Re roofing a carport.

[southeastpete]

Hi, I'd like to re roof out carport and thought I would ask the wealthy knowledge on here for advice again.

I'd like to totally do away with what is there currently. Mine and my neighbours carports fill the gap between our houses. Currently they both drain to the middle , then forward. Behind the carports, we both have concrete workshops. I like to span between the houses to make one long roof that drains to the front and back. I intend to span between the houses, with a support beam in the middle. I am planning on using 8x2 timber, 2.45m in length, with the total width 4.90m. So each timber will go from the house wall to the middle support post (4x4) where it will then be joined to the opposite timber with a fixing plate either side. I will then run 2x2 at right angles to these recessed into the 8x2's. Then on top corrugated plastic sheets.

My questions are, will this be strong enough to support someone working on top with crawling boards? Or could I go down to using 6x2 across? Also how far apart should I have the cross timbers? I was thinking every 1.5m? The length is 9m between the houses, then a further 5m over the concrete workshops.

Also, for water drainage there will need to be a gradient (1 in 60 I believe) should I cut angled notches in the 8x2's for the 2x2's or bolt the brackets for the 8x2's at a slight angle?

The roof will need to be able to take a bit of weight as I'm sure I will put storage shelves and hooks etc into it. Just trying to price it out before I propose it to the neighbour...

 

Thanks for any advice!

Edited April 3, 2015 by southeastpete

[blasterjudd]

Sounds a bit flimsy to me you possibly need to double up your timbers and have less than 1.5m between rafters.

Think about wind pressure too and any uplift will quickly pull out your fixings if they are wide spacings and damage the roof materials beyond repair.

If your in an exposed location then you should double up the rafter centres say at every 600mm centres and more robust fixings on the roof sheeting etc

I wouldn't go up on it without more rafters or a good supporting crawl board.

2 inch timbers will twist and crack so make sure you buy good quality timber?

Just a thought !

Happy roofing ..........

Edited April 3, 2015 by blasterjudd

[ladyjack]

use furrings to give your fall,also i would up the sizes of your timbers,600 ctrs for your joists

[southeastpete]

Really!? So are you guys saying an 8x2 every 600mm, or an 8x4!?

It's not exposed. What is there at the moment is 3x2 across at 2m spacings, with 2x2 across those every 800mm. That's been there for years, hasn't blown off, and I've even been on that with a crawl board to make a minor repair...

[Paddy Galore!]

if it's just for a roof cover then i'd go down to 6x2 every 1200, if it's supported in the middle. then 3x2 noggins @600 centres and furrins over the noggins for a ply lined roof, obviously this depends on the width of the sheet material you use. you don't need to recess the noggins into the main rafters, just nail tightly between.

[southeastpete]

What if it not ply lined, just the plastic sheets? It's mostly for cover, but will no doubt hang things from it like spare lengths of wood, baskets of vegetables, laundry. Also when I need to do repairs or anything, will need to be supported with a crawl board.

So I put the beam across straight and level, then put these furrins on top, which are angle cut wood right? What slope would I need on roof, I've now read people using 1 in 4, or 1 in 12! Far too steep for me. Will probably settle for about 1 in 30, so how would I go about getting furrins cut at that angle? (First time I've heard of furrins)

[southeastpete]

Here is a basic diagram of what I mean. The black lines are the area in question. The thick lines would be the 8x2's across betwee the houses. The thinner black lines the 3x2's running the length of the new roof. The corrugated plastic would run so the water drained to the back of the workshops.

 

Is this how the furrins would go?

[LowStandards]

My carport is 6m x 3m and I used 3*2 and I can dance on it!

[Paddy Galore!]

ahha! how big are the plastic sheets? you'll want to span at least 3 joists at approx. 1200 mm centres. furrin strips run across joists and looking at what you want they wouldn't do much good. suss out how many joists you need and fix them using straps at differing heights along the wall plate to create the fall, you won't need much more than a couple of inches for what is basically a flat roof.

[southeastpete]

Yea, so the top of the joists will be horizontal, and te 3x2's running across them will e at a slight angle. Do I just ignore the angle and screw them in, or put a slight angle on the joist?

Don't know the size of te plastic sheets yet, still looking. They are a lot more expensive than I though!

