Car Port

Section62

the_lunatic_is_in_my_head said:

Do you have a link to an example by any chance please?

Google is throwing up lot of standard roofing membrane and a lot of results for the metal roofing with this already applied but not having much luck finding the right thing. 

You just specify 'Anti-Con' when ordering the sheets - the material is bonded onto the sheets either in the factory or mill.  I'm not aware of it being sold for retrofit, but you might find someone willing to sell a small quantity retail.  It wouldn't make sense to buy and apply your own if you are buying the steel sheets - the factory will be able to do a much better bonding job than any DIY method.

As an example (not a recommendation) -

https://www.steelroofsheets.co.uk/anti-condensation-liner/

the_lunatic_is_in_my_head

Section62 said:

the_lunatic_is_in_my_head said:

Do you have a link to an example by any chance please?

Google is throwing up lot of standard roofing membrane and a lot of results for the metal roofing with this already applied but not having much luck finding the right thing. 

You just specify 'Anti-Con' when ordering the sheets - the material is bonded onto the sheets either in the factory or mill.  I'm not aware of it being sold for retrofit, but you might find someone willing to sell a small quantity retail.  It wouldn't make sense to buy and apply your own if you are buying the steel sheets - the factory will be able to do a much better bonding job than any DIY method.

As an example (not a recommendation) -

https://www.steelroofsheets.co.uk/anti-condensation-liner/

Thank you again Sorry I thought you meant you can buy a roll of it to install yourself under/between rafters rather than already applied. Most of the places I looked at offered the option of the anti condensation coating so will go with that if we go with the metal.

Section62

the_lunatic_is_in_my_head said:

Section62 said:

the_lunatic_is_in_my_head said:

Do you have a link to an example by any chance please?

Google is throwing up lot of standard roofing membrane and a lot of results for the metal roofing with this already applied but not having much luck finding the right thing. 

You just specify 'Anti-Con' when ordering the sheets - the material is bonded onto the sheets either in the factory or mill.  I'm not aware of it being sold for retrofit, but you might find someone willing to sell a small quantity retail.  It wouldn't make sense to buy and apply your own if you are buying the steel sheets - the factory will be able to do a much better bonding job than any DIY method.

As an example (not a recommendation) -

https://www.steelroofsheets.co.uk/anti-condensation-liner/

Thank you again Sorry I thought you meant you can buy a roll of it to install yourself under/between rafters rather than already applied. Most of the places I looked at offered the option of the anti condensation coating so will go with that if we go with the metal.

This is likely to be the easiest and lowest-maintenance solution if the building is open to the elements and doesn't need thermal insulation.

If you go for a profile with a 'flat' trough (e.g. 'Box profile') then you fix them through the flats using "sheet to timber screws" with an EDPM washer.

e.g.  https://www.toolstation.com/techfast-sheet-to-timber-hexwasher-roof-screw/p46781

These are usually 'self-drilling' - but you can get a better result if you make a small pilot hole first.  It is also a good idea to clean up the drill swarf as you go - it has sharp edges and if you walk on it there's a risk of pressing it into the plastic/paint coating which will shorten the sheet's life. (wearing clean footwear is also important for the same reason)

You might also want to check with the sheet supplier if they can do galvanised steel 'Z-purlins'.  For longer spans these can be cheaper (overall) than timber.  In which case you'd use "sheet to metal" fixings instead.

the_lunatic_is_in_my_head

Section62 said:

This is likely to be the easiest and lowest-maintenance solution if the building is open to the elements and doesn't need thermal insulation.

If you go for a profile with a 'flat' trough (e.g. 'Box profile') then you fix them through the flats using "sheet to timber screws" with an EDPM washer.

e.g.  https://www.toolstation.com/techfast-sheet-to-timber-hexwasher-roof-screw/p46781

These are usually 'self-drilling' - but you can get a better result if you make a small pilot hole first.  It is also a good idea to clean up the drill swarf as you go - it has sharp edges and if you walk on it there's a risk of pressing it into the plastic/paint coating which will shorten the sheet's life. (wearing clean footwear is also important for the same reason)

You might also want to check with the sheet supplier if they can do galvanised steel 'Z-purlins'.  For longer spans these can be cheaper (overall) than timber.  In which case you'd use "sheet to metal" fixings instead.

Thank you again, very helpful  

We used some metal stud work indoors for an area behind a stove and I was surprised by how affordable it was, I think it workout out cheaper or on par with timber and the install was far easier than building a timber stud frame.  

One of the roofing sheet suppliers has this on their site, as you say overall might work out better all round. 

Section62

the_lunatic_is_in_my_head said:

Section62 said:

This is likely to be the easiest and lowest-maintenance solution if the building is open to the elements and doesn't need thermal insulation.

If you go for a profile with a 'flat' trough (e.g. 'Box profile') then you fix them through the flats using "sheet to timber screws" with an EDPM washer.

e.g.  https://www.toolstation.com/techfast-sheet-to-timber-hexwasher-roof-screw/p46781

These are usually 'self-drilling' - but you can get a better result if you make a small pilot hole first.  It is also a good idea to clean up the drill swarf as you go - it has sharp edges and if you walk on it there's a risk of pressing it into the plastic/paint coating which will shorten the sheet's life. (wearing clean footwear is also important for the same reason)

You might also want to check with the sheet supplier if they can do galvanised steel 'Z-purlins'.  For longer spans these can be cheaper (overall) than timber.  In which case you'd use "sheet to metal" fixings instead.

Thank you again, very helpful  

We used some metal stud work indoors for an area behind a stove and I was surprised by how affordable it was, I think it workout out cheaper or on par with timber and the install was far easier than building a timber stud frame.  

One of the roofing sheet suppliers has this on their site, as you say overall might work out better all round. 

The other advantage of Z-purlins for longer spans is that you can typically achieve the span with a shallower (less tall) member - which is useful of you are tight on permitted development eaves/total height, or you want a really long span to have a clear floor below.  E.g. for a double car port there's a lot of advantages in having no supports in the middle.  6 or 7m clear span should be achievable with a Z-purlin of about 150mm depth.

Note that if you use steel sheets they are fitted to 'purlins' (at right-angles to the slope) and not 'rafters' which would run in-line with the slope. So if you want the roof to slope front to back then you use purlins that run side-to-side.  These would be supported by the side structure(s) - allowing the front to be completely unobstructed and the back only needing enough structure to give the sides sufficient lateral support (aka bracing/proping).

On commercial structures you should use 'anti-sag' bars between the purlins, but for a DIY project the same effect could be achieved by using 6x2 noggings - these would also act as spacers to keep the purlins parallel, which is important when it comes to screwing the sheets down.

This does mean you can achieve a fairly lightweight roof structure - the flipside of which is still needing to make sure the roof is securely attached to the support posts/walls, and in turn to the ground.