House Excavation Boo – Boo
DEAR TIM: Enclosed is a set of my new home blueprints and some photographs. As you can see, I was supposed to have a ranch style home built with a walk out basement. Well, I do have a ranch house with a walk out basement, but the house is sitting two and one-half feet out of the ground. Now I need steps or steeply sloping sidewalks to get into and out of the house. The developer sold me the lot assuring me that it was a walk out lot. What went wrong? Why wasn't this mistake caught early in the job? What can be done? P. E.
DEAR P.E.: I've seen mistakes made before concerning foundation depths, however never have I seen a mistake as severe as yours. In fact, more often than not, house foundations are installed too deeply in the ground. Your house looks as if it has floated out of the ground.
Because I was not privy to your conversations with the lot salesperson, your architect and your builder, I am at a slight disadvantage. It is possible that all three individuals are partially responsible. However, the largest portion of the blame should be directed towards your architect and builder.
Walk out basements require a minimum change in topography in order to work. This calculation is really quite easy to do. Your plans clearly show that the height of your foundation was to be 7 feet 10 inches above the top of the footer. If you notice on the cross section portion of your blueprints, the architect has indicated that your basement floor is four inches thick and it rests upon the footer. Also note on the cross section where the soil at the highest part of your lot contacts the foundation. Using the scale on the drawings, it appears that only six inches of foundation was supposed to be visible above the ground at this point.
If you do the mathematics, you will see that you need a 7 foot change in elevation between where you walk out of the basement and the highest point of the lot where it comes into contact with the foundation. In your instance it appears that you only had a 5 foot change in elevation.
I noticed that your blueprints did not show a simple topographic map of the existing grade and proposed grade changes necessitated by construction activities. This, I feel, is the root of your problem. Quite possibly your architect failed to take a transit to your lot in order to determine just how much the lot sloped. Without this critical grade information, I don't see how it is possible to draw accurate plans.
Your builder also needs to answer some questions. Often, builders need to determine whether or not construction activities will create excess dirt. Sometimes this dirt can be distributed on the lot and sometimes it needs to be trucked away. This determination can usually only be accomplished by using a transit to determine the change of grade on the lot. Had your builder performed this exercise, the mistake might have been caught in the bidding phase.
Finally, prior to excavating, the house is accurately staked out by surveyors. The corners of the foundation can be easily determined. The excavator and the builder working together should have noticed the problem immediately. Even after digging the hole, the problem would have been evident, as the hole for the foundation would have only been approximately 5 - 6 feet deep. The fact that the foundation was subsequently poured indicates to me a lack of adequate job supervision. Had your builder been following the plans, he could have contacted the architect prior to pouring the foundation. At this point, you could have filled in the hole and sold the lot to someone who didn't want a walk out basement.
There is no easy solution to your problem. In order to achieve the look that is indicated on the plans, you need hundreds of cubic yards of extra dirt brought to your lot. Several retaining walls need to be constructed as well. None of this was indicated on the plans. This problem is a result of negligence or compounded mathematical errors on the part of the architect and builder. The extra cost to correct the problems should not be your responsibility.