# Velux windows on low pitch roof

#### SJRSJR

I'd like to install a Velux window in a ground floor roof, which requires a minimum 15 degrees pitch. How can I work out the pitch? I know you can also get a flat roof system but that will look unsightly. Thanks

do you remember doing trigonometry at school, particularly the bit about SOHCAHTOA?

noseall said:
do you remember doing trigonometry at school, particularly the bit about SOHCAHTOA?

Who was Sohcahtoa?

Was he related to Pythagoras?

^woody^ said:
noseall said:
do you remember doing trigonometry at school, particularly the bit about SOHCAHTOA?

Who was Sohcahtoa?

Was he related to Pythagoras?

i think he must have been

sin= opposite over hypotenuse

or you can do it by drawing and measurement if you prefer.

lol. That is some memory feat to remember.

I just about recall A Red Indian Thought He May Eat Toffees In Class - but can't remember if it was from maths or english lessons

3,4,5 seems to cover it all nowadays though

How I wish I could remember Pi

Yes, I remember Silly Old Harry Caught A Herring Trawling Off America.
Except I can't get my protractor or ruler through the plasterboard ceiling.

Does HSS hire theodolites?

You can get a rough idea of the pitch is to use a spirit level, put the spirit level on the roof and pack it out one end of the level until the bubble is in the middle then you may get a sliding bevel underneath the level then transfer onto the protracter

the roof is a big triangle. split the triangle in half at the ridge.

measure the upright distance (x)

measure the horizontal distance

x divided by y.

if the roof is less than 45 degrees you will end up with a number less than 1.

inverse or negative tangent (-tan) this number and it will give you your pitch in degrees.

^woody^ said:
lol. That is some memory feat to remember.
Maybe for some, but I seem to have a reason to use sohcahtoa at least once a week.

3,4,5 seems to cover it all nowadays though
That's only useful for confirming right-angles - no use when you're working out a fall, gradient, or many other problems...

Softus said:
3,4,5 seems to cover it all nowadays though
That's only useful for confirming right-angles - no use when you're working out a fall, gradient, or many other problems...

agree.

pythagarus's theory is useful for squaring up buildings, in other words finding out what the diagonal measurement is, armed only with the lengths of the two 'other' sides.

3 sq= 9
4sq = 16

16+9 = 25. sq root of 25 = 5

as Softus says, only useful with right angle triangles.

noseall said:
as woody says, only useful with right angle triangles.
Where did ^woody^ say that?

edited. sorry Softus.

are you aware your username is an anagram of tofu ss. sieg heil.

We were taught

Some Old Hags
Can And Have
Touched Our A*ses

Easy one to remember!

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