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Dealing with negative slope towards house  RSS feed

 
Tim Canton
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Hey all,

I am gonna try to explain this the best I can. House built in 1932. I live in the mountains so grading is a constant issue for alot of people. Single story 1000 sq ft house. I will describe this as if looking at the fron tof the house. the entire property is on a slope from back to front and the slope contuniues to go up forever. The back of the house sits at grade. Front sits about six foot above grade. Block wall basement, dirt floor.

Simultaneously the left side of my house sits on grade there is about 10ft out from there that is close to level and then it goes up and i mean probably 12 ft in 20 ft.

So i have this sort of combination slope to deal with, which in a sense is good because both on the side and the back I have one slope working with me, if that makes sense?

My big issue is what to do?? The basement is damp, I have some rotting sill plates that will get replaced later. Also the house never had gutters so that is obviously getting done asap.

SO any ideas on diverting the ground water?? ive thought about french drains but doesn't seem like the right fix. I was alos considering digging down say about 7 ft off the house to create a swale of sorts?? maybe line it and fill with gravel? I can not put any more dirt next to the house. it is on grade. so maybe build it up out from the house a little and grade down to the swale?

Any thought ideas criticisms etc will be appreciated.
 
David Biland
Posts: 45
Location: Southeastern USA - Zone 8
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I would try a nice deep swale with spillways on either side away from the house.  I would not put gravel in it.  If that does not work,  I would line the swale with bentonite clay.  If that does not work, I would grudgingly and carefully excavate and install a waterproof membrane below grade.  If that does not work,  I would curse the mountain to the end of my days.
 
Tim Canton
Posts: 175
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Compostme....what exactly do you mean by spill ways?  My only real way to get it away from the house totally is run the s wale past the front on the side and allow it to run off from there and similarly in the back I need to get it past the house.  Would you just re-seed the swale with grasses?

Also any ideas on how thw handle the area between the house and the swale?  Its at grade on that side so I cant build it up right against the house as you usually can.  Any ideas other than regrading 1000 sq ft area and removing alot of dirt?
 
Warren David
Posts: 187
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I take it that you really don't want much water getting into the ground around your house? I'm not sure if I can picture it all correctly but I was wondering if you can put in paving that can catch water and direct it away? I have done this in the past with paths and roads etc. Building a path with a tilt to one side will obviously collect water on that side and the whole path can gradually fall to direct the water to where you want it to go. The path doesn't really have to be used as a path. think of it as a drainage system that looks like a path.
 
David Biland
Posts: 45
Location: Southeastern USA - Zone 8
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I may not be visualizing this properly.  Take a look at this diagram and tell me if this is right.  Spillway may not be the best term,  water outlet?
swale.jpg
[Thumbnail for swale.jpg]
 
Warren David
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A swale could actually encourage more water into the ground behind the house. I think the water needs to be got out of the area as quickly as possible.
 
Tim Canton
Posts: 175
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First....yes that diagram is basically correct.    Minus the fact that i doubt they used a membrane in 1930.  So if from the diagram this is the front of the house imagine that you also have a slope coming towards you or towards the back of the house.  This is less steep than the side slope but slopes to the house nonetheless.

Warren...I can't really visualize exactly what you mean but i dont really like the idea of actual paving down the side of my house.  I think i may be misunderstanding you though.

The swale in the diagram is basically what I had thought...just on a smaller scope.  I was thinking about 2 shovel wide and maybe 10 inches down.  In this case the slope from the back helps because  its bringing all that water on the side downhill once i get it away from the house.

Warren..what concerns you about the swale causing more water?  I def do not want to do that.

I have thought about calling a grader to look at it but would much rather not spend alot to hire someone.

I appreciate you all and all your help.
 
Tim Canton
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oh yeah would pictures help?
 
David Biland
Posts: 45
Location: Southeastern USA - Zone 8
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Yes.  Pictures always help.  I think Warren is saying that the swale itself could become a collector of water which would slowly seep into the area below.  If the water was not readily shedding off this could be an issue.  I don't think it would make it worse, it would just not help the situation.  Preventing water from absorbing into the swale could be solved by lining it with clay or a membrane.  The picture I posted of the membrane was a suggestion of something you add to your foundation if nothing else works. 
 
