Dairy building 20ft bays. Wooden or steel purlins?

[stablegirl]

Getting mixed messages on this.

It's for a dairy cubicle shed, no side cladding 16ft to eaves open protected ridge 22 degree roof pitch.

Do I have wood that may sag or steel that may rust?

 

[Headless chicken]

15ft bays and wood is what we went after being told in no uncertain terms z purlins will rust

 

[Blue.]

I've 20' bays on my 115' wide 17.5degree pitch cubicle building,the timbers have never bowed at all.

The secret is using seasoned timber,I left mine near 12months in a dry airy shed before I used them (despite arriving dry)

Another way is using a angle stay from the rafter lessening the span in effect.

 

[Scholsey]

Getting mixed messages on this.

It's for a dairy cubicle shed, no side cladding 16ft to eaves open protected ridge 22 degree roof pitch.

Do I have wood that may sag or steel that may rust?

Got similar dimensions to you including the pitch room with Z's and so far so good but it has only been up 2 years.

 

[SimonB]

If you would like advise please call us on 01270 781158.

 

[Fraserb]

Our oldest cubicle and with z's is 22 years old and so far so good with no signs of rust

 

[upnortheast]

Timber purlins (9 x3 ) on 20 ft bays here. Asked the question when the shed man quoted for them. A steel eaves beam stops them sagging - Not sure what size it is - edit 9x5 RSJ

 

[Northeastfarmer]

Z purlins every time

 

[roscoe erf]

Timber here no sagging yet

 

[agrotron]

I have just gone through the same problem. Asked many different people and got different opinions. I have chosen z purlins as my personal experience with wood is that it does move and twist.

 

[Forever Fendt]

If you would like advise please call us on 01270 781158.

Can you not put the advice on here for us all to see rather than the op having to call you

 

[Hesston4860s]

Z purlins every time. Just put a lean too up for a chap with timber and it was banana shaped before we started, makes roofing it a night mare !.

 

[Tinman Steels Ltd]

There is nothing wrong with using either a timber or steel Z-purlin as it is down to preference but it is recommended to use a barrier tape between the purlin and the underside of the sheeting if tanalised timber is used.

 

[Forever Fendt]

There is nothing wrong with using either a timber or stee Z-purlin as it is down to preference but it is recommended to use a barrier tape between the purlin and the underside of the sheeting if tanalised timber is used.

does that still matter now the treatment does not contain CCA

 

[Tinman Steels Ltd]

It is a difficult one to say for sure but it is classed as best practice, if you look at most traditional tiled roofs it tends to be the fixing that fails more than the lath and this is normally down to corrosion.

When you look at the price of a barrier tape even if you use a standard pvc tape it only works out about £0.12 per linear metre for a 50mm x 33mtr roll.

 

[stablegirl]

So we haven't come to a definitive answer to this?

It will be open on both sides and have a open protected ridge so it should be airey and not a lot of condensation? This should help z's?

 

[Forever Fendt]

So we haven't come to a definitive answer to this?

It will be open on both sides and have a open protected ridge so it should be airey and not a lot of condensation? This should help z's?

Zeds then if its so open,use a good gauge and they will last a lot longer if corrosion does become a problem,also see if you can use stainless fixings if its big 6

 

[Headless chicken]

So we haven't come to a definitive answer to this?

It will be open on both sides and have a open protected ridge so it should be airey and not a lot of condensation? This should help z's?

But you want stack effect with the warm air going up. The warm air is going to condense on the z's

 

[bigw]

I would put timber purlins as the z's will rust over time. If you are worried about purlins sagging then get the cleats made larger to help span the weight either that or go to 15ft. Where will you get your kit from @stablegirl

 

[stablegirl]

Possibly a local lad, ive has quite a lot of quotes.