How to indicate roof design on site plan

[christillis]

Here's an odd one (hi everyone!), a planning consultant has asked me to show the roof pitches on a site plan, and I'm stumped.

 

Any ideas? This is what I've done so far:

 

 

Sorry to bother, any suggestions welcome! I'm so far thinking of showing a few basic cross sections on the same drawing sheet. This isn't a CAD technical thing, just a 'how to portray information' thing

 

Look forward to your comments

[ReMark]

I might have put a directional arrow with the actual roof pitch indicated above.

[Tyke]

One point comes to mind from your plan. Are your eaves and ridge heights the distances from the adjacent ground level to the eaves/ridges, or are they the distances above a level datum? I ask because some of the eaves heights on the same building are not the same, although with agricultural buildings that can be the case.

 

We always use heights above a datum and show some ground levels spread around the buildings. Some Planning Authorities do have their own queer ways of doing things and so what goes for one will not necessarily be the way another wants it doing.

[ReMark]

Why not just indicate the roof pitch instead of the heights? Adjacent ground levels would then be irrelevant.

[Tyke]

Why not just indicate the roof pitch instead of the heights? Adjacent ground levels would then be irrelevant.

 

The roof pitch(es) for symetrical and asymetrical rooves (with your arrow) would meet what the planning consultant asked for . I missed the point about asking for roof pitches and reacted on the information on the OPs drawing. My personal expeience with English Planners (including Consultants) is that what they ask for is not necessarily what they need. A roof pitch alone does not convey too much information, but the roof pitch, direction of fall and a height ties it down precisely.

[Dana W]

EDIT: I just went back and saw that you are in the U. K. My post is in inches but the premise is the same.

EDIT: I had the rise over run, should be fall over run.

 

Roof pitch is represented as the vertical fall over a horizontal run of 12". It is not relevant to the height over the ground.

 

Are you drawing the site plans as part of the architect's office or the civil engineer's office? If you are the civil engineer's office, don't calculate the roof pitch, copy it from the architect. It is his job, period.

 

If your approving agency has asked for the "Roof Pitch" in those very words then what you are showing is not correct.

 

The roof pitch is determined by the architect responsible for the design of the buildings. You need to find the pitch on the building plans and repeat those numbers exactly as those plans show it. You might only find the roof pitch shown on the side elevations and vertical sections. The pitch is usually shown on an elevation with a horizontally positioned right triangle, the angled line of which will run parallel to the roof line. The FALL dimension will be next to the vertically positioned base of the triangle, and the RUN dimension will be aligned on the horizontally positioned altitude line of the triangle.

 

Roof pitch is numerically representative of a ratio between the vertical fall over horizontal run. It has no relevance to the roof height above any point that is not on the actual roof surface.

 

For instance, the average residential roof in the U. S. falls 7" for every 12" of horizontal run. One does not normally see the pitch called out on a plan view of a building since that view does not visually show the pitch.

 

For these purposes I would show the above mentioned 7 in 12 pitch along an arrow (non angled leader) on the roof surface pointing away from the ridge, toward the eaves. The text over the arrow would be 7 in 12, and nothing more.

 

Roofs are actually (attempted to be) built to the pitch rather than the angle. Roof pitch varies by half inch increments here in the U. S.

Edited October 29, 2013 by Dana W

[Dana W]

Wait, I have a feeling that this is not a new structure since some of the roofs seem to be a little bendy. If not new, then you need to calculate the pitch ratio, probably the average pitch per surface, and call it out as fall over run, with the arrow as I stated.

[Tyke]

In the UK roof pitches are measured in degrees down from the horizontal. Just goes to show how things vary from country to country.

[christillis]

Hi ReMark, thanks for the prompt answer, much appreciated - I'll see if that satisfies the powers that be!

 

Hi Tyke, they are individual heights - I did want to use a datum, but the client didn't need the accuracy I would have preferred. You're right about queer ways with the PA's, it differs so much you end up doing most things 'just in case'.

 

Hi Dana W, thank you so much for an extensive response, it really is appreciated (as are all of your comments!). All of your comments are absolutely spot on, ignoring the imperial references of course. The drawings are primarily for planning purposes only to illustrate the existing site layout - the next job for me is to draw elevations of all of the barns (such fun with boring barns). The planning consultant just wanted a method of indicating roof pitch directions, even though buildings rarely have the lowest point in the centre!...oops, sorry, I mean 'center' :-)

 

It has to be said though, we do actually refer to the angle in degrees over on this island, as Tyke mentioned - but I do thoroughly appreciate your comments.

 

Thanks everyone, very useful indeed!

[Dana W]

In the UK roof pitches are measured in degrees down from the horizontal. Just goes to show how things vary from country to country.

Yep, I wonder how they call it out on the drawings, as in what is the symbology?

 

Pitched roof design came about in order to accommodate snow load. The flatter the roof, the sooner it collapses under the weight of the snow. Also, the steeper the roof, the more excess snow it will shed in extreme conditions.

