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-   -   Comparison of subfloor waterproofing systems (http://www.diychatroom.com/f19/comparison-subfloor-waterproofing-systems-421/)

formarley 03-16-2005 08:07 AM

Comparison of subfloor waterproofing systems
 
My wife and I have a 1930s home with an unfinished basement that gets wet with rainstorms, we think mainly when the water table rises.



We have made sure our leaky gutters are fixed; we've re-contoured the parts of our lawn that channel water towards the foundation. We just have a high clay content in our soil (which holds water), plus the water table in our area is very high, so whenever we have larger rain events (which seems to be most of them) we get wet. The ground water from above, and the water table from below create pressure on our basement floor and walls and cause it to seep water through cracks.



We have gone to the trouble of having two "sub-floor waterproofing" contractors come into the house and provide estimates. This is where they come in and excavate around the inside walls of your basement down to the footings and install gutter-like channels that move leaking water to a sump pump to be removed from the house. Though the science behind what they offer is the same, there are differences that make me wonder (cost differences aside). B-Dry and Basement Systems (JES Construction) are the two contractors we've looked at, though there are a ton of them out there that offer a similar product.



Is anyone aware of any information where sub-floor systems are compared; or does anyone out there have experience with multiple systems so we can get a better idea of the better/best system to use?

pipeguy 03-16-2005 05:49 PM

Please tell me a couple of things:
1. What town and state are you in?
2. Is your basement a 'walk-out' or is it entirely below grade?
3. Are you near the water or a wetland?
4. Do you see dirt stains coming in through the cracks?
5. Do you currently have a sump pump?
6. Do you have neighbors with the same problem?

I think systems that serve to manage water once it has entered your basement are of questionable value. If your problem is actually a water table issue I believe you'd be better off using a system that lowers it to the point that it either doesn't enter your basement, or otherwise relieves the hydro-static pressure on the outside of the wall - like a drain tile sysytem.
Generally, it's going to take more than a single large rain event to substantially impact the height of a water table; particularly in soils with high clay contents. It sounds to me like your problem is still water being conveyed from the surface down along your basement walls. Can you install a water barrier either at the surface or just below (such as a waterproof membrane) in connection with a shallow drain tile? Just a thought.

formarley 03-17-2005 04:18 PM

Thanks!

1) We are in the central Virginia area -- several miles west of the fall line of the James River where there are large granite deposits and clay-type soil (we are also in a high radon area). The water table is just real high in our area.
2) Basement is not a walkout (though there are some small windows, but they are several inches above groundlevel, water doesn't come in through or around them...), an eight foot basement, about five feet of it is underground.
3) We are about 1/2 mile from a major river, about 75-100 feet above the flood plain.
4) There are some dirt stains on the walls. There are also areas of the basement where there are no stains, but there is plenty of water seeping in through the floor cracks adjacent. The recountouring has probably reduced the stains a little (obviously it worked it a little...)
5) No sump pump. Just a drain that feeds to the storm sewer (normal water in the basement is not from backup from the drain -- though we had a major problem with that last year)
6) Finally, I haven't spoken with anyone in our neighborhood that doesn't have this problem.


Yeah, when droughts break it takes awhile for the basement to start to seep. However, after several rains it will catch up. We've been above average for about two years now, plus we had a freak 15 inches from a tropical storm that blew through last September -- we've pretty much been wet ever since, though the winter has been fairly dry.

Previous owners tried patching some of the floor cracks, but they opened back up over time (plus water just started coming in at more difficult places to cover like where the floor meets the foundation wall...)

We've talked about putting down a membrane. However, we figured this would just help keep the pressure up on our foundation walls. I don't exactly know what a shallow drain-tile is; I assume this would be something higher than the foundation footings (where B-Dry and folks like that put in a drain-tile system that is at or below the level of the footings)?

pipeguy 03-17-2005 05:30 PM

Quote:

Originally Posted by formarley
1) We are in the central Virginia area -- several miles west of the fall line of the James River where there are large granite deposits and clay-type soil (we are also in a high radon area). The water table is just real high in our area.
3) We are about 1/2 mile from a major river, about 75-100 feet above the flood plain.
We've talked about putting down a membrane. However, we figured this would just help keep the pressure up on our foundation walls. I don't exactly know what a shallow drain-tile is; I assume this would be something higher than the foundation footings

Back in '79 I worked building some sewers in the Mechanicsville area of Hanover County - not far from the Chickahominy River (or swamp, as it were) and very near a contributing creek. Until you got up more than 40 or 50 feet above the creek level the the soil was red clayey sand with fine sand and running water at about 8 feet down. After you got up above 50 feet or so it turned to stiff, sandy clay with no water.

If it were me, before I spent any real money on a fix I'd be inclined to install a monitoring well, either outside the foundation wall or through the basement slab, maybe 6" diameter and to a point 2' deeper than the basement floor, so I could SEE and record over time just what the 'watertable' is doing. I'd really want to KNOW that it was a watertable issue, and not just a run-off problem, before I decided on a solution.

The membrane idea was geared to solving a run-off problem. What I meant was install a horizontal membrane around the house, maybe 12" below the surface (or deeper if landscaping is an issue) and 5 feet wide and lapping up against the foundation wall. Then put in a gravel and perforated pipe system over the membrane and against the foundation with the pipe extended to 'daylight'. Cover all that back to grade. The membrane would act as a waterstop as rain drained down through the soil and the drain tile would carry accumulated water away. This is not a solution if the water table is actually the issue.

formarley 03-18-2005 07:58 AM

O.K., I understand what you're saying; we, in fact, did put sheeting from the foundation maybe 10 inches down and the length of the bed out from the house (4-5 feet) about a year and a half ago . However, given we are at the bottom of a small rise, it wouldn't surprise me if water still worked it's way around the cover.

So as far as the test well, I reckon we could tell pretty quickly if it is water table issue, maybe as soon as we dig it? It would probably makes sense (and in some ways easier) to dig the test in the basement since that is where the water is coming in?

echen1 10-22-2009 10:03 AM

So what happened? I have a finished basement very similar to yours
 
Hello,
I saw your postings from a few years ago about your basement water seepage, water table, clay soil and being near a river. My house and basement have exactly those conditions too. Did you ever fix it? Did you do the guy's suggestion and dig a well?

Thanks!


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