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Finishing 100 yr old basement with minor hydrostatic water issues

This is my first post here- My husband and I own a 100-year-old home in St. Paul,MN (lived here 5 years). Our basement was cosmetically finished around 1970 (walls, ceiling, but NOT the floor). We'd like to make it an even better living space and update it, and finish the floor, but we are concerned about how to properly deal with potential water issues.
We have witnessed some minor, seasonal water seepage from the floor and we think the problem is mainly hydrostatic pressure. Some years there hasn't been any water at all.

The foundation walls are 19-inch thick limestone, which is in really good shape. The floor is about 2 inches of 70-year old concrete. We do have adequate headspace and an egress window already.

Here is what we have considered:
1) Installing drain tile
2) Sealing the floor and/or walls with a product like Sanitread (though we're worried that sealing a limestone foundation won't be good in the long run).
3) Repouring the floor, reinforcing it and making it thicker, and with modern cement additives that will help make it resist water and give it resistance to hydrostatic pressure
4) Not finishing the floor, so water can seep , and dry out if needed (the least interesting option to us)
5) A mongo dehumidifier (*we already use a small one*)

We have already landscaped properly around the house, and we have long gutters, etc

We would like to solve this problem from the inside- Digging on the exterior is out of the question cost-wise.

Can any of you recommend what options (or combinations of options) might be best- and things we haven't thought of?

Also- if you have any suggestions on how to heat the space efficiently (it's currently got 1970's era electric baseboard heat)....

We're pretty handy and have done a lot of work on the house so far- we're not scared of work (like taking out the floor and re-pouring it). We just want to make the right choices and only have to do this once. We know mold is a terrible problem to have, and that's the last thing we want.


Re: Finishing 100 yr old basement with minor hydrostatic water issues

Water is always best stopped before it touches the structure- meaning from the outside. Since that is not on your list of options I would suggest beginning with the floor. 2" of concrete is not adequate for a floor (or anything more than a easily replaced step-stone). I'd go for 4". I would also either slope the floor toward a opening that drained outside or to a sump to handle larger water ingression should you find yourself in a bad situation where it is needed- better safe than sorry. If the entire basement is underground I'd slope toward the perimeter and cast in a gutter drainimg to a sump and build walls inside of that to enclose the space. You'll need to ventilate the space behind the walls and insulate them too, but it will leave you with a much more comfortable living space this way. This may also allow you to tap into your existing HVAC system for climate control if it has enough capacity. Dehumidification inside the space will likely be needed. With the enclosed space away from the exterior walls you may have enough capacity in the unit you now use, as most of the humidity will be outside of this space.

Since most homes have ducts and piping under the floors in a basement I like to use acoustic tile ceilings so that you can access anything for service- removing a sheetrock ceiling to fix a leak is a mess and you're likely to have to get in there sooner or later. It isn't the most stylish but with today's selection of tiles you'll find something you can live with. Get an extra bundle of these and store them inside the area well off the floor so you'll have a match if you need a replacement tile later on.

I'm sure others will chime in with suggestions which may vary from mine. You must remember there are many ways to go at a project like this and each will have it's pros and cons. In the end you will have to decide what you think best and go that way; all we can do is let you know the options and methods we are aware of ourselves.


Re: Finishing 100 yr old basement with minor hydrostatic water issues

You can try to use a moisture barrier that rolls onto the concrete. Arizona Polymer Flooring makes a product that reduces the amount of moisture vapor coming threw the concrete.

MVL Concrete

Re: Finishing 100 yr old basement with minor hydrostatic water issues

You should try for limestone tiles because of these tiles are highly moisture resistant and durable.*

Re: Finishing 100 yr old basement with minor hydrostatic water issues

After visiting and reviewing your homepage I have to congratulate you on the hard work and excellent results you have achieved so far!

I didn't notice any mention of a low-cost sump pump---to be installed where the water is coming into the basement----if you don't have one, this should be the first consideration to protect the hard work and expense you have gone through that will be lost----even a moderate rainstorm can cause considerable damage if a flood occurs.

There was an excellent article in Popular Mechanics in 2005 by Merle Henkenius entitled "Basement Blues" about the pesky problem of keeping water out; his theory is that any hydrostatic water pressure has to be dealt with from the outside of the foundation---the plan of attack is to eliminate as much as possible any rainwater accumulation around the exterior foundation.

