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Shedding rainwater away from foundations  RSS feed

 
Ionel Catanescu
Posts: 174
Location: Timisoara, Romania, 45N, 21E, Z6-7
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Hello everyone.

Water going into foundations can cause big problems if you have expansive soils or freeze/ thaw cycles.
In my neck of the woods, the panacea for this is to pour a concrete pavement (sidewalk) around the foundation about 3ft/1m wide and 4in/10cm thick.
This sits on top of a gravel layer with the same size.
The concrete is above grade, sloped about 3% away from the foundation.
The joint between foundation wall and pavement is filled with bitumen to ensure an elastic seal.

ProsCons
sheds water awayIt's concrete ... not natural
it's clean, stable and can be walked uponIf there's a need to do something underneath it, good luck
material is readily available and somewhat cheapCan disintegrate in a few years if not done right
any random person can do itIt's a hard surface and rain falling on it will splash hard the foundation wall leading to more erosion


Below are some proposed solutions as found on the web.
Waterproofing using plastic membraneWaterproofing using compacted clay layer


I am curious as what other solutions exist worldwide, especially for old / vernacular buildings.
I need solutions that work, preferably using more natural materials (if available and at a decent cost), but will accept "conventional stuff" if it makes sense.
 
Brett Hammond
Posts: 76
Location: Maryland, USA
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Hi lonel,

They make very expensive synthetic basement waterproofing systems now. In the old days we used to dig around the foundation to the footer, smear roof cement on the exterior, then fabric, and install French drains inside and out with a sump pump. It always worked, and was fairly cheap if you did all the labor yourself, but took us all summer to do each house. If you dig below 4 feet you need a mechanical device to prevent cave ins so you don't get buried alive. With a good backhoe operator, you could probably do it in a week.

Generally speaking, if you can grade the soil one inch to the foot, away from your house for 6 or 8 feet, and run all your downspouts 6 feet away from the house, that usually solves most problems, but not always.

After going what I went through, I would never own a house with a basement. It is so much easier and cheaper to add another story up. The only thing I would want a basement for would be for a root cellar and would never finish it as a living space.

Best of luck!
 
Travis Johnson
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I echo what Brett states. I would not live in a house with a basement either. Here in Maine it is even more silly with our wet weather, cold climate and frost heaving. A concrete slab on grade eliminates all those problems and allows radiant heat and geothermal heat to be introduced into the house easily.

My parents had a fairly big house with a basement and they had so many water issues that after it burned to the ground, like me, they put up a house on a concrete slab. Its not a small house either, 5200 square feet.
 
Ionel Catanescu
Posts: 174
Location: Timisoara, Romania, 45N, 21E, Z6-7
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Thanks.

I don't have a basement, i was just too lazy to make my own drawings and took some from the internet that happened to show a basement.
My foundations are just some 12" diameter piers going to the frostline, on top of which there's a grade beam.

I need to take care on what's outside the grade beam, shedding rain water away so it does not get underneath and inside.
 
Eugene Howard
Posts: 38
Location: Missouri
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I'd like to offer a different opinion that either Brett or Travis. I lived in a house with a basement (one we built) for 25 years and now live in a house on a slab, and I'd take the basement option 100:0. Done right, a basement has a lot of benefits. Done wrong, I agree, it would be a nightmare on par with the slab home I have now, which if done right, would be better, but this one was done wrong.......really, really wrong.

So what did we do right? Looking at the OP's two sketches, "done right" would be the second sketch, with several improvements to it. In our area, normal rebar schedule would have rebar grids on 2' intervals. We doubled that and also enlarged and doubled the rebar in the footings. That was to prevent any settlement cracks. On the outside, rather than compacted soil, we backfilled with gravel to get enhanced drainage to the footings. We used the same drain tile schedule as shown, plus a third drain tile on top of the footings level with the basement floor. Many, if not most builders only install that one single drain tile at the base, level with the floor. That lets the water table under the floor and around the footings remain high. We got rid of the water the moment it entered. We also built the house slightly elevated, such that the slope around the home resembled a pyramid, so any surface water from rain or gutters drained away from it instantly. Lastly, as backup insurance, when the basement floor was poured, 2x4's were nailed to the foundation wall....narrow side up, but each of them nailed to the wall at a 1% or so slope, with the low side ending in a floor drain. When the floor was poured and 2x4's removed, that left a narrow 1 1/2" gutter around the inside perimeter of the basement, so in the unlikely event the walls ever did crack and leak, any water that entered would run down the walls, to the gutters, to the drains and be gone. That never happened once in 25 years, but was there if it had.

To achieve all of that required almost no additional cost over conventional basements and only a small amount of tweaks and effort over and above what is normally used. The difference was night and day. We lived in that house 25 years and never once had a leak or a drop of water enter. We had a dry basement that could be finished or used for storage. Benefits of that are double the floor space for only the additional cost of excavation, basement walls and the floor framing. Same footings, same concrete as would be used for a slab. That also allowed all duct work for HVAC to be run inside the conditioned envelope of the house, as well as all plumbing, with gave a person access to the floors to make changes or repairs as needed.

By comparison, my daughter's home also has a basement. It was built poorly, has cracked and leaked multiple times and is a nightmare for them. They used a foundation repair company and their solution was a total joke. The house next door to them was built the same way and suffers even worse. They also spent a wad on foundation repair and in my opinion, the place should be torn down, as it is that bad.

So you can have a dry basement that will last, but you need to do it right when you build it.



 
Ionel Catanescu
Posts: 174
Location: Timisoara, Romania, 45N, 21E, Z6-7
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Thanks Eugene.

Basements can work but only if done right, as you showed.
My area is a former swamp, very clayey-silty soils with shallow groundwater present in many locations.
Some sites have water at 2ft depth but at my house location, water level is way lower, about 13ft down.

