BenMiller
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| 09/26/2007 10:32 PM |
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I'm back for more until someone kicks me off of here.
I live in Southeast Iowa. Last year frost reached a depth of 50". I want to make sure my foundation drains well, so would like as much gravel over the form-a-drain as necessary, but learned today that frost penetrates gravel much easier than it penetrates soil.
What are you guys recommending for gravel backfill depth?
I promise I'll stop bugging y'all when I get above the foundation. Well, unless you're over on the SIP side of this forum too. (SIPs are scheduled for October 8 delivery)
Ben
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irnivek
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| 09/26/2007 10:51 PM |
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18 inches gravel is plenty with a filter cloth between gravel and non porous backfill material above.
Kevin |
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BenMiller
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| 09/26/2007 11:03 PM |
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Thanks Kevin,
I'm sitting on a clay hill, is it safe to call that non porous backfill?
Ben
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Mark Ross
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| 09/27/2007 12:05 AM |
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Ben:
For the presence of a frost heave to occure, there are two conditions that must be met. Freezing temperatures and water. Remove either, and frost is no issue. There is some latent loss under your footings from your basement slab, which will protect your footings. As for gravel allowing frost to move deeper into the ground, this is only conditional in locations where no ancillary heat from the surrounding soils will not be present.
Your fine with minimum gravel requirements and non porous fill as Kevin suggested, if your fill is porous with limited non porous cover, you could create a bathtub effect. Keep a slope on the grading so that water flows away from the building, and ensure that all downspouts have sufficent length to prevent flooding the wall and basement fill areas.
Mark Ross |
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walltech
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| 09/27/2007 7:18 AM |
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As stated above filtered tile at bottom of footing with 18" of stone coverage is fine, I would still cover stone with rosin paper and back fill with sand if available. To counter act the bathtub affect that Mark mentions cap the last 12" of your rough grade with your natural clay. This will slow the water penetration until it grades away at your required code slope.
Dave
p.s. From your pics on vertical subject your soil looks loamy, but hard to tell from a pic. |
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Mark Ross
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| 09/27/2007 9:57 AM |
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Dave, perfect description.
Ben, Daves dimensioned statements above are an ideal way to backfill, ensuring little hydrostatic pressue, and eliminates the bathtub effect.
Mark Ross |
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BenMiller
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| 09/27/2007 9:34 PM |
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Thanks for the info. The excavator showed up this afternoon and plans on backfilling Monday, I need to get my damproofing applied. I asked for 18-20" of gravel.
Sure do appreciate all the advice,
Ben
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irnivek
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| 09/28/2007 9:42 AM |
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I highly recommend running a plate compactor around the perimeter during backfill. With a touch of water if possible.
We see too many homes (with proper slope away from the home at time of home closing) which end up ponding water in flower beds and sidewalks sinking three years later.... |
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walltech
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| 09/28/2007 8:42 PM |
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Good point Kevin.
Dave |
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eric monkman
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| 09/29/2007 1:36 PM |
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Ben : If you are on a hill, as you say..can you connect your perimeter tile to a "daylight" drain ?
As noted above by Mr Ross, you will have no chance of frost damage if water is not present.
Clay soils can cause foundation problems due to their expansive nature, and poor draining ability.
Water is always the enemy. |
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BenMiller
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| 09/29/2007 11:53 PM |
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Eric,
I've got two drains running to daylight, I wanted these buried in 18" of gravel (to make a continuous gravel bed to daylight) but my excavating contractor blew that idea off. He thinks I must have a phobia of water as I've been interested from the beginning on how I was going to get the water away from my foundation. Just heard of another new home owner digging open their foundation after last weeks 2" of rain. I do not want to be that guy.
I do not have a sump pit, but all my tiles are connected to the daylight drain, and I will have a basement floor drain that runs through my septic system.
Ben
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icfblocks
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| 09/30/2007 11:39 AM |
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Ben,
A basement floor drain connected to a septic system can be a problem. That will be the "tattle tale" when you have a septic system problem. Also I hope you have a p-trap below otherwise sewer gas will enter your house through the drain. |
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Thanks,
Tom
www.advbuildingtech.com |
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eric monkman
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| 09/30/2007 4:08 PM |
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| Sounds like you have it well covered :-) Too bad about the excavator's brain power. |
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BenMiller
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| 09/30/2007 6:08 PM |
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Posted By irnivek on 09/28/2007 9:42 AM
I highly recommend running a plate compactor around the perimeter during backfill. With a touch of water if possible.
We see too many homes (with proper slope away from the home at time of home closing) which end up ponding water in flower beds and sidewalks sinking three years later.... Is there any concern running a with plate compactor if my walls were only poured last Wednesday? (They would only be 5 days old when I backfill. The floor system is on, no basement slab yet but there's 1/2" bar every 48" between footing and foundation.)
Ben
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eric monkman
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| 09/30/2007 6:21 PM |
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Ben: We re-inforce with approximately 1 1/2 to 2 lin ft of rebar per sq ft of wall area, below grade. Depends on height of backfill.
Re-inforcing schedules relative to wall height and backfill height are standards included in most manufacturers install manuals.
We are generally 6 in core however, and you may be 8 inches or more
We do not compact, but rather "top up" again later in the job. Safer. :-) |
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BenMiller
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| 10/01/2007 9:40 PM |
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Thanks Eric, I'd feel more comfortable with the "top up" method. Plus I think I'm getting on my excavator's nerves and I can just see the look on his face when I muscle a vibra plate into the overdig while he's backfilling. It may cause me to be a permanent fixture in the flower bed.
Ben
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Mark Ross
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| 10/15/2007 5:50 PM |
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Just make sure you have your floor box on for lateral support on the wall, otherwise they will flex in, and prefereably your basement drainage layer in and slab poured.
Just helps to prevent any movement.
Mark Ross |
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