new homeconstruction with very poorly drained soil, HELP

[ttowne]

Hello All

In 3 weeks my log home kit will be ariving and I have some issues. Here are some facts regarding the land

1) 850'ele. ten acre lot that slopes 17'over 700 ft on slight hilltop in middle of nowhere, Mannsville NY(no zoning codes). The land then drops off quickly down to a creek basin 100 ft below the land.

2) soil type is a Ira series (IrB) which is suposed to be a gravelly silt loam,3 to 8 percent slope, very deep, moderatly well drained soil. I am not a soil expert but in my opinion the soil is "very poorly drained"

3) this spring has been very wet, after it rains the water comes up to within a couple of inches of the ground level in my test holes.

4) the soil only drains after 4-5 days of no rain and even then the wter level is only about 2.5 feet below ground level.

Can I build a foundation under these conditions if I perimiter drain the footer and french drain the land near the house to the road ditch??? If so can I run other lines into the main perimeter drain that will need to be 700' long to exit the field? Will all this ground water ruin my new home?? PULLING MY HAIR OUT
Thanks for any suggestions.
Tom

 

[Focht3]

You need a local consultant to help you - we can only do so much.

You used agricultural descriptions of the soil, not engineering ones - so my interpretation may be off. It sounds like you are dealing with a sandy silt or very sandy clay soil with gravel, and a shallow groundwater table. While you could try to drain the site, I think the best answer is to raise site grade by at least one foot, and preferably two. Depending on the site conditions and locally available materials, you could either import the fill from off-site or "borrow" it from another part of your 10 acre property. My guess is that importing fill is the better answer, but using on-site borrow material is cheaper.

What does your foundation design look like?

 

[ttowne]

Thanks focht3

The basement is a simple 28X36 precast from Jefferson concrete. The spec. sheet calls for a crushed 2 foot wide X 1 foot deep crushed stone footer tamped to 1in level. The concrete company then sets the walls. Thanks again.

 

[Focht3]

It sounds like you need to hire a contractor to put several feet of crushed rock fill on your pad site. The fill pad should extend at least 5 feet beyond the perimeter of the foundation, and then tapered at a 3:1 (H:V) slope to existing grade. It needs to be properly compacted. The real problem is that the building pad needs to be stripped first, then proofrolled to look for weak spots. Your wet site may show weak areas that will need to be removed and replaced, increasing your cost. But if you don't your log cabin may settle unevenly over time, causing doors to stick, unlevel floors, cracks in the walls, etc.

It's an economic decision. In any case I'd still hire a local consultant.

 

[Grouser]

ttowne
Remember that $500-$800 for the geotechnical engineer that seemed too expensive?
You have excluded significant facts that prevent remote analysis by the forum. Where is the house footprint relative to the lot boundaries and terrain slope? How deep is the basement? Will the basement have a concrete floor? How will the floor/wall joint be waterproofed? Are the water-filled test holes only near the proposed home site or are they all over the property? Do you know what the soil conditions are at and a few feet below your footing/basement elevation? Does the proposed home site appear to be in a residual valley or other notable geologic feature? Are there rock outcroppings on the property or in the local area? Would you be willing to move the home site to a less costly location on the property?

 

[SoilRocks]

Why pull all your hair out???

Take Focht3's advice and hire a local geotechnical engineer. He'll take all the information you've provided, and think of 50 things you haven't (see Grouser's notes above), and develop some recommendations to make your home a good one.

The ground water issue alone is significant enough to hire a consultant. In my experience, you should also talk to a waterproofer. A leaking basement is the worst, and not cheap to fix.

Be sure to set back that house from the slope you mentioned. Since you have the room, I would use a setback at least twice the height of the slope.

Good Luck!

 

[ttowne]

Grouser answers to your questions
1)House is basically in the middle and within 1 foot of the highest point of a gradually sloping ten acre lot.
2)the basement footer will be 1 ft of crushed stone 4ft below ground level.
3)the basement will have a concrete floor with 1ft of crushed stone underneath
4)Not sure of any waterproofing at floor wall joint but the basement will have a perimeter drain on both inside and outside of walls going to daylight
5)Water filled test holes are all over the property
6)As the hole has not been dug, I do not know the soil conditions below 5 ft deep but my 5 ft deep test hole is full of water (lots of rain in NY)
7)The home site is actually on top of a gradually sloping knoll that makes up the ten acre lot then drops off quickly 80-100 ft to small creeks on both sides
8)the only rock outcroppings are at the creek. There are shale walls in the creek basin that are around 60-80 ft lower than house site. So that is liklely the depth to bedrock but I am not sure??

There are other houses in the area, one is 400 ft away at the same elevation and they have minor problems with water seepage in their block wall basement this time of year. Mine will be solid pre-fab walls with wicking material and 1ft of stone surrounding the walls to ground level. Then that perimeter will be drained to daylight. Too late for engineer now as hole will be dug on Tue. Any last thoughts? Thanks to all for the info and support.

Tom

 

[Focht3]

Subfloor drains. You need them badly. Use at least 18 inches of washed concrete sand, put wrapped irrigation pipe about halfway down into the sand. Try to get a non-woven sleeve - they work a lot better. The woven ones clog over time - particularly in silty soils.

Make sure you have pipe at the perimeter as well as every 15 feet i.e. be sure that the maximum distance to a drain pipe is 7.5 feet or less for any point under the slab. This pipe will be laid essentially flat; be sure that the line outside the slab has at least a 2% slope to it.

Be sure that the subfloor sand and your premanufactured wall ("wick&quot drains are hydraulically connected. The discharge lines will need to be "critter proofed."

You've painted yourself into a corner...

 

[ttowne]

focht
Thanks. I understand the extra drains under the floor but why the sand?? Ok to have sand mixed in with the crushed stone that is to be under the floor of basement?? thanks.

 

[Focht3]

The sand acts as a filter for silt and clay sized particles. (Baby powder is actually silt and a little perfume; women's make-up is mostly clay.) If you don't get a really good blend of the sand and rock, bad things can happen. Better to go with pure concrete sand per ASTM C 33.

 

[Grouser]

Are you sure 4 feet depth of footing is deep enough to prevent frost heave beneath it? Check with local builders. Consider draining foundation into a gravel filled sump pit which then overflows to daylight or, put a heater wire like on the eave edge for roof ice dam prevention around or in the outlet section of the drain pipe to prevent freezing. See other frost heave related threads. You don't want the spring thaw/rains draining into a frozen pipe.
Find out how precast basement wall panels are joined. How are the joints sealed? Will the exterior thereof be waterproofed? With what? Will exterior gravel drain installation damage the waterproofing? Will builder warrant the installation? Use rigid foam insulation to protect waterproofing and keep basement warmer.
Be sure to slope the soil away from the basement walls to prevent water build up.
I agree your soil does not sound like it is 'free draining' but like Focht3 said, your description is an agricultural one.
Tell us what you found when the hole was dug. Dig small deeper hole off to one side to use as a sump to pump water out of the basement excavation.
Good Luck!