 

Here in Florida, we worry about wind load and drainage, so our roof pitch rarely is steeper than 5/12, and you don't see many gable end roof designs here either. Almost all of them that are not totally flat are hip design so they resist side wind loads better in all directions.

[Dana W]

Hi ReMark, thanks for the prompt answer, much appreciated - I'll see if that satisfies the powers that be!

 

Hi Tyke, they are individual heights - I did want to use a datum, but the client didn't need the accuracy I would have preferred. You're right about queer ways with the PA's, it differs so much you end up doing most things 'just in case'.

 

Hi Dana W, thank you so much for an extensive response, it really is appreciated (as are all of your comments!). All of your comments are absolutely spot on, ignoring the imperial references of course. The drawings are primarily for planning purposes only to illustrate the existing site layout - the next job for me is to draw elevations of all of the barns (such fun with boring barns). The planning consultant just wanted a method of indicating roof pitch directions, even though buildings rarely have the lowest point in the centre!...oops, sorry, I mean 'center' :-)

 

It has to be said though, we do actually refer to the angle in degrees over on this island, as Tyke mentioned - but I do thoroughly appreciate your comments.

 

Thanks everyone, very useful indeed!

Well, I do tend to tell a person how to build a clock tower complete with giant bells and twirly bronze dancing statuary when they ask me for the time. Anyway, the concept is the same.

 

It's funny, but I used to work for a roof truss fabrication plant on the Eastern Shore of Maryland. There we had to draw the trusses by the degree of drop from horizontal of course, so the CNC saw could cut out the rafters and webs. The saw had no clue what drop and run meant. Some of the line workers had a different understanding of drop and run, they were on work release from Jessup Prison.

[Dana W]

In the UK roof pitches are measured in degrees down from the horizontal. Just goes to show how things vary from country to country.

Makes one wonder, after we put so much blood and tears into shedding the empire over this side, why we steadfasty hold on to the Imperial measurement system we inherited from the Empire, and still call it that.

[christillis]

That's interesting info Dana, thanks! Don't worry about the sucking eggs thing, we all do it from time to time

 

Hehe, that's really funny about Jessup Prison, I'm sure they're a pleasant lot to work with!

 

You're right about retaining the imperial system, I guess millimetres didn't exist when the Boston Tea Party occurred, otherwise they'd have gone as well as the British TAX's!

[eldon]

You're right about retaining the imperial system, I guess millimetres didn't exist when the Boston Tea Party occurred

 

On a historical note, the UK started to change to the metric system as a part of joining the European Economic Community. The conversion is not complete, nor is our desire to stay in the European Union (but that is politics)

[Tyke]

On a historical note, the UK started to change to the metric system as a part of joining the European Economic Community. The conversion is not complete, nor is our desire to stay in the European Union (but that is politics)

 

That's the official change over but the unofficial change over started in some industries much earlier. I worked for the National Coal Board as a mine surveyor and my old boss said the metric system was introduced there in 1947. But that didn't stop us working in imperial units and then converting it all to metric. We even used rods, perches and poles as units of measurement.

[christillis]

Hi again guys, here's something for you to be amused with. They were looking at an older version of the drawing, which was only an OS extract - so it didn't have any roof hatching...doh! As soon as I (re-)sent them the current version they were happy. Typical eh!

[Dana W]

You're right about retaining the imperial system, I guess millimetres didn't exist when the Boston Tea Party occurred, otherwise they'd have gone as well as the British TAX's!

They existed, it's just that the Puritans thought they were the devil's work.

[Dana W]

That's the official change over but the unofficial change over started in some industries much earlier. I worked for the National Coal Board as a mine surveyor and my old boss said the metric system was introduced there in 1947. But that didn't stop us working in imperial units and then converting it all to metric. We even used rods, perches and poles as units of measurement.

I owned a 2001 Dodge Dakota pickup that was assembled in Canada. It had a weird mix of metric and imperial fasteners.

[Tyke]

I owned a 2001 Dodge Dakota pickup that was assembled in Canada. It had a weird mix of metric and imperial fasteners.

 

I know the feeling. When I first came to Germany I bought a left hand drive Mini Cooper S and had no end of trouble when I took it to the workshop, they only had metric tools and the car needed imperial tools. Eventually I found a workshop with imperial tools and they were, fortunately, great at looking after Minis. Me? When it comes to car mechanics I have three left hands, even though I would love to tinker with cars. Give me a pencil and paper and a mathematical problem, then I'm your man.

[Dana W]

I know the feeling. When I first came to Germany I bought a left hand drive Mini Cooper S and had no end of trouble when I took it to the workshop, they only had metric tools and the car needed imperial tools. Eventually I found a workshop with imperial tools and they were, fortunately, great at looking after Minis. Me? When it comes to car mechanics I have three left hands, even though I would love to tinker with cars. Give me a pencil and paper and a mathematical problem, then I'm your man.

At least you have that extra hand for holding a mug of beer while tinkering. And now the new Mini is from Bravaria. It's probably assembled in Italy, France, Spain, Croatia, and Mindanao.