and condensation)so consider where it can get in and out
Because of your location If using pre painted steel ask your supplier about the resistance to UV performance. You want a product with RUV 4 otherwise is will change colour /chalk quite quickly
Ian