Thursday, December 31, 2009

Simple Grading Tips

I just want to say I hope everyone has a great New Years.!

I think one of the hardest area to grade is residential subdivision. Corridoring the street is easy but the lots have become cumbersome. The last two subdivision I have graded I was not able to use grading groups or corridors. All the lots were graded with feature lines. In addition, I had on average 20 retaining walls. Most subdivision grading design I have seen online, occur on flat surfaces where there are no retaining walls or swales between lots. With subdivision lot grading you have to take into account the max. slope front and back of lots, and grading around existing trees that are to be saved. With trees spread throughout your lot, it becomes more challenging. Sometime you have to create tree wells or blockouts to save the tree. On top of that, I lost count how many swales I had to create. Some techs and designers asked me why I didnt use subassemblies for the retaining walls and swales but that would only take more time and make the drawing twice as large. (Not good when its already 10 mb) Anyways here are a few tips I can give you about grading subdivisions.

1. Make sure all your breaklines are on the correct site
2. When grading the lots, dont grade the lots in one surface. Break them up into 3-5 areas then paste those
     surfaces into your PG.
3. Make edits to the surface definition to build a more accurate surface. For example, in the surface definition you can set max and min, elevations so any surface points below the min. and above the max. will be excluded from the surface. You can set the max. triangle lengths.
4. Look at the operation types in the surface definition and see what items need to be removed.
5. run audits to insure there are no errors in the surface.
6. Turn on your surface slope arrows to insure grades are correct.
7. To tie lots to back of walks along the street frontage you can extract featurelines from the corridor and add to the surface.
8. Minimize flat areas in surface edits
9. Simplify surface in surface edits
10. I would do your best to add names to your featureline that are added to surfaces.


  1. Great list.

    Grading object always seem to be the root of many crashes and corruptions. Thanks for the insight. I'm sharing this post with all my users. Maybe I can head off some problems before they start.

  2. Your welcome. What i would look for is crossing feature lines. Those always seem to crash or corrupt drawings. Thats why i turn on allow crossing feature line option.

  3. Hi. Greetings. This post is really good and blog is really interesting. It gives good details.
    Retaining Walls