Your thoughts on my basement plans

[tbrooks26]

I agree with you there, depending on soil conditions of course. It will probably work perfectly fine. Although, if you could get some type of drainage system around the bottom/under your slab, without disturbing/backfilling the sides, it would be a little extra security for down the road. And as you said as long as your not distubing anything else, any water that gets there will be minimal, and doing so should not invite water from anywhere else. Either way you go, at least your putting alot of thought into it, and not just doing something totally wrong, as I've seen many contractors do.

 

[BitChin1]

Eddie I think you logic makes sense and is part of a "best practices" approach for basement - that is prevent water from getting there in the first place. The drain tile (form-a-drain, pipe etc) primarily serve the function for removing water that gets to the foundation if your approach of stopping it fails.

I have heavy clay in my area and for the most part water drains away and does not soak into the clay - but there are times when we have extended periods of drought where the clay dries out so much that cracks, crevices and canyons develop - if this occurs near the basement then your first line of defense may fail.

Other times with extended slow rain the entire area of clay seems to become saturated (even on top of berms/hills) and at this point it seems to be a muddy mess for a long time as the water does not drain - your edpm if installed and sealed perfectly probably will stop this water if it does not get too deep around the foundation (need to do some math to determine what "too deep" is such that the house will float) - on the other hand the edpm along with a foundation drain/gravel system to daylight will allow the water to drain away.

Most wet/damp basements are ones where the contractor did code min or "what ever the inspector allows them to get away with" - house being built near me this week used the clay that was excavated as back-fill - no compaction beyond what the high loader could do with the bucket - this house will have 6"- 12" of settling by next spring and the clay cap will work more like a catch basin funneling water toward the foundation - should have used crushed stone compacted in < 12" lifts to grade level then some sort of "cap" (clay would be minimum with 4"/8' slope), but that is not required by code and would cost more :-(

Net is I think you need to determine or convince yourself if you can truely prevent water from accumulating at the foundation for the life of the building - if so then your plan works (probably is an expensive over-kill actually) - if you can not guarantee this then your edpm approach is better than no damp/water proofing but without the ability to drain accumulated water it will not protect against large volume events (and by large volume you may only be talking a few inches).

Fun thread this has become

 

[buickanddeere]

Lots of drainage on the outside of the exterior walls . Down below the footing level. Insulate the wall well on the outside and underneath the floor. Backfill will drainage stone . Water won't get to the wall. The wall and floor won't be cold and wet on the inside .

 

[Streetcar]

When you excavate for the basement, you disturb the surrounding soil. The adjacent basement will lead to the surrounding soil drying out quicker.
Both situations can lead to soil cracks which can direct the water on the foundation.
Eddie
your method is a thicker than normal waterproof membrane. You are eliminating any method to get rid of water that does reach the foundation.

 

[dstig1]

Eddie, One thing that you may be missing is the purpose of the backfill. Free draining backfill (3/4" washed, for example) serves 2 purposes - for one, any water that gets near the wall will freely drain to the footing drains where it can be removed, but the second point is often missed - it breaks up hydrostatic pressure. Because it is so open, any water that gets in has room to expand, and that kills the pressure that wants to force it through your basement wall. Clay is the #1 enemy of this as it creates MASSIVE hydrostatic pressure when saturated. If all stays as you know it now, maybe you will be fine. if anything changes, then you may be hosed. Risk vs cost. Cost minimal to mitigate risk, so why not do it?

You also said "If I keep the water form ever getting there, why would I need to drain it?" Being experienced in the field, you know the first rule of water: It wins. Always. You cannot "keep it out". Something will happen to cause a leak, and then you either have systems to deal with it, or you are hosed (again).

BTW you mentioned always trying new stuff in bathrooms and such. All those new things you are trying have been tested and evaluated by engineers, building professionals, code officials, etc. They may not have a lot of history behind them, but they have science and extensive testing. You are going out into the unknown here on your own.

Still your call, but I don't get the resistance...

 

[MossRoad]

...What I'm trying to figure out is why my idea of not creating a path for water to get under the basement with gravel would lead to water getting into a basement? ...

I see your point. You're thinking, "If I put gravel next to the foundation, and we DO have a 100 year rain, that will put water right next to the basement wall, and if the sump pump can't handle it, the basement will get wet. If I'd just have left the undisturbed clay there, no water would have gotten down there in the first place." I tend to agree with you. However, currently, nobody does that. Why? Heck, I don't know! :laughing: But my guess is "been there, done that, didn't work out well" will be the reason. Or you could be on the cutting edge of economical basements in clay soils.

I admire your experimental nature. My father often experimented with construction techniques, building materials, etc... on his own home. Most things worked out really well. One thing I remember most, though, is he was big on drainage. He always spoke of planning for 100 year rains. We had swales in our ivy beds that were integrated into the landscaping. No one knew they were there but us. A few times in our time there, we'd have extreme rains and all the water just went around the house and down drains in the yard that exited to the lake behind the house. There was also a 4' band of crushed limestone around the entire house. He had drain tiles buried in that crushed stone that exited to a lake. Any roof runoff and rain hitting the side of the house would simply vanish into the limestone.

Does anyone do basements in that part of the country?

 

[EddieWalker]

Here's what I'm thinking happens. A contractor is hired to dig a basement. He goes in to the sight and digs it regardless of soil type or building location. He doesn't really care, he does this every day, year after year. You tell him how deep and how big you want it and he makes it happen. He digs it bigger then he needs it to be because they need to get to both sides of the wall when building the walls. They build the forms, dig out the footings and pour the floor. Then they work their way up with bock, or they build forms to go on both sides of the wall. They need enough room to work on both sides of the wall, so there has to be enough dirt dug out for this to happen. I've sen pics where there is as much as 4 feet of space outside the basement wall that is dug out, but most seem to do as little as possible with less then 3 feet.

