steel sheet house roof - how is it done?

[bobk]

My little barn roof is covered with wriggly tin & there are four Velux windows fitted to the North elevation. There is 100mm of insulation between the 150mm rafters @ 400mm centres. All/any gaps are filled with foam to stop draughts. Tyvec is then laid tight over this & stapled followed by 175mm x 50mm treated battens @ 500mm centres. The wriggly tin is fixed in the usual way with self drilling screws although careful marking and a punch helped to start the holes. Pitch is 35 degrees.

Air flow is important both above and below the Tyvec. There are air holes drilled in the ridge-board and there are soffit vents too. All electricals are in a dedicated run under the Tyvec so I can have a clean view of the x 4 douglas fir trusses that I made a while ago. Careful attention was paid to the join of the cavity & roof insulation, again to stop any draughts.

When I finish inside there will be 180mm of insulation as I will fix 70mm to the underside of the rafters to stop cold bridging followed by insulation backed plasterboard then plaster. The walls are 350mm wide insulated cavity and I lead with the inner. ( blockwork goes up first) Not forgetting Flemish bond brickwork.
SS

Excellent job @suffolksmallholder , could you run us through the velux installation please , is it different to a tiled roof installation .

 

[suffolksmallholder]

Excellent job @suffolksmallholder , could you run us through the velux installation please , is it different to a tiled roof installation .

Velux windows have a selection of flashing kits to suit all roofing materials. There is a guide to these on their website, this is pictorial too just in case of language differences. So as an example; here in sunny Suffolk where there are a lot of pan tile roofs the wriggly tin and pan tile flashings are interchangable.
The actual windows themselves only fit one way and this is pretty clear on the instructions. There are tolerances but not much. Rafter spacing & nogs need to be correct and again there are dimensions for the spaces required for each frame size in the instructions. Careful cutting of your tin is paramount along with thought placing the frames and your original sizing. Don't forget to allow for insulation thickness and any timber you want to see in your finishes. Remembering that a minimum of 150mm is suitable in a roof to stop heat escaping. 100mm in between the rafters themselves and then anything from 50mm to 75mm fixed under these rafters to stop cold bridging then insilated plasterboard at either 27mm or 35mm overall.
Mine are the size they are because I wanted tham to fit perfectly in between the purlins in my timbered roof space giving that classic barn look. This was all considered in the design stage and the tin was cut by the suppliers to give a nice clean finish and this saved me a lot of time too.
SS

 

[designanddetail]

My little barn roof is covered with wriggly tin & there are four Velux windows fitted to the North elevation. There is 100mm of insulation between the 150mm rafters @ 400mm centres. All/any gaps are filled with foam to stop draughts. Tyvec is then laid tight over this & stapled followed by 175mm x 50mm treated battens @ 500mm centres. The wriggly tin is fixed in the usual way with self drilling screws although careful marking and a punch helped to start the holes. Pitch is 35 degrees.

Air flow is important both above and below the Tyvec. There are air holes drilled in the ridge-board and there are soffit vents too. All electricals are in a dedicated run under the Tyvec so I can have a clean view of the x 4 douglas fir trusses that I made a while ago. Careful attention was paid to the join of the cavity & roof insulation, again to stop any draughts.

When I finish inside there will be 180mm of insulation as I will fix 70mm to the underside of the rafters to stop cold bridging followed by insulation backed plasterboard then plaster. The walls are 350mm wide insulated cavity and I lead with the inner. ( blockwork goes up first) Not forgetting Flemish bond brickwork.
SS

Looks like a nice conversion. Credit to you.

 

[Poorbuthappy]

We used tile effect on our garage and office roof with anti condensation stuff on it. A frames and purlins. Just used plenty of rock wool in the loft space. But you do hear the heavy rain.

Quite like this -

 

[Tinman Steels Ltd]

A bit of a long story but one of my customers has been doing a roof on a conference centre, lucky for him his customer had sourced the sheeting from kingspan direct as it hasn't gone to plan.

The main issue they have is the rain noise (120mm Insulated) which i have never come across before as an issue as most industrial buildings tend to have internal offices so the noise isn't heard but it shows some times you can still hear the rain even with an insulated panel.

 

[rob1]

A bit of a long story but one of my customers has been doing a roof on a conference centre, lucky for him his customer had sourced the sheeting from kingspan direct as it hasn't gone to plan.

The main issue they have is the rain noise (120mm Insulated) which i have never come across before as an issue as most industrial buildings tend to have internal offices so the noise isn't heard but it shows some times you can still hear the rain even with an insulated panel.

just a thought but would the noise be less if the insulation is bonded to the sheet rather than it being separate ?

 

[Tinman Steels Ltd]

Sorry i never stated it is full sealed / bonded insulated panel from Kingspan, to be fair it hasn't gone to plan from the start as the sheeting should have been black on the underside and turned up white, all of the purlins had been punched with a 18mm hole and the cleats were 14mm holes. Lucky for my customer he had not sourced any of the products for this job as that could of been a head ache.

 

[S J H]

just a thought but would the noise be less if the insulation is bonded to the sheet rather than it being separate ?

I can't see noise being as much of a problem if it a standard sheet, then separate layers of insulation with an air gap in between. Noise is vibration after all

 

[Blue.]

Thanks for the ideas so far....

@elub what is the down side / catch to not getting a house passed under building regs?..... what happens when you want insurance?

It isn't a house so no building regs.

 

[tim@marford]

I can't see noise being as much of a problem if it a standard sheet, then separate layers of insulation with an air gap in between. Noise is vibration after all

Not read the full thread... I have several barns roofed with box section insulated steel sandwich. Rain is heard but not really an issue. The transition between bright sun and cloud gives loud thumps!

 

[Exfarmer]

You must have a very good layer of insulation , plus good ventilation under the sheet otherwise you are going to have very serious condensation under the tin and the battens will rot in a very short time

 

[joe soapy]

Neighbour built a garden shed, tin roof and polystyrene sheets under, had dreadful problems with condensation. has since glued polystyrene to underside of sheets and the drips have stopped.
So either bonded sheets or spray on foam insulation would be my guess

 

[Bruce Almighty]

This gives a good explanation about condensation & insulation.
My Mother's house built in 09/10 had TLX silver over the rafters with rock wool underneath. If we'd followed this guide we could've avoided having to staple a vapour barrier (sheet) between the rock wool & plasterboard to stop condensation

http://www.tlxinsulation.co.uk/asse...Guides/TLX-Silver-Install-Leaflet-2015.03.pdf