waterproof outside or sump pump/french drain inside?

[Anonymous]

I'm confused on what the best strategy is here. We have a 1940s brick home with a concrete cinder block foundation (and a concrete filled footer). We have some water in our walls that has been building over time, as told by moisture meters and air tests showing mold.

We are hearing two different stories from the water/drainage companies. Some suggest that we dig around the house and re-seal the foundation which will prevent surface water from coming through the foundation cracks. These people say that treating the outside is treating the source of the problem and that we would still be allowing water inside our home with a french drain system (which is true). Then others tell us it would be smarter to treat from the inside, by doing a combination french drain + sump pump. They say that the inside treatment will work forever, whereas the outside waterproofing can still fail since they cannot truly seal beneath our footer. Plus when the water table rises and drains potentially back up, the sitting water might come up in ways that waterproofing the outdoor foundation can't handle.

We are in the process of getting quotes so I don't have a price estimate just yet to compare, but since this is our family home and we do want to hang out in the basement, I'm interested in doing this right (without doing both inside and outside). Any advice?

[Anonymous]

We have a leaky basement (ie water sometimes trickles through the foundation but we never get true flooding/standing water). As a non-professional, I recommend the outdoor fix. My understanding is that for a sump pump to work it needs a certain amount of water, meaning that it will kick in when there's a big heavy rain but it's not going to do much for small amounts of water.

I would also suggest a good dehumidifier. We bought a large one at Costco and we run it a lot, to minimize the moisture in the basement

[Anonymous]

Depends on what you ultimately want.

On the outside, you need to both seal and install a drain system that leads to a sump pump that discharges the water at least 10 feet away from the foundation (run a drainpipe away from the sump pump discharge). That will keep your walls and basement dry. It can also be expensive to do with all the labor involved.

On the interior French drain, the basement will have humidity (and potentially mold) as the water will still be penetrating inside. It only helps keep the basement floor from having standing water.

[Anonymous]

Alright, seems like inside sump pump is going to be a cheaper option, but if the potential for mold is still high then I would want to focus on outdoor solutions. The inside contractors have said they will put antimicrobial cleaners inside the cinder blocks to clean and then the standing water will no longer be standing inside the walls, so mold will not build. Any other thoughts on potential for mold growth with internal drains? I feel like a lot of the homes we saw in DC had them.

[Anonymous]

Anonymous wrote:Alright, seems like inside sump pump is going to be a cheaper option, but if the potential for mold is still high then I would want to focus on outdoor solutions. The inside contractors have said they will put antimicrobial cleaners inside the cinder blocks to clean and then the standing water will no longer be standing inside the walls, so mold will not build. Any other thoughts on potential for mold growth with internal drains? I feel like a lot of the homes we saw in DC had them.

As long as you have moisture inside a space, you have the potential for mold/mildew to build up, no matter what is done with anti-microbial, etc.

[Anonymous]

OP here... Only have 2 quotes so far. Just under 4k for the sump pump inside. Just over 16k for the outside waterproofing on 1/2 the house because I can't afford to do the whole thing. One area is a concrete patio that will be a huge pain to deal with on the outside and they didnt even give a price on it bc it would require redoing the patio. I'll wait for more contractors to weigh in in person, but I'm obviously tempted to go the 4k route even though I previously stated I wanted it done "right"

Any others have mold concerns and sump pumps? Did it help at all?

[Anonymous]

Don't do a French drain.

Op, look at rainscape websites (like the master gardeners, nps) for the actual effective ways to deal with storm water run off.

[Anonymous]

Both. Sorry to break it to you. Add to that regrading as a possibility.

We are also a 1940s Colonial and have the misfortune to set sideways on something of a hill. You wouldn't really think it was a hill until you saw the rain pouring down. We discovered the hard way that you need to address the outside options to keep water from coming in from above ground, but you also need a sump pump to take care of water that comes below ground. We spent about $10k on regrading, French drains, running pipes underground from the back yard to the front (land slopes that way), and repaving the sidewalk after tearing it out to do all this. We already had the sump pump but it wasn't enough. Since we did this 4 years ago, we have not had a water issue (knock on wood!) except that when it rains really heavily, water still comes under the basement door where the regular drain outside the door can't keep up. This is a very common story around these parts with these old houses. Unfortunately we seem to be getting more and more heavy rains where this is an issue -- probably 3-4 times a year these days.

Before we did the regrading and drainage, at various points in the years prior we spent $$ redoing the gutters, digging around the house and resealing the walls, resealing from the inside, etc. All were necessary but the regrading, French drain, and pipes were what really made a difference.

Oh yes, and with the sump pump, you have to check it periodically. The battery on ours died one time and we got a massive flood. Thankfully insurance covered it but the basement redo was a humongous pain.

[Anonymous]

Anonymous wrote:OP here... Only have 2 quotes so far. Just under 4k for the sump pump inside. Just over 16k for the outside waterproofing on 1/2 the house because I can't afford to do the whole thing. One area is a concrete patio that will be a huge pain to deal with on the outside and they didnt even give a price on it bc it would require redoing the patio. I'll wait for more contractors to weigh in in person, but I'm obviously tempted to go the 4k route even though I previously stated I wanted it done "right"

Any others have mold concerns and sump pumps? Did it help at all?

I can understand your desire to do it "right," but you can't really waterproof a concrete block foundation on a 40s house after the fact. And, as you've found, it's insanely expensive. Save some money—address your exterior grading and downspouts first, then do the interior drain and sump, and get a good dehumidifier, and drain it into the sump pit. Make sure you get a sump with a battery backup, and maintain it.

[Anonymous]

+1 try regrading your yard first. It is the most simple and transparent way to solve the root of the issue.

[Anonymous]

Thanks everyone! I'm going to start with the sump pump and regrading. We have a dehumidifier running down there but we could put our second down there too. They fill after 10 hours so I'm constantly dumping them, having a hose to the sump pump would be nice.

[Anonymous]

We have a sump pump and a french drain outside. The french drain routes most of the surface water around and past the house and the sump pump takes care of what's left underneath and what comes in the basement stairs area drain (it's not covered, it's like a little below grade stoop/patio thing and that drain goes to the sump pump to be pumped back up and out).

I say this is a "do it right" situation and you should not hesitate to spend time talking to different folks - builders, landscapers, drainage/basement specialists. They all have different approaches. It's like seeing an ortho and a neuro about your back problems.

[Anonymous]

You need both. No new home is allowed to be built without both