Building on a "partial fill" lot

10 years ago

I've been reading some of the other posts on here but they have all been more severe than I think my land will be...

We are attempting to buy a lot in a subdivision in South Western PA, but we were told by the listing agent it is partial fill and we might want to reinforce the basement. It is slightly sloping downward and then gets steeper towards the back left corner of the lot (84x150 ft lot) We talked to the neighbor across the street and he told us basically they pushed the extra dirt from the other lots into our lot as the other houses were built. Our next door neighbor to the right needed two pilings in the back corner of the house and they are raised up a few feet higher than our lot. There is no one to the left.

My questions are basically what is the worst case scenario, how much is the most it could cost for pilings down to virgin earth? (We don't think it can be all that deep based on the natural shape of the land around). Also, who do we contact to get an evaluation of the site before we buy it? Is there any way to determine how many pilings before we buy?

Featured Answer

User

10 years ago

If you wish to consider buying this filled lot and building upon it you must do things the right way meaning you can't take short cuts in evaluations. There are some steps to the process.

1. Have your attorney prepare an option-to-purchase agreement for the property that gives you enough time to:

2.)Engage a professional for design of a preliminary floor plan(4-8 weeks).

3)Schedule a surveyor to stake the home's footprint (2 weeks).

4.)Engage a licensed professional geotechnical engineer to drill for soil borings and provide you with a report on how to construct the foundations (2-4 weeks) based upon your floor plan.

5.) Obtain an estimate from your builder (definitely needs to be a good builder with experience in these matters) for the extra cost of foundation and slab work in the home.

There are some things you need to make sure are included in the scope of the engineer's report. Any qualified engineer will provide recommendations about soils under footing areas. However, make sure they also address soil conditions under the basement and garage floor slabs as well as under the concrete drive area. I have seen these areas go unaddressed in reports, have no remedial action taken during initial construction, and be a problem with ground settlement years after construction is complete.

In my experience, one always negotiates for a reduction in the price of the property in these situations. The cost of these professionals can easily be in the range of $7,500. To this you add the additional cost of construction from your builder, and you arrive at a bottom line offer for the lot. Not knowing these extra costs precludes one from specifying an upfront offer for the lot cost in the agreement. The agreement simply gives you the exclusive right to purchase the property within a specified time period.

The option-to-purchase agreement is recommended if you are indeed responsible for all of the professional service costs. If you are responsible for all these costs you want the exclusive right to purchase the lot within the allotted time specified in your agreement. That said, I have seen developers, or the land seller, pay for the geotechnical engineering and survey work. In this case you might skip the attorney and purchase agreement and just perform the preliminary design.

Comments (8)

virgilcarter
10 years ago
You need to commission a soils engineer to take soils samples of your lot, where you envision you actual house to be, and to make recommendations for foundation design.

Worst that could happen: weight of finished house on uncompacted fill results in differential settlement of your standard foundation, with cracking and disruption of utilities and other built improvements.

Another important issue is the presence of subsurface aquifers and control of surface water runoff. Consistent moisture, over time, may lead to soil compaction, erosion and differential settlement throughout the property.

Use of piers or piles is only one possible foundation design. Another option is a concrete mat slab. Actual foundation design depends on soils investigation results and design recommendations.

Don't take this situation for granted. Do your due diligence.

Good luck on your project.
Annie Deighnaugh
10 years ago
Yow! Listen to VC! I remember an old architect buddy we knew many years ago and he always said, put your money underground. Skimp on this step only at your own peril.
nightowlrn
10 years ago
We came within inches of building on this lot .... knowing it was fill is why we didn't go through with building on it. Look at what happened to the eventual house owners

http://www.kgs.ku.edu/Publications/pic13/pic13_1.html
worthy
10 years ago
That collapse was the result of a landslide. Whole other worry!

There's nothing inherently wrong with building on fill. As long as you know in advance what you're dealing with. Much of the Toronto waterfront, for example, is built on fill.

Today: Note Toronto Harbour Commission Building, left of centre tower under construction.

In 1918, that same building dominated the harbour as it greeted cruise ship passengers docking nearby.

This post was edited by worthy on Sat, Feb 15, 14 at 21:05
renovator8
10 years ago
In the worst case you would need to take boring samples to determine the soil bearing capacity and if it is poor pilings or piers would be needed as well as structural beams connecting the caps.

If you hire a good geotechnical engineer the worst case should be an expensive foundation and perhaps a bit of foundation showing later if the grade drops.

I would expect to get a much better price for the lot than the earlier buyers did. If that is not the case move on.
nightowlrn
10 years ago
Ah Worthy - you are correct. I was thinking it was fill, but my husband just reminded me the soil person he hired said it was the rock and the cost of putting support in the ground that would have been more than we wanted to pay.
virgilcarter
10 years ago
There's a big, BIG difference between building on properly engineered and compacted fill and spoils simply dumped on a site and, perhaps, leveled with a dozer or grader.

Do your due diligence!