How would you do it (Roof Pitch Adjustment) [TUTORIAL]

pmolson

ROOF PITCH ADJUST2.jpg ROOF PITCH ADJUST.skpHi,
I am wondering how some of you would go about changing the roof pitch on
the attached model.

It is currently a 10:12 pitch roof and I will be changing it to a 12:12 pitch.

The pitch needs to change without changing the overhang depth or the fascia height.

I am looking for clever, step saving Ideas to make this adjustment. I run
into this situation often, and I think I am not being as smart in my
technique as I would like to be. If there is something I can do early
on that will make adjustments later easier, I would love to hear those
ideas as well.

I basically just select each roof plane, make it a group, rotate it the degree
difference between pitches using the fascia to roof plane intersection
as my pivot and mend the roof manually with the line tool and inference
guides.

How would you do it?

p

Anssi

I would calculate the ratio needed, and scale the whole roof in the blue direction the required amount, and then correct the fascia heights afterwards.

Anssi

TIG

Make the whole roof one group above the fascia line.
Draw a long vertical line up from the fascia of the biggest roof outside of this and rotate it 45 degrees [==12:12].
Draw a line from its bottom end up the roof slope - inference Magenta = up-slope to the ridge.
Draw a vertical from the ridge to the 45 degree line and erase the unwanted bits - the vertical line represents the maximum extra height needed on the roof.
Select the roof group and Scale it using the top-center handle and snap to the top end of this temporary vertical line - the roof now has 12:12 slopes...

pmolson

Thanks, I knew you guys would have a trick.

I did as you said and it took all of 15 seconds to change all 10:12 pitches to 12:12.

Now just a little clean up on the intersecting different pitch shed roofs.

Thank you very much.

p

pmolson

Ok, I think I am dense.

I got the roof pitch adjustment trick. It's great.

Now I want to expand the entire peremiter of my soffit & fascia
from a 2'-1" overhang to a 2'-8" overhang.

I tried applying the same logic used to adjust the roof by:

make soffit & fascia a group.
determine scale factor (this is the thing I am getting wrong I think)
2'-8" divided by 2'-1" = 1.28 scale factor
use scale tool grabbing a corner "uniform scale by opposite points"
and enter 1.28

The result is a much larger adjustment than the 7" increase I am looking for.

What am I doing? What should I be doing? What is the meaning of life?

p

TIG

You want to make the whole roof-eaves bigger by 7"x2 [as the eaves get bigger in two directions] in both X & Y.
Make a Group of the horizontal eaves parts.
Place Guide-lines 7"x2=14" off one of the the X & Y sides each
Scale the Group in one axis at a time - so that it is increased up to these maker-clines.
It should now be the bigger size by 7" per side ?
If you Scale the whole roof by this 7" the pitch will no longer be 12:12 as the slope will be very slightly flatter...
Redo the vertical scaling trick on the sloping-roof parts group back to 45 degrees [12:12].
Projecting dormers etc will also scale disproportionately [aaargh]
It's probably be quicker to remake the parts right than it is to try and fix them ?

pmolson

Thanks TIG,

I reached the same conclusion shortly after asking the question.
I still made it harder than it had to be though.

I measured the full x and y distances of the whole group and divided those numbers into the full distances plus 14" to get a scale factor for the x & y and then scaled them independently.

Your more graphic method is much simpler.

The dormers are no big deal, I have a bunch of pre drawn dormer roofs with
different pitches and I will just plunk new ones in.

Thanks again.

p

TIG

Offset on the eave's soffit + pushpull would add 7" all round too...

pmolson

Yes, that is the most straight forward way to handle the soffit & fascia, but
bringing the roof perimeter out to the new fascia position is where the scale
group trick will come in handy.

p

pmolson

I was fooled,

I put horizontal x & y fascia parts into separate groups as you suggested and scaled
them independently to a reference line. The result was that the face that is in
line with the scale grip moved the correct distance but the other faces within
the group moved a lesser amount seemingly based on how far away they are from
the scale grip plane.

I may not be explaining this clearly and will try to give a visual latter.

I must make money right now and will have to re-visit this latter.

For the mean time what I will do is offset, pushpull the fascia and the
move each roof edge line individually letting it distort the roof pitch
and adjust the pitch after the fact.

Off to work.

p

TIG

In hindsight I recommend using Offset rather than Scale - then you can fix it at 7"+ ?