Roof pitch and size of soffit

[McBell]

Hi All,

Got a two storey extension in progress with a 22.5 degree pitch on the roof -required to ensure it does not go higher than the roof of the existing building. It's just occurred that the soffits will be much larger than the existing due to lower pitch. What is the best way of reducing the overhang?

 

[noseall]

Deeper fascia.

 

[Zeberdee]

Deeper fascia.

Simples

 

[^woody^]

How does a lower pitch = wider soffits?

 

[SurreyRoofingEstimator]

How does a lower pitch = wider soffits?

Seconded ?

 

[theoldun]

Hi All,

Got a two storey extension in progress with a 22.5 degree pitch on the roof -required to ensure it does not go higher than the roof of the existing building. It's just occurred that the soffits will be much larger than the existing due to lower pitch. What is the best way of reducing the overhang?

How does a lower pitch = wider soffits?

If you are working a lower pitch than existing and still keeping the same drop between top of plate and underside of soffit, then yes, your soffit will be wider, how ever it is not due to the pitch, but to the drop.
To reduce width of soffit, reduce depth of drop between top of plate and underside of soffit.
If you have a standard 2400 storey height and top of frames at 2100, giving a standard 300mm drop then run another one or two course of brickwork round external wall to reduce depth of drop and reduce width of soffit. We normally do this after pitching roof, and before facia cut to rafters. Some times we run a course of snapped headers round to give a feature.
oldun

 

[^woody^]

I don't understand any of that

The roof can pivot to any angle, and the soffit can be cut back to any width, and the fascia can be any depth.

From 45 to 12 degrees there is only a very slight [rotational] difference in the top point of any rafter in any case

If the OP can't get the fascia/soffit to line up, then the rafters must be sprung from the wrong height or wrong distance back on the wall

 

[theoldun]

What is the best way of reducing the overhang?


This is the question we tried to answer, but it appears to have got complicated so will try to explain in more detail.

. The roof can pivot to any angle, and the soffit can be cut back to any width, and the fascia can be any depth.

The roof can not pivot to any angle, as it has been designed, cut and formed to the angle of pitch as required. To obtain a level soffit, then width of soffit can only be increased by increasing depth of drop from underside of soffit to birds mouth seat cut or top of plate, what ever you like to call it. To decrease width of soffit, it is vice versa.

. 45 to 12 degrees there is only a very slight [rotational] difference in the top point of any rafter in any case

Whilst we appreciate that 12 degrees was only a matter of speech, we do not consider that a pitched roof. Instead we have used 45 to 15 degrees. That is a difference of 30 degrees. This a very large rotational difference. Example, if you place a 15 and 45 degree rafter on the same wall plate, the top of the 15 degree will be 20mm lower than the top of the 45deg at the heel cut line, however if you add on a 450mm overhang to the 15deg, the top of the 15deg will now be 160mm above the top of the 45deg at facia cut. Total 180mm difference.
For a 300mm cavity wall.
If you want an approx 200mm width soffit on a 15 degree pitch, then you will require a 450mm overhang and a 150mm drop.
If you want an approx 200mm width soffit on a 45 degree pitch, then you will require a 525mm overhang and a 375mm drop.
Just to confuse the issue, one other point to remember, on a 50x100 rafter on a 15 degree pitch the depth of the 75deg facia cut will be 105mm, whereas on a 45deg pitch the depth of the 45deg facia cut will be 141mm deep.
Trust this is now understandable.
oldun

 

[^woody^]

But the point is that the soffits don't have to be any different in width as the rafter tails can be cut to suit.

I can't work out how the OP is matching two roofs of different pitches in the first place, and being worried about the soffit widths. And if the roofs are not connected then the eaves detail can be still sorted out to be similar to the existing eaves dimensions

But it might require the wall plate height to be altered

 

[roofers]

the measurements are taken from on top of the roof. Simply mark a level at 12", hold it perfectly level and measure from the roof surface to your 12" mark, this will give you the rise. Be careful with this method as a roof with many layers of shingles, or any type of roofing that is irregular can give you less than precise results.