View Full Version : Driveway extension...6ft high wall.. questions.
08-06-2005, 07:06 PM
I went and looked at a job yesterday. The guy wants to extend his driveway. His driveway ends with a 2 ft high stone masonry wall. The customer wants to extend his driveway 15 feet out past his current wall. I would have to build walls on 3 sides of his current wall. The wall that would be 15 feet out from his current driveway would be 6 feet high. I built many walls, but never one so high where someone will be parking almost right on top off. I was figuring on 3 layers of geogrid. I also plan on backfilling the whole area with 3/4in crush stone, except for the top foot which i will use quarry proccess for a good base for pavement. The block being used will be Versa Lok.
Also the guys whole property slopes towards this one area. All the water runs this way. I figure i need also need to install a drain on the new driveway section.
What do you guys think about this job? This is a pretty big job for me. Besides the walls, i have to cut down trees, have the driveway paved, and build a guardrail. I hope this post makes some sorta of sense so i can get some advice out of you guys!
08-06-2005, 07:42 PM
Matt - I don't doubt your ability to complete this job, but there are alot of variables with this job that you may overlook. Definately get an engineer involved. When you are dealing with loads, hydrostatic pressures, and slopes it is better to have a higher entity tell you exactly how it is to be built. As long as you follow their installation guidelines, they will be held responsible for failures. Personally, I would think at 6' and bearing the load of a vehicle, 3 pulls of geogrid will not be enough.
08-06-2005, 07:54 PM
Listen to Chris, he is right. Involve an engineer. You are dealing with what sounds like a lot of back slope, probably toe slope, vehicular loads, drainage, guard rail and a six foot tall wall. An engineer is a no brainer.
There are many aspects of that job that you probably have no experience with. Have you ever installed guard rail directly behind a wall with grid? You can't just build the wall and drill for the posts. You will tear into the grid and make a mess. This is just one thing the engineer should be able to help with.
08-07-2005, 12:00 AM
I had a feeling i would have to go with an engineer. How do i go about this. I have to give the homeowner a estimate. So i talk to a engineer and get a rough $ range he will want to look at the job and add it on to my estimate or what? I may be young but i built alot of walls before, just none like this.
08-07-2005, 12:12 AM
Matt - You just have to explain to your customer that with the loads that this wall will bear and the complexity of the project itself, you must consult an engineer. Find a local engineering firm that has a good rep. Give them a call and explain your situation, at that point they may give you some info regarding their fees. Include them in your estimate w/ a unforseen circumstances clause stating some of the additional fees you may incurr. If your customer is serious abot the project he should have no problem waiting a couple more days.
Contact your block supplier as they often have engineering services available at decent prices and specific to their product.
08-11-2005, 05:15 PM
Make sure you get a site specific design and not a typical design. I don't know if a manufacturer will provide a site specific design for free. I doubt it. We pay $1200.00 for a site specific design on walls less than 3000 sq.ft. There is a big difference between a typical design and a site specific design.
Contact an engineer. Ask them their fees. Tell the client the fee (slightly marked up for your time) Explain to the customer that their is no way you can bid this project untill an engineer TELLS you how to build it. The engineered drawings will be the clients to keep if they chose to go with another contractor. If this is unaceptable to the client, walk away. Do not bid or do this job without an engineer.
08-14-2005, 01:37 AM
Once again, the key is SITE SPECIFIC. There are many typical cross sections of walls, etc. However, a SITE SPECIFIC drawing is exactly that. It takes into consideration toe slope, back slope, loads, etc. It is SPECIFIC to your project and the associated variables.
08-14-2005, 03:34 AM
You have what is called a live surcharge. In cases like that typically we tie both walls together with grid and lay the base across the grid. If you wee building it out of Keystone and had the stacking angle of the soil and a cohesion factor, I could plug it into Keygrid and tell you how to build it. I ran a basic drawing with a 30° stacking angle using Keystone Compacs (weighing 90 lbs each) and it showed a 6' layer of grid between course 1&2, then between 4&5, then between 7&8, and last, 10&11. This assumes you are installing 2 full embedment courses. I use this program to cross check engineers work, and for bidding before the engineer has a set of sheet available for me to see.
Since the wall is over 3' and has a live surcharge, the engineer will need a comprehensive soil study with a global stability analysis, and after he creates a set of working drawings you can then pull a permit. If you can't get a peorated drain into a pipe below grade, core a couple 4.5" diamter holes through the wall face at grade to drain it off. Also, when you compact the back fill, use a wacker or a pad foot roller and make sure you get 90 modified proctor scale as you install each layer of grid. The program also calls for Strata Grid 300.
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