Timber cutting angles

[sadsjon]

I have a triangular cross section roof at 45 degrees.

I have 90 degree turn in this roof over the front aspect of the house.

Internally, I therefore have timbers that are cut 45 degrees on one plane an then 45 degrees on another plane.

Does anyone have any idea how to work out the angles so that I can cut timer or insulation board to fit the voids.

WIthout trial an error I am never going to get the insulation fitted ...

I am sure there must be some rules of thumb that govern how to cut insulation and timbers to fit this setup.

If there are any roofers out there reading this they will know just what I mean ... I am sure :-)

cheers all,

jON

[sadsjon]

I have a triangular cross section roof at 45 degrees.

I have 90 degree turn in this roof over the front aspect of the house.

Internally, I therefore have timbers that are cut 45 degrees on one plane an then 45 degrees on another plane.

Does anyone have any idea how to work out the angles so that I can cut timer or insulation board to fit the voids.

WIthout trial an error I am never going to get the insulation fitted ...

I am sure there must be some rules of thumb that govern how to cut insulation and timbers to fit this setup.

If there are any roofers out there reading this they will know just what I mean ... I am sure :-)

cheers all,

jON

[Weatherlawyer]

I'm not sure they will.

If you could just post a couple of pics or a sketch it might help.

If you mean you don't know how to cut jack rafters that is fairly straight forwards. But I haven't a clue what you are talking about.

Anything on here suit your needs?

[sadsjon]

Sorry, its difficult to explain ... the reason I mention roofers is because, in my experience, good roofers are taught all about angles and how to cut timbers to make a roof.

At the join between the two roof's that are at 90 degrees to each other the gulley sits on a single timber that must be cut at 40 degrees on both planes to accomodate where the two roof's meet.

If I have a 4 x 2 and I cut a 45 degree mitre on the end, I then need to cut another 45 degree mitre ... so that this timber can sit flush against the wall plate.

where a straght rafter meets the wall plate timber the 4x2 is cut with a 45 degree mitre to sit flush against the wall plate timber .... where two roof's meet they must be cut at 45 degree on two planes ...

I can't sketch it because I am just as much rubbish at drawing as cutting timber :-)

Maybe I could take a picture ???

jON

[Alex]

I assume you mean a compound mitre,I also think you mean a carpenter not a roofer,they lay tiles

[Newshound]

Cutting timber to build this stuff, and getting it right first time, is what sorts the master carpenters from the rest. But for insulation board (I assume you mean celotex), just cut oversize and trim to fit.

[John Rumm]

Something like my picture here? :

Internally, I therefore have timbers that are cut 45 degrees on one

You mean where they join the gully beam running down from the apex of the roof (at G) to the wall plate?

In this case the ends of the beam would need to be cut with a compound mitre matching the slope angles a and b. Since in this case they are both 45 deg, your mitre angle will be 45/45

You just need to allow for the thickness of the insluation when measuring, otherwise you bits will come out too short.

You just need to keep the orientation of the panel or beam in mind and apply the same angles as used on the roof to it, in the same plane.