I don't have a basement as i don't need it.
The floor is elevated atop the ground beam by almost 2ft.
Even so, i prefer to let / help water get away from the foundation / ground beam.
Less water, less movement in the clay and less thaw / freeze issues.

Around the house perimeter i intend to build a sidewalk sloped such as to let water flow away.
This sidewalk will end in a gravel ditch, with or without drain tile, i haven't decided yet.
This ditch will then slope to a dry well far away from the house, most probably a mulch basin of sorts.

My only remaining issue is how to do this sidewalk.
I'm pondering laying flagstone in a gravel bed since it's cheap, weather resistant and good looking.
Some water will flow over the flagstones but some will inevitably pass thru the joints.
Therefore a water barrier under the gravel is necessary, so that all water ends in the drainage ditch.

This barrier could be plastic sheet, bitumen membrane, a layer of heavily tamped clay, or something i haven't thought about.
I am biased towards natural solutions but in the end, the solution that works will be chosen.
It is this part i need advice for.
 
Travis Johnson
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Personally, I would want a sidewalk around the perimeter of my house as much as I would want astro-turf for a lawn.

I would think a better alternative would simply be to add a covered porch all the way around, letting you get more usable living space and yet redirecting the water from around the basement to much further out. I don't mind investing money to solve a problem, but it seems like if I was to invest money, I would want something more than just concrete or flagstone to stomp on. A few posts, a bit of framing, some flooring and a roof; and for not a whole lot of money, you would get a lot more usable space.
 
Ionel Catanescu
Posts: 174
Location: Timisoara, Romania, 45N, 21E, Z6-7
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Travis, makes sense as that's something i wanted to do.
But intersecting local regulations (fence clearances and other aesthetic junk) with the usual sizes of postage stamp properties sold today - you have almost zero crossing.
It was hard enough to design the house to be livable, according to my wife's and my own standards, considering the current limitations.

Just for an example, if you have a post (wooden or otherwise), then that's considered house perimeter (limits) and obeys all the nasty stuff mentioned above.
Does not matter if it's a porch or a wall.
We've done a porch this way on one side of the house, 10ft deep so i'm well covered.
It took a lot of space as we had to move the whole house to the back by this same distance (front fence to first post / house wall distance has to be an exact number), and will cost a lot in taxes (it's considered inside the house) but there was no other way.

On the opposite side of the house there will be a lean-to greenhouse so that's covered also.
The other 2 sides don't have any posts or anything attached.

Without posts or heavier supporting structure, eaves overhang is 3ft.
It protects pretty good the side / foundation from usual, slow rain.
But we get also heavy, windy, diagonal rain and there's a lot of water in these.
3ft overhangs are not enough protection.
Only thing i can do is to do this 3ft wide "sidewalk" thing that on at least one side of the house might widen to double that turning into an open-ish "porch".
If a cover is needed, it will most likely be some vines, like grapevines and that's only good for summer shade.
It won't stop rains from getting thru.

 
Eugene Howard
Posts: 38
Location: Missouri
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If I lived in an area with a high water table, I would not have a basement either. That is simply asking for trouble. I would also not want one if having one required a mechanical means of lifting water (such as reliance on a sump pump to keep my basement dry). In areas I've lived, there is generally enough slope and elevation relief that water can drain naturally.

We don't seem to be offering many solutions, but we are not in your area. So a good solution for you might be to look at what others in your area have done. What have your neighbors done to solve this problem?
 
Ionel Catanescu
Posts: 174
Location: Timisoara, Romania, 45N, 21E, Z6-7
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Eugene.

Welcome to my concrete swamp (pun intended).

As i said in my first message, the solution to ANYTHING is CONCRETE.
And if that does not work (and it happens), the solution is MOAR CONCRETE.

Basically a 10cm / 4" thick concrete sidewalk slab (all aaround the building) with bitumen caulk to the foundation wall.
No other drainage present unless there's an esoteric client or architect.

I'm having some issues with this solution, mainly the CONCRETE part.
It seems i'm pretty lonely in my feeling chamber 
 
Casie Becker
gardener
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Location: Just northwest of Austin, TX
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I feel like this is an obvious question, but are you factoring gutters into you plans? They catch runoff from the roof and redirects it away from the walls of the house. We just finished getting a quote for replacing ours (long story) but even not working perfectly we usually have a dry section of earth against our house walls in all but the most torrential rain events. Even in those it still directs the majority of the water away from our foundation. We direct some of it into rain barrels and a cistern, but even on heavy rain produces enough to fill all of our catchment. I can't speak to it's application for basements, but I can't see controlling that much of the water being anything but a help.
 
Ionel Catanescu
Posts: 174
Location: Timisoara, Romania, 45N, 21E, Z6-7
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Hi Casey.

Gutters are present.
But they can only divert water that lands on the roof.

Imagine rain falls straight from the sky, 90 degree to the soil surface.
Some falls on the roof and is diverted by the gutters towards your discharge of choice.
The perimeter of the house is protected by wide (3ft) overhangs.

Now imagine there's wind blowing the rain at 45 degrees to the soil surface.
What falls on the roof is diverted by the gutters, just as before.
But now, some considerable amount of rain will splash on the house walls and perimeter foundation (grade beam / elevation).
You'd need 10ft overhangs for this not to happen.
It is this water that i'm trying to shed away from my walls and foundation.
 
Casie Becker
gardener
Posts: 1474
Location: Just northwest of Austin, TX
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Okay, I thought it was worth checking. Sometimes people get so focused on one aspect of a problem that they miss low hanging fruit. I've seen it happen enough times that I feel like it's always worth double checking the obvious.
 
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