Replies

1. 
   MisterT | Dec 18, 2002 02:12pm | #1

   I was hoping this post was from one our fair sex posters.

   Do not try this at home!

   I am a trained professional!

1. 
   Newf | Dec 18, 2002 02:41pm | #2

   What kind of Fair has sex posters?Newf

   View Image

   Peace on Earth, Goodwill Towards Mankind

1. 
   MisterT | Dec 18, 2002 03:03pm | #3

   The BEST kind!!!

   TDo not try this at home!

   I am a trained professional!

2. 
   ian | Dec 18, 2002 03:37pm | #4

   Solo

   The problem you're trying to counter is the movement of the clay particles into the gravel.  Eventuall the gravel clogs up and ceases to drain.  How long it takes before the gravel is no longer free draining depends on the type of clay you have, your rainfall (including watering arround the house), and how coarse the gravel is.  Back when I was doing soil structures at uni the situation you're describing was stabilised using carefully graded layers of fine to coarse sand and fine gravel.  These days "that drain board stuff" or another goetextile does the job.  I cannot think of a situation where I wouldn't recommend its use.

   But hey, I'm an engineer who has specialised in road construction, we're generally into over kill where drainage is concerned.

1. 
   BernieSolo | Dec 19, 2002 01:49am | #6

   Thanks for the reply. To answer your question: "depends on the type of clay you have", our perk holes revealed "Blue Clay" as described by the county officer. Does this affect any of your recommendations?

   I would also like to know if you have any data showing how fast the fabric that encases the gravel can clog with silt? Common sense would seem to tell me that fabric would fail sooner than the gravel.(?)

   Now I think I know why the manufacturer of that drain board requires the top edge to be exposed at grade!--Solo

   Remember, measure twice... then keep cuttin'

   'til it fits really fine.

1. 
   ian | Dec 19, 2002 11:41am | #7

   Bernie

   I'm located in Australia so can't help much with identifying the properties of your "Blue Clay".  Others can advise you in better detail. 

   The principle behind using a filter is to prevent the soil or clay particles moving.  Briefly the science is: clay is fine - filter (gravel) is coarse - water and clay particles move through filter - clay deposits against structure and over time water builds up on wall. clay is fine - filter is not too coarse (ie it's the right specification geotextile) - water moves through filter, clay particles do not move, so over time water continues to drain away.It sounds as though the "drain board" manf intends that the material be periodicaly flushed out to remove fines. 

   ... Common sense would seem to tell me that fabric would fail sooner than the gravel...it depends on whether the fabric is correctly matched to the soil type.

   Have a look at this Dupont site:  http://www.geosynthetics-products.com/K_geotextile_fabric/geotextile_fabric_K1.htm  for a bit more information

   hope this helps, Dupond is not the only manufacturer.

   Ian

3. 
   Catskinner | Dec 18, 2002 05:05pm | #5

   If there's a realistic chance of water getting under your house, it's difficult to get to the "overkill" stage. Do whatever you need to do now, because it costs a real lot more to do later.

   As several others here have pointed out in other discussions, pay careful attention to surface drainage away from the house, too. Every now and then I have run into a tough surface drainage problem in gravel soils where you just know the surface water is going to be a problem when it sinks in. In these cases I use all the ususal subdrainage, then I drop the finish grade a foot, lay down a non-expansive clay cap about 6" deep, compact it, and put the surface soils back. So far it seems to be working real well.

   DRC

1. 
   BernieSolo | Dec 21, 2002 12:13pm | #8

   Thanks for the input. Please tell me what is "expansive clay".

   I'd also like to know if you use a special technique for compacting clay. I ask this because this "blue" clay that I have looks like broken rock when dug up. It seems like it would be similar to trying to compact field stone!--Solo

   Remember, measure twice... then keep cuttin'

   'til it fits really fine.

4. 
   RussellAssoc | Dec 21, 2002 08:21pm | #9

   There's no such thing as over-kill when it comes to drainage.  I didn't see where you mentioned drain tile with a sump, an absolute must.  Using your system plus drain tile should provide a system to outlive you and become a burden to your grown children - lifes best revenge.

1. 
   BernieSolo | Dec 22, 2002 06:19am | #10

   Hi Russ, thanks for checkin' in. Since you inquired about the drain tile, check out my full drainage description on an earlier thread:

   http://forums.taunton.com/tp-breaktime/messages?msg=25660.1

   Your opinion will be of great value to me.--Solo

   Remember, measure twice... then keep cuttin'

   'til it fits really fine.