Once the block wall is built, it needs to be sealed. Block is the worse thing in the world for being water tight, but even a solid concrete wall can have a crack in it that will allow water through, so either way, you need to water proof the exterior wall. They wrap it with epdm rubber. From what I've read, it's not very thick, which leads me to believe they use the minimal thickness that they think they can get away with. Since it seems to work most of the time, I'm lead to believe you really don't need that tick of a barrier to keep water out.

Then they backfill with whatever material is specified. I think this varies around the country. Dirt is going to be the cheapest, but rock will be easier since you don't have to compact it and it doesn't settle. Either way, both materials are porous and allow water to get all the way down to the bottom of the basement quickly and easily.

Now the question is what to do with the water that accumulates under the floor? You can either pump it out of there, or drain it to daylight if you have a grade that allows you to do that and remain on your property.

I'm not saying this is bad, what I am saying is that by it's very nature, it is designed to fail and then designed to deal with that failure. Creating a path for water to get under the basement is a design flaw that I think is inherent in every basement.

While I can't speak for any other soil type then what I have here, my red clay does not crack or expand very much when it is dry or wet. It is a very good building clay that is highly sought after in my part of East Texas. There is some very bad stuff around here, and just about all of it is horrible to build on the closer you get towards Dallas, but here, it's as good as you could hope for. Even after an extreme rain event, the top couple of inches are nasty where it puddles, but you can still drive through it with the tractor because the tires will sink through the soft layer to the hard base that will support the tractor. Trucks and other vehicles have more problems because of how sticky it is and how it builds up on the tires. Same with walking on it. But the base is still solid and holding water, it's just that couple of inches of surface muck that causes problems. All my roads are crowned, and I can drive on them the day after it rains with just about anything I have.

There are a few basements in this area. I know of a few with sump pumps in older turn of the century farm houses, but they are just concrete walls and floors long before rubber was even invented. There are no liners on the outside of any of the basements that I'm aware of. Every one that I know of was built in the 70's or earlier.

And to address a comment about cutting corners that bothers me. I feel that by spending the money on a very high quality, heavy duty EPDM liner and the best glue/solvent that I can find, that in my design, I will be building superior basement to the traditional methods used around the country. I am not trying to cut corners, I am trying to make something better that will last longer and remain dry forever.

I think the biggest difference in my thinking to those of you who suggest I do not do this is in our faith in the rubber liner and my ability to get a perfect seal with it. Failure will only happen if the liner fails. If it remains intact, there is no way water will ever get into the basement.

As for the concern about hydraulic pressure lifting it out of the ground, I don't believe this is possible. The amount of weight and surface area that I will have in 16x16 room with concrete floor, footings and walls just isn't possible where it's located. In fact, I believe that if I was able to put this room in the middle of the pond, it would sink like a rock from it's weight and size.

 

[BitChin1]

Eddie I agree with your logic (except for the concrete boat sinking - it will float ).

The big concern I have and I think your need to answer for yourself is the design relies on no/minimal water getting to the foundation - you are providing no means to relieve hydrostatic pressure and no means to drain it other than through the clay.

You are providing a a primary plan - attempt to avoid water getting to the foundation by draining surface water away and you are providing a backup plan - edpm liner to resist the hydrostatic pressure.

In most cases a third layer is applied as a backup to the backup and this is the drainage system.

No one here can assess your particular soil from a far so you (or maybe in consultation with local soil engineer) need to determine if you can rely highly on your soils ability to shed water in all circumstances
You are correct that in building your home home you can pay great attention to key details and likely be able to provide good surface drainage and well sealed liner.

One other reason the basement excavation is a bit wider is to allow for "some" cave-in that will not get into the basement footprint - some soils this is a big deal others it is not necessary.

The two areas I still have concern with your proposal is that it does rely on the surface drainage and lack of ground water along with perfect sealing of the edpm (the latter not being necessary if the former is perfect) - in my experience the activities I performed myself I could get to a high degree of perfection (not always on initial attempt) but the efforts of hired help/contractors was never in the same league of perfection (I have only built 4 homes), but I will say the excavators I have hired were the best at getting to what was requested.
I have used epdm for koi pond liners on several ponds - they all have leaked - not sure why and possibly due to access to UV but they have all leaked (small leaks, but still they leaked)

As for the homes in the area that are dry - this points to the area soil being "good" for your proposal at limiting the surface and ground water from accessing the foundation because "concrete leaks" (it is NOT waterproof and does not need cracks to leak) - if water was getting to these foundations/basements they would be damp, so given this you do have some support that your proposal will work in local conditions and is not just wishful thinking. Many of the folks on here are from areas where this example does not exist

Probably a good time to think about actual construction sequence and assess is this possible to pull off successfully

 

[jk96]

Eddie,

if my math is correct and you dropped your basement in the middle of the pond. The volume of air would lift almost twice what the basement would weigh. I think it will float. Reminds me of the "will it fly" thread that went on forever.

Jeremy

 

[tbrooks26]

I maybe wrong, but if the basement is lighter than the volume of water it (could) displace, it will float. 16x16x8(?)=2048cubic feet. Water weighs about 60lbs per cuft so your basement would need to weigh more than 120,000lbs to sink in a pond.

Edit: with 12" thick walls and a 4"slab, you would be approx. 90,000lbs