Timber purlins

[956xl]

What size timber purlins for 20' bays

 

[miniconnect]

What size timber purlins for 20' bays

10 x 3 shed with exactly that going up at the moment.

 

[Dave6170]

9x3

 

[Pan mixer]

I have seen 9 x 3 bend after a while maybe 10 inch better.

 

[Sharpy]

At 4'6" purlin centres 9" by 3" stress tested.

 

[David.]

I am surprised you can find any timber good enough for 15ft, let alone 20...

 

[BredRedHfd]

Get a hold of Scandanavian if you can, putting some up presently. Cracking stuff
Got some been up 20 years, still straight as an arrow on 20' bays. Do not use English tanalised. Absolute carp

 

[agrotron]

Z purlins on 20ft

 

[Forever Fendt]

I am surprised you can find any timber good enough for 15ft, let alone 20...

Use C24 here now about £1.50 each extra but are far better and less rejected for use

 

[Cowcalf]

have 100k sq ft of sheds at 15 ft all on 8 x 2 timber purlins that have had 34 inches of snow on it with only a few giving way

 

[MD @Minshall Buildings]

I'm with Forever Fendt ...C24 worth the extra if you want timber, although most of our clients seem to be moving to steel Z's?

 

[Forever Fendt]

I'm with Forever Fendt ...C24 worth the extra if you want timber, although most of our clients seem to be moving to steel Z's?

Zed purlins can vary in quality of the tensile strength of the steel and the thickness of the galvanised cover, we very seldom use them on 15ft bays but always on 20ft

 

[MD @Minshall Buildings]

Interesting ...is this varying quality price driven?
The steel is pre galvanized in coil form, so the zinc thickness should be pretty consistent with the steel thickness as is a highly controlled galvanizing process?

 

[jimmer]

Was putting up a shed extension once with 40ft Zs on 20ft bays

 

[Forever Fendt]

Interesting ...is this varying quality price driven?
The steel is pre galvanized in coil form, so the zinc thickness should be pretty consistent with the steel thickness as is a highly controlled galvanizing process?

you can buy the slit coils that are used for rolling the zeds at various tensile strengths and different thickness of galv coating although it is the zinc that is alloyed to the surface that gives the rust protection and the extra coating is a sacrificial layer so the thicker the better

 

[MD @Minshall Buildings]

do you roll your own Zeds from slit coils then?

 

[upnortheast]

Our shed man reckons if you are using 9 x 3 on a 20ft bay then best use a decent sized steel as an eaves rail. Stops the timbers bending down the slope

 

[Forever Fendt]

do you roll your own Zeds from slit coils then?

no just doing some research into rolling galv gutters from 1.6mm and 2mm steel

 

[AndrewG]

I’ve a new shed here on 20ft 9x3s with fibre cement cladding and the timbers look terrible now the roofs on and they have obviously dried out. Any recommendations on where to get better purlins?