Roof pitch calc. and culvert type/depth?

willy1947 · Jul 12, 2004

I need some help with two questions. First, my shelter house will have a 4/12 roof pitch and the shelter house will be 20' wide. How do I calculate the distance form the peak to wall? For instance I need to know how many perlins (sp) I need to run to be 2' on center.

Also, how deep should I bury a small (10") culvert, so that heavy trucks don't damage it.

Thanks,
Dave

tc35dforme · Jul 12, 2004

Assuming no overhang at the exterior wall, the measurement from the wall to the ridge should be about 10'-6" or so.

As for the burial depth of the culvert, what is the material ?? I think you also need to consider the grades and the gravity flow in the culvert ?? Can you add some more info ??

DiskDoctr · Jul 12, 2004

Dave,

To avoid calculations, take a piece of string and attach it to something. Measure out (level) 12', make a mark, then on that mark stand a 2x4 or something and measure up 4' and put a line on your upright. Make sure it is plumb with a level. (This gives you a 4/12 pitch)

Stretch your string from its original point to the line on your upright. Now, use your level to come back 2' horizontally(because 1/2 of your building is only 10', not 12') and mark the string with a marker where the level intersects it.

Now, just measure the length of your string and lay out whatever number of purlins you want. /forums/images/graemlins/grin.gif Also good for calculating roof area for shingles, trim, etc.

This little exercise is handy because you don't calculate anything (can be done onsite), and gives you an understanding of pitch (out 12, up 4), and helps you visualize your project.

Hope this helps.

-JC

PS- Don't forget to add on for your overhang...

TWINKLE_TOES · Jul 12, 2004

If you would like to calcualte:

The pitch is equal to the tangent of the angle to the horizontal. In your case of 4/12
An angle whose tangent is 4/12 or 0.33333 is 18.435 degrees. The length from the peak to wall is 10/ Cosine of 18.435 degrees or 10.541 feet. 10.541 feet is equal to 10 feet 6 1/2 inches. about 10'-6" or so.



I run dump trucks and cement trucks over Aluminum 12" culvert, 8" below grade backfilled with 5/8 crushed rock.

willy1947 · Jul 12, 2004

Culvert info.

In the field that my new driveway crosses, I have 2 wet areas. The ground is pretty much level though. So I thought I would stretch a small culvert from one side of the drive to the other to help drain this water. On the wet side I would dig out/grade the ground to help funnel the water to the culvert. On the dry side, it would actually come out of the hillside and drain towards the creek. I think there is enough slope to take care of the draining.

I saw an ad for the black corrugated pipe for culverts and thought about just getting something like that. My local trucking company suggested getting it and putting 4+ inches of gravel over it. Just wondering if everyone thought this would work. The water just puddles up in the driveway, because the ground is a little swampy here. There is an old base of #2 gravel that really helps too.

Thanks,
Dave

pekabu · Jul 12, 2004

I am not an expert. That said, I am making a driveway from the other side of my property and the road agent wanted a culvert there (12" min). I bought a 15" black corrugated because I don't want to clean it out. (Smooth inside, and bigger is better. Right?) Anyway, I asked the salesman about running dump trucks over and he said 10" of gravel and it will be fine. I needed 2' or so feet. Haven't done it yet, but it's on the list.

neilly2 · Jul 12, 2004

Not much to add, but a vote for the plastic pipe --- corrugated on the outside smooth on the inside. Manufactured by ADS, its tough and will never rust out.

http://www.ads-pipe.com/us/en/products/n12.shtml

rswyan · Jul 13, 2004

( My local trucking company suggested getting it and putting 4+ inches of gravel over it. )

I just installed a 12" steel culvert under the new driveway I'm putting in - the sales guy at Discount Drainage where I bought it recommended that it be buried at least 1' MINIMUM and the fill be well compacted if there was going to be anything of size (large trucks) run over it.

theonlybull · Jul 13, 2004

it's standard around here, for the amount of fill over the colvert, be equial to the diameter of the colvert.

johnday · Jul 13, 2004

Willy; Calculated Industries makes a Construction Master IV calculator that can be used for more than just roof pitch. It's also a regular calc. Never was good at fancy math, so I use mine quite a bit. I think they're around $75 and well worth it.