Shed roof dillema? with pic...

[seaco]

I have finally decided to extend my workshop it's 18'x12' all wood and I'm adding another section as in the pic 12'x6.6'...

The original workshop has a wooden tongue and groove roof with trusses about every 18" or so, I need to know how to join the two roofs together, the extension will simply but up but extending the roof and framing the cutout etc. is throwing me a bit, also would you use lead flashing in the gullies to make it water tight?

As you can probably tell this will be my first go at roofing and I probably could bodge my way through it but anyone with any ideas would be really appreciated...

 

[Shultzy]

Seaco, Its a girder and valley truss system that you need. Try here for ideas

http://www.cwc.ca/products/trusses/girder_system.php

and I'm off to bed now :lol:

 

[sigibbons]

Couple of lay boards and some valley jacks would join that fine imo.

 

[mel]

piece "o" cake :lol:
leave the original roof in and don't "cutout" as you say in your post
you will need to pick up the ends of the original joists as the support provided by the wall to be knocked out , will no longer be their .
in house construction , the first roof truss is doubled up , the truss nearest the truss ends provides support , ie truss hangars . for the original roof
i'm not sure that this is 100% nesasary as the new part of the building is only 6` 6" wide . but would be a nice addition
lay boards and lead flashing

good luck getting your head around all those angles :lol:

 

[ike]

Have you considered a single pitch roof on the extension?. It would be simpler.

 

[seaco]

Thanks for the replies I would like to cut out the roof Mel as I want as much space as possible, I'm not to up on the terminology of parts to a roof is there a site you know of that would show me what to do?

Shultzy the site you sent me to was just to complicated for my small brain... :roll:

One last thing does anyone know of a cheapish place to buy tongue and groove the the Somerset or the South West?

 

[Shultzy]

Don't do yourself down Seaco. I'll try and explain.

In the picture above only shows half a roof. A-A is the roof that's green in your picture
A-B is your new roof.

The roof over your extension is constructed the same as your existing roof.

Now the complicated bit

The new part of the roof that sits on your existing roof is made by constructing trusses that get smaller as they climb up the existing roof and are called valley trusses. The girder truss is just the truss that spans the opening you take out below to add the extension. If you try and do it as you have drawn, it requires complicated design and cutting of existing trusses. Hope this explains a little better.

 

[seaco]

Thanks Shultzy I see what you mean better now I was hoping I could have the roof join more open without to many trusses, but it seems not...

 

[seaco]

Would this kind of thing work, sorry about the rubbish use of Sketch-up ignore the joints etc. again due to my limited knowledge of said proggy, the basic idea would be to frame the cut out in say 100x50mm timber then build the trusses from there to keep as much head room as possible...

 

[mambo]

as for lead flashing

if your roof is currently felted all you need do is run a length of felt straight down the valley, leave at least a foot either side
then bring the roof felts over this into the valley and seal with tar or the joint sealant that comes in cault type tubes :wink:

 

[mel]

dont do it lee
theres nothing supporting the main roof by the last sketch up you posted
and theres nothing to stop the new extention walls pushing out either :shock:

are you serious ??????
or am i part of a wind up here :lol:

 

[Shultzy]

Seaco, what do your existing trusses look like?

 

[seaco]

Seaco, what do your existing trusses look like?

Shultzy I'll pop some pics on here tomorrow...

 

[Keith Smith]

This doesn't look too bad.

With the caveat that I really need to see the job in hand.

If the valley boards are run right to the ridge and are screwed to the existing roof with a collar fitted about half way up that should stabilise the existing shed roof, although it may need a ridge board fitting.


Then the far wall will need a serious wall plate extended across the existing wall, plus a 6x1 ridge board with simple A frame roof trusses in place of the rafters shown and maybe cross brace the cripple rafters which should be screwed to the valley boards.

I'm with mambo, no lead just felt, I'd run at least two layers down the valley it's a weak spot.

Keith

 

[seaco]

This is where the workshop extension is going...

This is the trusses in the workshop...

This is the area I want to remove...

 

[mambo]

i can see this isnt going to be as straight forward as it first appeared due to the shallow pitch of the roof and the design of the rafters :?

 

[engineer one]

lee how about taking a slightly different approach????

seems to me that what you are proposing will reduce the strength of the original, by basically removing the structural rigidity where that last but one roof truss is.

so why not have a lower height at that point, and bring the roof in below where the truss presently is.

or actually thinking about it at some length, i wonder whether the idea might be not to cut the original roof at all, but overlay it for that 4 feet or so with the extended roof of the extension, and lose the space for that small space. that would retain the strength of the original shed, and reduce the problems with water ingress, re felting etc. you would also be able to tie the longtitudinal to the original truss, thus supporting the extension end wall with the existing shed. cutting and patching always causes problems.

paul :wink:

 

[Inspector]

You could compromise a little by leaving the existing truss, top wall plate, and cross members in place and only take out the vertical board sheathing. It will give you some of the openness your looking for without a lot of head scratching.

When I look at your plans I have to wonder why you don't make it wider? If you extend to the edge of the existing door you will almost double the floor space. The windows and maybe the siding can be reused in the new wing. Your new roof would then have the same pitch as the original and the trusses can be copied. Then at least the effort to cut and redesign the old roof to be open to the new would have more merit.

Best of luck with the expansion.

 

[mel]

im racking my brains here :-k
trying to think how you can do it safely and cost effectively
structural strength is going to be the problem with the way you want to do it
:-k :-k :-k

 

[seaco]

Thanks for all the help everyone I think I may leave the cutout and just extend the roof across, as cutting it out seems to cause alot of problems?

Inspector, I can't really make the workshop any bigger as I'm taking up alot of the garden already, the pic shows the whole garden the shed on the right holds my wood, so the Wife thinks enough is enough so I've compromised on the size I've said...