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Garage roof
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Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 3:02 pm    Post subject: Garage roof Reply with quote
    

I'm trying to work out how a roof is constructed.

Walls are 4x2 timber framed, with 12mm ply on either side.

I'm going to get trusses made, but am unsure what goes between the trusses and the tiles.

Trusses held with purlins running the length, ply over these, then tar paper, and laths to pin tiles to?

If I want to insulate, a layer of insulation under the ply, held in pace with more ply?

This is only for a garage not a habitable place. Last roof was corrugated sheets nailed to purlins and was leaky and cold. But my thought seems to include a lot of ply.

Am I doing it wrong?

crofter



Joined: 11 Feb 2007
Posts: 2252

PostPosted: Fri Oct 12, 12 3:09 pm    Post subject: Reply with quote
    

I would build it, rafters (tied to frame with batt straps) then purlins then metal profile sheets, insulated if you wish eg https://www.rollaclad.com/insulated-box-profile-roofing-sheets.html No plywood required.

Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 3:33 pm    Post subject: Reply with quote
    

But they're so ugly. And our bedroom looks right out onto it. From her side.

vegplot



Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd
PostPosted: Fri Oct 12, 12 3:50 pm    Post subject: Re: Garage roof Reply with quote
    

Nick wrote:
I'm trying to work out how a roof is constructed.

Walls are 4x2 timber framed, with 12mm ply on either side.

I'm going to get trusses made, but am unsure what goes between the trusses and the tiles.

Trusses held with purlins running the length, ply over these, then tar paper, and laths to pin tiles to?

If I want to insulate, a layer of insulation under the ply, held in pace with more ply?

This is only for a garage not a habitable place. Last roof was corrugated sheets nailed to purlins and was leaky and cold. But my thought seems to include a lot of ply.

Am I doing it wrong?


Leave out the ply. Use Kingspan between the trusses for insulation

Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 6:15 pm    Post subject: Reply with quote
    

Paper pretty much hangs in the air, then? (If it wasn't for the king span)

T.G



Joined: 13 Sep 2009
Posts: 7280
Location: Somewhere you're not
PostPosted: Fri Oct 12, 12 6:39 pm    Post subject: Reply with quote
    

It may not need purlins depends on the size and I see no mention of a wall plate

Ty Gwyn



Joined: 22 Sep 2010
Posts: 4562
Location: Lampeter
PostPosted: Fri Oct 12, 12 7:04 pm    Post subject: Reply with quote
    

If the trusses are 3 3/4in x 1 1/2in approx,placed at 16in centre`s,you wont need purlins,they are just battened after felting,usually tack a batten underneath to stabilize,
These will sit on a wallplate on the forming.

Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 7:46 pm    Post subject: Reply with quote
    

T.G wrote:
It may not need purlins depends on the size and I see no mention of a wall plate


Nor doors, or windows. But they're there.

I only mentioned wall construction in case weight started to come into play.

Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 7:48 pm    Post subject: Reply with quote
    

Ty Gwyn wrote:
If the trusses are 3 3/4in x 1 1/2in approx,placed at 16in centre`s,you wont need purlins,they are just battened after felting,usually tack a batten underneath to stabilize,
These will sit on a wallplate on the forming.


Ta. Is 16 inch standard? The previous ones were nine feet apart! But only supported corrugated asbestos.

vegplot



Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd
PostPosted: Fri Oct 12, 12 8:03 pm    Post subject: Reply with quote
    

Nick wrote:
Paper pretty much hangs in the air, then? (If it wasn't for the king span)


Something like this...


Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 8:05 pm    Post subject: Reply with quote
    

Ta. That's a picture I was struggling to find.

It's a project that'll keep me busy for a day or three.

Ty Gwyn



Joined: 22 Sep 2010
Posts: 4562
Location: Lampeter
PostPosted: Fri Oct 12, 12 8:22 pm    Post subject: Reply with quote
    

[quote="Nick:

Ta. Is 16 inch standard? The previous ones were nine feet apart! But only supported corrugated asbestos.[/quote]

That was standard for a tiled roof construction when i last worked on site,1976,as underside of truss was ceiling,worked for 4ft plasterboard.

Presume your old trusses,spaced 9ft apart,were more like 6 x 3?

Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Fri Oct 12, 12 8:27 pm    Post subject: Reply with quote
    

No! Maybe four by two, if that.

I'm not convinced it was a quality construction.

T.G



Joined: 13 Sep 2009
Posts: 7280
Location: Somewhere you're not
PostPosted: Fri Oct 12, 12 9:11 pm    Post subject: Reply with quote
    

Nick wrote:
T.G wrote:
It may not need purlins depends on the size and I see no mention of a wall plate


Nor doors, or windows. But they're there.

I only mentioned wall construction in case weight started to come into play.


Ah, well I presumed correctly then I assumed they'd be included. Just surprised you mentioned purlins a timber framed garage.

Nick



Joined: 02 Nov 2004
Posts: 34535
Location: Hereford
PostPosted: Sat Oct 13, 12 9:36 am    Post subject: Reply with quote
    

Cos they're on the plans the surveyor drew up. Tbh, that's because they were in the original garage, and I guess required because there were so few trusses.

Another question, how much is a truss, any idea? Lets say 5.5m wide, and 1.6m high?

I've found some 99% perfect ones on eBay, for 300. For ten. Strikes me that's a bargain, no?

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