Tim Canton
Posts: 175
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Here are some pics
the first is looking to the side from the back of house
the second is looking more to the back,  you can see the negative slope in 2 directions
pics 294.jpg
[Thumbnail for pics 294.jpg]
pics 295.jpg
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Tim Canton
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2 views from the major sloping side
pics 296.jpg
[Thumbnail for pics 296.jpg]
pics 297.jpg
[Thumbnail for pics 297.jpg]
 
Tim Canton
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one from more up front so you can see the continuation  and one from the back view to see it.  if you can visualize from the back shot the slope continues forward and to the left down to a mountain run off "stream"  and emptys across the street into a slightly larger runoff stream

I appreciate you guys
pics 298.jpg
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pics 300.jpg
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Brenda Groth
pollinator
Posts: 4434
Location: North Central Michigan
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my son's house sits on a slope with part heading toward the house and part heading away..

he put french drain in a gravel filled trench around the entire house having it leading to a drain away from the house..but he also has a sump pump in the basement in case any water does get in..generally there is no problem in his basement at all but it is there just in case..

the french drain system that he used is a perferated pipe with a sock over the pipe..a trench is dug and there is gravel in the bottom, then the pipe laid, and then more gravel and then soil over top (you can also use some hay or something to keep soil from sifting through the gravel like they do in drainfields)..

make sure there is enough slope to your pipes toward the draining area..you can bury that pipe to drain as far as you need to to get below your grade..they have connectors that are very simple to use
 
Tim Canton
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Brenda,

From what i understand real french drains are more for ground water issues than for surface water issues?  I could be wrong though.  I had posted this in the green building section also and had few responses.  If you wouldn't mind maybe you could post this on that one?  Maybe i should delete this one after that. 

i would like to hear more opinions on the french drains as well.  thanks
 
Warren David
Posts: 187
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compostme wrote:
I think Warren is saying that the swale itself could become a collector of water which would slowly seep into the area below.  
Correct. 
If the water was not readily shedding off this could be an issue.  I don't think it would make it worse, it would just not help the situation.
I think it would make it worse because swales are usually built to encourage water to go into the ground. If the op had asked for ways for more water to get into the ground then I have no doubt that somebody here would have suggested  a swale. To use a swale to take water away could be asking for trouble if the bottom of it is not completely waterproof.
If you are digging a shallow trench for the purpose of directing water away then it's really a ditch.
organick wrote:
Warren...I can't really visualize exactly what you mean but i dont really like the idea of actual paving down the side of my house.  I think i may be misunderstanding you though.
It's really quite simple. It's a path along the bottom of a slope. Rain runs down the slope, onto the path and then runs away along the path. Obviously the path would have to be built to just below ground level. If you don't want a path then that's fair enough.

If the water is already deep in the ground, well before it gets to your house then you probably need a deep trench around the affected sides of the house with some agricultural pipe at the bottom and filled with large gravel. It is better if you line the trench (or at least wrap the pipe)  with Geo Textile Fabric to save the pipe from silting up too quickly. The pipe will collect the water and take it away to an outfall, soakaway  or whatever you are going to use to either collect or dispose of the water. It's really very simple but it does involve some hard work if you are going to be doing it all by hand.
There are loads of sites with good explanations and diagrams.

I have worked on similar problems to yours. One of them was on a brand new house. The groundworkers had broken through an old land drainage pipe run when they dug the footings but  had not bothered to divert the drainage or lintel over it. Water was now running down the hill in the pipe, hitting the concrete footing and then spreading out along two sides of the footing. The ground for about a metre out on the two sides of the house was covered in algae.
 
Tim Canton
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warren could you point me to some info on that?    Thank you
 
Warren David
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This is a good one. I think you may need to go much deeper than the project shown on this site though. http://www.pavingexpert.com/drain16.htm
It really is quite simple.

Have you got any idea where you are going to send this water?
 
Tim Canton
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Thanks Warren,

I was getting confused by the wording.  To me that is basically a french drain system or slight variation of one correct?

Where the water goes??   I could basically daylight any buried drain in front of the house.  This would then run off towards the drainage running through the property.  I would rather it go into a pond but I dont have a very good area in the vicinity of where the water drain.
 
