Hello,
I am building an extension. I have no experience so am doing it from library books in my spare time. I would like some advice on the roof, as I would like to know which size rafters and ridge beam to use. I am on a shoe string budget so I would like to know the most suitable spec without going oversize.
I am asking advice because after consulting the trada tables, I was surprised that the clear spans seem quite short – according to the table I would have to have 47 x 195 rafters at 400mm centres (second edition page 39) but after looking at this forum, the most common size is 50x150mm rafters for extensions that can be bigger than mine.
The extension is single story with a dual pitch vaulted cut roof
the roof will have 4 velux windows (2 either side) width 550mm height 780mm
The roof pitch is 36 degrees
The span is 3360
The run is 1680
The tiles are concrete marley double roman
I live in suffolk (for snow loading)
The length from the existing outside wall to the far edge of the inner wall of the extension is 5040mm
Ideally I would like the roof to be open, with no rafter ties. I will put collar ties in 1/3rd down the rafters measured from the top of the ridge beam.
Originally I was thinking of placing the rafters at 600mm centres in order to fit the windows in without cutting the rafters, however after reading that it is more difficult to fit the tiles with the rafters at this width, I am considering either 400mm or 450 mm.
I think that these are the things I would like to know (though there may be other unknown unknowns):
Do I put the collar ties on every 2nd rafter?
Is it best to put the rafters at 400mm or 450mm, is it worth trying to put the rafters round the windows at 600mm, or is it better to keep the spacing completely even all the way along the roof. Do I have to double up the rafters round the windows, as I have read that this is unnecessary as the weight of the windows is less than the tiles anyway.
Which is the best value for money - a glulam beam or a flitch beam? (or is there another sort of beam that I have not considered).
The end wall of the existing building is not in great condition, but I have been told that I can bolt wall plates to the existing wall and fill drilled holes with epoxy resin. I know it is hard to tell without seeing the wall but does this sound like a satisfactory method to attach the ridge beam.
The ridge beam will rest at the other end on a steel plate on the new block wall . I am presuming that this steel plate just has to be a few centimetres wider than the ridge beam.
Thank you.
Any help would be appreciated,
Emma
I am building an extension. I have no experience so am doing it from library books in my spare time. I would like some advice on the roof, as I would like to know which size rafters and ridge beam to use. I am on a shoe string budget so I would like to know the most suitable spec without going oversize.
I am asking advice because after consulting the trada tables, I was surprised that the clear spans seem quite short – according to the table I would have to have 47 x 195 rafters at 400mm centres (second edition page 39) but after looking at this forum, the most common size is 50x150mm rafters for extensions that can be bigger than mine.
The extension is single story with a dual pitch vaulted cut roof
the roof will have 4 velux windows (2 either side) width 550mm height 780mm
The roof pitch is 36 degrees
The span is 3360
The run is 1680
The tiles are concrete marley double roman
I live in suffolk (for snow loading)
The length from the existing outside wall to the far edge of the inner wall of the extension is 5040mm
Ideally I would like the roof to be open, with no rafter ties. I will put collar ties in 1/3rd down the rafters measured from the top of the ridge beam.
Originally I was thinking of placing the rafters at 600mm centres in order to fit the windows in without cutting the rafters, however after reading that it is more difficult to fit the tiles with the rafters at this width, I am considering either 400mm or 450 mm.
I think that these are the things I would like to know (though there may be other unknown unknowns):
Do I put the collar ties on every 2nd rafter?
Is it best to put the rafters at 400mm or 450mm, is it worth trying to put the rafters round the windows at 600mm, or is it better to keep the spacing completely even all the way along the roof. Do I have to double up the rafters round the windows, as I have read that this is unnecessary as the weight of the windows is less than the tiles anyway.
Which is the best value for money - a glulam beam or a flitch beam? (or is there another sort of beam that I have not considered).
The end wall of the existing building is not in great condition, but I have been told that I can bolt wall plates to the existing wall and fill drilled holes with epoxy resin. I know it is hard to tell without seeing the wall but does this sound like a satisfactory method to attach the ridge beam.
The ridge beam will rest at the other end on a steel plate on the new block wall . I am presuming that this steel plate just has to be a few centimetres wider than the ridge beam.
Thank you.
Any help would be appreciated,
Emma