Your homepage indicates that you have installed "long downspouts" ---I assume this refers to installing horizontal extensions to your house gutter downspouts in order to get the roof runoff as far away from the house as possible---this is a good move; I would hope that you have stood out there in a rainstorm and noticed how much runoff water is coming out of the horizontal sections, and hopefully it is far enough away from the building foundation to make a difference, and that it is not making its way back toward the foundation.

I see no photos of the house gutter drainage system, and assume you have vinyl or aluminum gutters ON ALL EAVES and any dormer sections that are conducting the runoff to downspouts that are directing the water away from the foundation; it should be noted that the roof drainage system, as well as any near-foundation catch basins and drywells are relatively inexpensive items to install as they are classified as (usually) 4" diameter drain pipe that is only 1/8" thick (SDR-38: some have perforation holes to act as drain tiles)---as opposed to much thicker and much more expensive Schedule 25 drain pipes used in interior plumbing applications.

Thus, following Henkenius, it is an excellent DIY job to install buried perimeter drainage around the exerior of the house foundation and route it all to a drywell some 15' away from the foundation----this is all gravity-fed using a pipe pitch of 1/8" to 1/4" per foot-----digging down to the base of the exterior of the foundation is no picnic, but going all the way down to the base of the foundation is often unnecessary when going down a foot or two may be enough to relieve the hydrostatic pressure causing the leak; often, the roof drainage system can be pitched to direct all water away from the foundation to, say, the back of the house, where it can be routed to buried drain pipes, then directed to a drywell; drain tile (the 4" pipe with little holes in it) is installed in the exterior problem area of the foundation where the water is coming in & then everything is routed to a nearby drywell located as a slightly lower level----the whole system works on gravity (water always flows downhill) at a slight pitch of 1/8" to 1/4" per foot of drain pipe---caution, always call the natural gas co. and local water dept. to determine the buried location of gas, water and electrical lines before you dig.

It's a beautiful sight to have everything buried out of sight, out of mind underground---it really dresses up the appearance of the house exterior, and the plastic drain pipe lasts practically forever, quietly doing its job day in and day out.

This has the added advantage of improving the appearance of the house exterior, where there are no horizontal drain pipes extending from the house to expel water away from the foundation.

Reggie D
Re: Finishing 100 yr old basement with minor hydrostatic water issues

In older homes like you described, stopping the water flow can be extremely difficult due to the path the water takes to get into the home. Most homeowners think the water is coming up from under the floor while it is the exact opposite, the water starts at grade level, flows down and through the wall. Older limestone walls are usually held together with deteriorating mortar that becomes dry and crumbles at the touch. Water easily flows through the blocks and finds a pathway in.

While an underfloor drain tile type system might help with some water that does make it under the floor, most of the water will exit the wall higher off the floor making it impossible to get captured by the drain tile pipe. Since newer poured concrete and older solid rock walls do not have the benefit that hollow CMU (cinderblocks) have, a drain tile system will only help minimally. Products that coat the interior wall have their own limitations, first the wall needs to be extremely dry (for most consumer products) and very clean. Over time the water that pushes through will also push the product off the wall, usually in a very messy manner.

Gutters and grading all help with moving the water away from the foundation but in most situations the damage has been done below grade. With the right kind of soil conditions voids develop in the area around the foundation, water finds it's way into these voids and when there's enough pressure it flows through the wall. I've seen voids several cubic feet when this area has been excavated, even running the length of the footings.

Sealing the foundation from the exterior is the only way to insure long term waterproofing. Allowing the moisture through the walls and floor and then pumping it out is not water proofing but water management. Continual long term damage to the mortar happens even with a sump system.

The only material I've seen that's effective is Bentonite Clay from Wyoming. If the area has been excavated, a membrane is pinned to the wall and a sausage is layed on the footing. If excavation is out of the question, contractors will inject this hydroclay with a pumping and pipe system that does little damage to the exterior landscaping. The idea is to fill the voids and flow the hydroclay (waterproofing version of bentonite) around the foundation. Bentonite is a green natural material that self-heals if the foundation is moving. Asphalt, concrete, epoxy, etc are all brittle and will move (crack) with the wall while bentonite will be pushed further into the cracks.

Most larger commercial and industrial buildings are waterproofed with hydroclay, if you've ever been in an underground parking garage built in a swamp there's a reason you don't see moisture coming through the walls. You'll also notice that they never use an interior coating to accomplish this.

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