perlin question

[nikon70]

does the roof perlin need to be one length or can it be in a couple of lengths supported down with a 90 deg support? i am looing to do a loft space (not conversion) but the existing perlin is rotton

 

[noseall]

purlins can be joined usually with a scarf joint and a support below.

 

[nikon70]

thanks, does it have to be a certain ratio

2:1

or 8:1 ???

thanks

 

[noseall]

the span of any structural element, whether it is a steel beam a purlin a rafter or a joist will be governed by its size, the supports upon which it rests and its proximity to any other supporting elements.

in other words, a certain sized timber beam that is designed to span no more than eight feet will need a mid-span support should that same sized beam be required to span sixteen feet.

regardless of the above, any connections or joins in the purlin may need supporting.

 

[chappers]

As noseall said provided it is supported adequately it can be made of several pieces, providing you have suitable bearing for the supports necessary to support it.
If you can put in suitable supports you could use two completley seperate elements one immediately above the other providing they are set somewhere close to the position of the existing purlin.

 

[nikon70]

i intend to put a support on every rafter going across straight down to the loft floor joists from will this surfice? or should i replace the damaged perlin and support the perlin the same way?

 

[noseall]

you intend lending support to the rafters by using the loft ceiling joists!

the purlin will either need repairing or replacing or the rafters will have to be beefed up.

 

[masona]

nikon70 - can take a photo? Where about is it rotted?