Pitched Porch Roof

C

cb9002

I'm building a porch and intend to cut a lean-to roof for it.

My porch will be 1.2m horizontally from the house to the wall plate with a 25 degree pitch, I was going to use 4x2 C16 rafters at 580mm spacings (four rafters along the width of the porch). Tiles will be Redland 49. According to the Redland website I'll have to use large (2x1) battens. I was planning on using the same 4x2 C16 for the ceiling joists.

Do those sound adequate?

Do I need any cross-bracing between rafters or joists?

Is it correct that the first and last rafters should be above the wall cavity?

I was going to cut the rafters 300mm or so oversize, then when they are all fixed work out the size of fascia and soffit I need.

My plan is to match the house by using the same (Redland 49) tiles, and building the gable ends up to the roofline. I believe I use fibre cement undercloak between the gable brickwork and the tile overhang?

This will be my first time building a roof and I may be back with more questions!

Thanks in advance
 
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Bespoke

Hi

Over the Christmas I will do you a general arrangement drawing. But down the centre of the ceiling joists I would put a line of noggins this will help prevent the ceiling joists from twisting, you can do the same on the roof rafters but I don’t think there is any need for the diagonal bracing.

You will find that Redland and companies like them will quote the higher numbers. Tiling battens come in two sizes 40 x 20mm and 50 x 25mm and the cost difference is pea nuts on your size of project so I would go for the 50 x 25.

Ceiling rafters 50 x 100 should be fine and the same goes for the roof rafters but you could consider 125 x 50.

Hears wishing you a very magical Christmas and a fantastic new year.
 
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[quote="cb9002";p="777220"
I was going to use 4x2 C16 rafters at 580mm spacings

4x2" will be ok but space them at 450mm centres.

Do I need any cross-bracing between rafters or joists?

no. but you will need a 5x2" bearer plate for the rafters and a 4x2" bearer plate for the joists, both will need bolting to the wall.

Is it correct that the first and last rafters should be above the wall cavity?

the end rafter usually finishes 2" inside the return wall allowing room for the end joist to sit along side the wall.

if you intend fitting barge boards then you will build in noggings which will then go on to support the end rafter. on a truss roof this is known as the ladder set.

I was going to cut the rafters 300mm or so oversize, then when they are all fixed work out the size of fascia and soffit I need.

good idea.

My plan is to match the house by using the same (Redland 49) tiles, and building the gable ends up to the roofline. I believe I use fibre cement undercloak between the gable brickwork and the tile overhang?

yes, use a 150mm cloak for the overhang. i hope the bricks will cut easily ;) p.s disregard my info' regarding the ladder rafter. ;)

This will be my first time building a roof and I may be back with more questions!

Thanks in advance[/quote]
 
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cb9002

OK, I'll use 4x2 at 450mm centres, will put the outer joists as you say Noseall.

Wallplate has been bedded in today, I'll try and get the bearer plates up tomorrow or Boxing Day.

Can you confirm that I skew nail the rafters into the bearer plates as I would into a ridge board and not birdsmouth them?

My plan was to use hangars for the ceiling joists on their bearer plate.

Cutting the bricks will be interesting as they're class II perforated engineers which tend to break at the holes. I'll grind as deep as I can with my 4 1/2" grinder!
 

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