Advice on glasshouse roof design

[sebmaster]

Hello,

I want to build a small glasshouse and am trying to work out the roof but its being a bit of a pain, and I wondered if the pros here could cast their critical eyes over it.

The image below is what I have so far, but im wondering about the rafters that flank the valley.
At the moment I have the overhang on each equal to that of the common rafters at the ends on the same ridge, then Ive positioned them so that the top faces meet up, but what is the best way to do it?
Would it be better to join these together and then have the valley coming off this join?

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• sebmaster
• 3 Sep 2010
• 1

Thanks for any tips! Im having a suprisingly hard time trying to find examples of how a glass/poly roof like this is meant to be constructed.

 

[masona]

At the moment I have the overhang on each equal to that of the common rafters at the ends on the same ridge, then Ive positioned them so that the top faces meet up, but what is the best way to do it?

Sorry if it's me, not sure when the top faces meet up and the best way to do it

 

[sebmaster]

Hi masona,

Thanks for your reply (and apologies for my late one for some reason im not getting notifications anymore ). Sorry if my post wasn't clear, what I want to know really is how would you position the two common rafters that flank the valley given the roof in my picture?

At the moment I have it so that at the end of the rafters, at the tip of the overhang, the top of each is at the same level, but I doubt this is the best way for both looks and ease of installing the glass roof.

Its especially hard because the stone base is already constructed (not by me) and so nothing Quite lines up and the pitches are Slightly different.

If you were to remove the three rafters in my picture and design them again, how would you do it?

Thanks!

 

[^woody^]

Why don't you just set the rafters out from the gable to the required spacing, rather than artificially placing the two rafters either side of the hip and then having to infill the space either side of the them with unequally spaced rafters?

In the CAD program, copy the rafters as an array or suchlike to the required spacings, and then lay these out at right-angles to represent where the two roof planes join, and then insert the hip rafter by trimming the adjacent rafters to the line of the hip

The top edges of the hip rafter should be in line with the top edges of the other rafters on each roof plane, and the actual meeting point of the two roof planes is "inside" the hip rafter

 

[sebmaster]

Hi ^woody^,

Is this what you meant?

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• sebmaster
• 5 Sep 2010
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• sebmaster
• 5 Sep 2010
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• sebmaster
• 5 Sep 2010
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• sebmaster
• 5 Sep 2010
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(With the valley rafter still to be trimmed of course)

Thank you for your instructions, its looking much better already, my brain has been stalled at that point for days!

 

[masona]

I see if i can find a better diagram

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[^woody^]

It looks like the ridge level is set to the top point of the hip rafter and all the other rafters are at a lower level. Really all the rafters tips should come to one level, and this would mean that the top point of that hip is cut off horizontally - which may not suit the glazing.

The alternative is to design so that the roof planes meet at the centre of the hip and on its surface (not like I described previously). This means that the edges of the hip are set lower than other rafter edges and it is the centre line of the hip which lines through with other rafters and not the hip edges.

It really depends on what you are fixing on the top of the rafters/hip, as these will need to line through flush. So it may be easier to set up the actual plane of the finished glass level and work down from this, taking into account the glazing bar, and this will determine where the hip rafter comes to

 

[sebmaster]

Hi guys,

Yes the intermediate rafters are set at a lower level than the valley and the rafters at the gable ends by about 3cm.

Originally it was designed so that the panes would sit in from the top of the rafters with all rafters being the same height, but in this case of course there would be no draingage for the triangle panes flanking the valley rafter.
I then redesigned it so that the intermediate rafters would sit 1/3rd lower than the rafters at the gable ends, so the panes would join up over these and meet the other rafters at the edge 1/3rd in; but because of the slight difference in pitch between the main roof and gable on the porch I couldn't make everything line up to create a flat plane for the glass to lay.
(close up of the problem in my first post below)
(The rafters at the gable ends being higher than the intermediate ones is just for asthetics)

In the images in my previous post I avoided this by having the valley rafter at the same level as those at the gable ends so the panes meet it at the sides as opposed to meeting eachother on top of it.

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• sebmaster
• 5 Sep 2010
• 1

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• sebmaster
• 5 Sep 2010
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• sebmaster
• 5 Sep 2010
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Installing the roof is the next thing I need to read up on properly as i've never installed something like this before.
For where the glass meets the sides of the rafters my working plan was to build a simple wood frame which would sandwich the glass and sealant, with glazing bars attached to the lower rafters. But as I said I need to look in to this properly before the design is finished.

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• sebmaster
• 5 Sep 2010
• 1