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DIY Forum >> Carpentry Questions >> Valley truss
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Message started by fred09 on Jun 7th, 2010, 6:02pm

Title: Valley truss
Post by fred09 on Jun 7th, 2010, 6:02pm

I have constructed a dormer window with the dormers roof angle matching the original roofs, namely 42degrees. When I cut the valley truss I thought I cut a 42 degree cut with a 45 degree bevel as it fits diagonally from the old roof to the new, but this doesn't fit. I had hoped to then fix 150x25 as the valley trough then lined with lead to give a good water seal. What am I doing wrong ??

Title: Re: Valley truss
Post by CWatters on Jun 7th, 2010, 6:13pm

Try a 48 cut on some scrap.

90-42=48

Title: Re: Valley truss
Post by fred09 on Jun 7th, 2010, 6:23pm

Tried a 48 but this didn't line up with the line of the dormers roof. Something weird going on for sure.

Title: Re: Valley truss
Post by Joiner on Jun 8th, 2010, 8:28am

Is it a ridge or eaves dormer?

Title: Re: Valley truss
Post by fred09 on Jun 11th, 2010, 9:35am

Sorry for the delay but I couldn't log in! My fault.........I think.
The dormer is on the eaves. Does this make a difference?

Title: Re: Valley truss
Post by Joiner on Jun 11th, 2010, 10:20am

Not really (they can also come off purlins), just needed to get my head around it, not helped by your reference to a "valley truss", by which I assume you mean the valley rafter?

Difficult to describe it all in words, so perhaps it might help if you take a look at this...

http://www.familyhandyman.com/DIY-Projects/Indoor-Projects/Attics/Attic-Remodeling/how-to-frame-a-gabled-dormer/Step-By-Step

It's a US site, but all the references are there and it gives an excellent step-by-step view of the different stages, including the laying out of the valley rafters.

Title: Re: Valley truss
Post by fred09 on Jun 11th, 2010, 12:03pm

Thanks for that JOINER - I seem to have a mental block on using the word rafter which obviously doesn't help when you're working on a roof!
I used a speed square to try and work it out but the valley/hip scale lines up with 15 when I measure the 42 degree of the roof pitch.  Trigonometry! Should have concentrated more at skool

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