Warren David
Posts: 187
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Same thing. Where I am from we are used to just calling them land drains.

If you are going to be digging deep it may be a good idea to dig up against the side of the basement to expose the walls and waterproof them at the same time. The land drainage would then go in the trench as you backfill.
 
David Biland
Posts: 45
Location: Southeastern USA - Zone 8
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If the ground is already being saturated would it not just permeate under a drain unless that drain is at the footing?  That is a big job and you should definitely waterproof if you are going that far.

If you are going to be using heavy equipment, be very careful or hire a pro.  It is real easy to cause major damage to your foundation.  Here is a link for an example of a waterproofing.

http://www.metrowaterproofing.com/documents/BIT3000.PDF


I would try the simple stuff first.  Add your gutters. Dig a ditch.  It is possible that could be enough.

Erosion may be another issue in a ditch with a pitch so you would need to keep that in mind when designing it.



 
Tim Canton
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compostme.  I totally hear what you are saying about try simple first to see. I dont have huge problems so I am hoping guttters and surface water is all I need to deal with.  Also to begin with the house has been here 80 plus years and is doing ok sooo.  I had some people recommend a retaining wall but that seems intense to me.

The sloped ditch concerns me a bit with erosion if its just grass covered soil and especially across the gravel driveway.    Would a lined and gravel filled one hold up better?  of course than i have issues of silt clogging it.  ??

Thanks again
 
Brenda Groth
pollinator
Posts: 4434
Location: North Central Michigan
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well we have both here, we have ground water table very high, and we get a lot of surface water in the spring with snow melts or heavy thunder storms, esp when the ground is still frozen.

actually our french drains are put in fairly shallow, above the water table, to take water off the surface of the ground before it goes deep into the ground, away from buildings and in the direction we need it to go.

before the french drains were put in our propertry would be a mud pit for months in the spring..since the french drains we only have a few low spots that don't drain well..of course we also put in a large pond to gather the water that is draining off the property as well.

we have a large drainage ditch as well that drains the property into a swamp into our north woods from the french drains and pond overflow
 
Terri Matthews
Posts: 469
Location: Eastern Kansas
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Swales on the hillside to guide the runn off away from your house?
 
Tim Canton
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ok so i have had 4 people look at this.  2 said just regrade it with the low spot out towards the hill.

2 said french drain type setup.....




i like the idea of regrading it to avoid the issues with clogging drains etc but will it work  decisions...
 
                            
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Location: Colorado
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Hey Organick,

In the back gravel patio area, take up the gravel (for about 15 feet away from the house).  Grade the soil below at 2% (sloping away from the house).  Add a french drain system about 10' off the house and sloping toward the right (not left) side.  Respread the stockpiled gravel.  Areas like these should be fairly level, and the drainage occurs below the gravel and out of sight.

On the left side, where there is grass and less width to work with, also regrade away from house (at 2%) as far as practical, then transition back up the hill.  You might need to build a short rock wall in the really tight areas, but it doesn't look like you'd need to do that much from the pictures you've shown.  At the foot of the wall (or slope) would be a subtle, shallow grass-lined swale (and I don't mean a level one).  It should have at least a subtle slope from end to end, or it'll just turn into a mushy mess.  I also don't mean a ditch (something narrower and deeper), as remember, if it's grass you'll still need to get a mower on it from time to time, and you don't want to create a potential ankle-twister back there.  If you keep it wide and flat enough, and the grass is reasonably established (buy sod if in doubt), you shouldn't have any erosion problems.  I don't really know how severe the rain storms can be where you live, and how much runoff you get, so this is just a guess.

Also, install the rain gutters to keep that roof runoff away from the foundation, try to get the finish grade at the foundation wall down to 6" below the bottom of the sill plate (wherever possible), and install whatever moisture barrier you have the time and money for.
 
Heather Staas
Posts: 23
Location: Western MA, zone 5b
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Hmmm, I was thinking only "on contour" swales will stop and retain water, while a swale put in just off contour could be very effective at quickly moving water away instead. Or perhaps there is another word of "off contour swale" like a diversion ditch or something? Still absorbing the vocabulary, sorry. But very interesting as I'm looking a house and property with a similar problem, only less pronounced.
 
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