How much slope/deflection is acceptable?

I first introduced my level to the manufactured housing industry. My home state of Kentucky was my first contact with state inspectors that actually checked for slope and had established that 1” variation was the acceptable margin of slope for that industry, in that state. This is 1” difference from the highest to the lowest point in the home. This was regardless of the length of the home.

In dealing with the other various industries the level has brought me in contact with this 1” standard is very tough to meet. What is much more reasonable would be a 2” variation from the highest to lowest reading, maximum variation over the entire house, with no more than ½ inch pitch per 10 foot span.

Now this does not mean that an 80 year old farm house that has settled to 3” should be torn down. However it should be noted that there is more than normal or unusual slope present, and this may impact the selling price of the home slightly. On the other hand, in a new 1.5 million dollar home, 2” variation would significantly affect the selling price if I were the buyer. First, if the floor or foundation is off 2”, everything sitting on top of that base structure is either off 2”, or has been modified to allow for this sloppy construction, (and I would consider this sloppy construction). If the contractor didn’t pay enough attention to detail to get closer to level with the very foundation, what else did he pass off as “good enough”?

As for someone using my level to perform home inspections, my advice would be to simply point out the variations, and be very careful about offering an opinion. If you do give your opinion be very sure to justify this as “just my opinion”. (Webster’s dictionary, opinion: a belief stronger than impression and less strong than positive knowledge.) Make sure your client understands the $100 to $200 dollar fee you charge for an elevation plot of the home is not paying for an expert engineering evaluation that will stand up in court. Your job is to simply advise the client of any elevation variations, and if a problem is indicated, there are engineers that provide expert testimony for a much greater price. It is up to your client to decide if further investigation is necessary.

So to recap, 1” or less is very sound, 1½ “ is pushing it a little, and at 2”, or more than ½” per 10’ span, I would document the elevation differences in my report, along with a notation that the client was advised accordingly.

Note:

  1. At the time of this writing there are no solid guidelines for acceptable and unacceptable slope specified by federal or state regulations for existing structures.
  2. An elevation survey is only one of several indications that structure or foundation problems exist.
  3. In most cases the inspector has no prior data to establish a benchmark or reference elevation.
  4. In some locations including Louisiana and older New England homes much larger deviation is the norm.