Edited April 3, 2015 by southeastpete

[vampire]

Just span across the width with the 8x2 joists with a fall to gutter,dont put firing bits in,just angle joists to be on slant so roof is at 90 degrees to it, then simply screw the metal channels going down the roof fixed into each joist,the twin wall roof sheets then sit into the rebate and the cap snaps in,screw through bottom of sheet in the middle to locate,tape top and bottom with foil tape,job done.

Your joists are plenty big enough for the span.

Have a look on roofing super store,they have everything you need once you have the joists in.

Edited April 3, 2015 by vampire

[southeastpete]

Your talking those flat plastic panels right? Box section? I'll look at those, was thinking the corrugated sheets though. It'll be whatever's cheapest tbh!

The lengthways struts would be to provide support more for when I'm on top.

Edited April 3, 2015 by southeastpete

[oliver90owner]

I sit here and think ''that could be a bad idea''

 

Only go ahead if you can answer all questions in the positive.

 

Will both neighbours be there for the duration?

 

What if either party wants to make alterations?

 

Who will be responsible for repairs?

 

Are there any insurance issues (third party)?

 

Where will the rainwater drain to?

 

 

Any change in the situation in the future may not be important and you may simply remove the structure if there were to be a change, but it may not be so easy if your neighbour is involved. Particularly a new neighbour.

[southeastpete]

At the moment both carports have roofs that span to the centre where there is a shared fence. All I am after doing is the same again, just a bit more substantial. There will still be a shared central fence, with beams from either house to centre. I would build it, offer the neighbour to have her son help if she wanted. Then after that, she would e responsible for her roof, me for mine, and shared for the central fence. And any future occupants the same. If any neighbour wanted to remove their side, they could. The structure would stand alone for either side.

Water would mostly drain to the rear. Which it mostly already does. We will each have a large water butt, and a soak away for excess further up the garden. I am currently thinking of having the front third of the new roof slope forward to reduce the amount of water going backward. This will drain away to the street, like some already does. Insurance issues would be no different to what is already in place. I am just changing an existing roof from pitching down into the centre to a gutter, to pitching rearward and using stronger beams.

[Alex C]

If you're fixing the sides of the roof to the side walls of yours and your neighbours houses, i would think very carefully about how you intend to stop the walls getting wet when it rains. If you get standing water trapped anywhere along those walls it will cause issues inside eventually. If this happens to the neighbours house, it could cause you a heap of issues.

 

I would look at installing some sort of flashing as even with a fall it could cause issues.

 

Stick some pics up before and after though. I like to see a good build thread.

[southeastpete]

Roger that. There is currently some sort of flashing tape, I will find something to do the job.

[Lord Geordie]

Best of luck matey! I am currently having to restore a canopy above my girlfriends front door. Took it off the wall to rebuild it, strengthened it and now need to try re felting and flashing it in. 4 wooden blocks to fit into soclets and then use wooden wedges to secure! Then fit the felt flashing. Not looking forward to it it's only 4 feet by 2 feet but never done anyrhing like this before. I can only imagine the work your going to have with such a huge span.

[Rst1990]

If you do use flash band use bitumen primer on the wall for good adhesion.

For a 5mtr span 6x2 will be good for corrugated roof or ply felt roof, 8x2 would be over kill for a roof area.

Also there is no need for cross rails, just use cut down 6x2 for noggins in between your joists. This will give you your strength so everything ties together as one unit and stops the timbers from twisting.

[bear-uk]

Try C&A Building plastics for your materials.

[vampire]

Kent building plastics

[southeastpete]

If you do use flash band use bitumen primer on the wall for good adhesion.

For a 5mtr span 6x2 will be good for corrugated roof or ply felt roof, 8x2 would be over kill for a roof area.

Also there is no need for cross rails, just use cut down 6x2 for noggins in between your joists. This will give you your strength so everything ties together as one unit and stops the timbers from twisting.

Thanks, that sounds like a good plan.

If you do use flash band use bitumen primer on the wall for good adhesion.

For a 5mtr span 6x2 will be good for corrugated roof or ply felt roof, 8x2 would be over kill for a roof area.

Also there is no need for cross rails, just use cut down 6x2 for noggins in between your joists. This will give you your strength so everything ties together as one unit and stops the timbers from twisting.

Thanks, that sounds like a good plan.

 

And I'll check both those sources for the bits cheers guys