Basement waterproofing methods

[steppinthrax]

Have a 3K square foot house, recently purchase. The basement is partially finished. Anyway, there is always a musty smell. Recently I'm seeing surface mold growth on some leather, paper etc. Anyway I've been reading up on methods for waterproofing.


I was told that the basement would likely need a dehumidifier, sump pump installation, by the inspector. I was doing some research and found that you will need to break a hold in the "lowest point" of the basement and dig a trench on the interior perimeter of the inside of the basement (running to the hole). You would install a sump pump in the hole and that should fix most of the issues.

I have checked my gutters, downspouts and all the simple things to find they are working properly. I found a corner of my basement and broke a 15" hole in the concrete. The dirt is moist, but not very wet. I also haven't dug the entire depth yet. I'm curious do I need to do the french drain as well, or can I get away with just the hole. The basement is partially finished and I don't want to tear up the entire basement.

 

[MagnusTheBrewer]

Yes, you need the the weeping tile as well. The sump pump by itself won't do anything but cover the small area where the hole is. Is there any kind of waterproofing on the outside? Do you have any casement windows in the basement? Is your property lower than the surrounding area?

 

[TwiceOver]

Ouch. Step one, never buy a house with a basement without a sump. For sure start with the dehumidifier. Hopefully you can get it in a good location near a drain and have it run whenever it needs to. Be sure to get the kind that will kick on and off depending on humidity.

 

[purbeast0]

growing up in a house that had constant water problems in the basement, this was one thing i did NOT want when purchasing my first home.

i just bought a house that had a b-dry water proofing system installed so i shoudl never have any issues.

http://www.bdry.com/

the inspector did his little moisture test all around the basement during our home inspection and didn't find one area of moisture, which was good news to me.

since the basement is 100% finished, i am glad that i should hopefully never have to do anything down there and it should stay dry. we have a HUGE storm yesterday that knocked out the power for a bit and I went down in the room to feel around the edges of the room and didn't find any wet spots on the carpet. granted, i didn't expect to, but it's good to know that it is dry.

additionally, grading plays a HHUUGGEE role in whether or not you will get water in your basement. proper grading is essentially all you need and you will never have an issue.

 

[steppinthrax]

Yes, you need the the weeping tile as well. The sump pump by itself won't do anything but cover the small area where the hole is. Is there any kind of waterproofing on the outside? Do you have any casement windows in the basement? Is your property lower than the surrounding area?

When you refer to weeping tile, your indicating the trench that needs to be cut into the inside of the foundation, this will run to the sump pit?

I don't have casement windows. The property is built on a hill.

 

[MagnusTheBrewer]

When you refer to weeping tile, your indicating the trench that needs to be cut into the inside of the foundation, this will run to the sump pit?

I don't have casement windows. The property is built on a hill.

Yes, the French/weeping tile runs around the inside perimeter of the foundation wall and is tied into the sump pit. However, since you mentioned the property is on a hill, that tells me you have a grading problem. The ground around your house should not be closer than 3" from the top of the foundation. In addition, the yard must slope away from the house. Do you have heavy clay or caliche soil? Do you have an outside entrance to the basement?

 

[Squisher]

With nothing more than smell being the issue a fan running 24/7 when you're not down there will do a lot toward getting rid of the smell issues. If that didn't work I'd get a dehumidifier, but find a spot where you can plumb it to a drain. You'll soon hate having to empty it regularly.

Without actual water seeping into the basement I think French drains, sump pumps or any talk of weeping tile would be overkill at this point.

 

[MagnusTheBrewer]

With nothing more than smell being the issue a fan running 24/7 when you're not down there will do a lot toward getting rid of the smell issues. If that didn't work I'd get a dehumidifier, but find a spot where you can plumb it to a drain. You'll soon hate having to empty it regularly.

Without actually water seeping into the basement I think French drains, sump pumps or any talk of weeping tile would be overkill at this point.

The smells and humidity didn't appear by themselves. There is a root cause. Putting a band-aid on the problem might temporarily fix the symptoms but, ignoring the root cause in one of the most expensive home maintenance areas to fix is foolish.

 

[Squisher]

The smells and humidity didn't appear by themselves. There is a root cause. Putting a band-aid on the problem might temporarily fix the symptoms but, ignoring the root cause in one of the most expensive home maintenance areas to fix is foolish.

I'm really not trying to dissuade him from finding a root cause, but all basements without some air movement by their very nature of being built down in the ground are full of moist air.

 

[Raizinman]

Dig about a one foot deep trench around the foundation. Pour in liquid tar. Keep doing this for 2 days. Never had a wet basement afterwards.

 

[MagnusTheBrewer]

Dig about a one foot deep trench around the foundation. Pour in liquid tar. Keep doing this for 2 days. Never had a wet basement afterwards.

That would not help if the grading was wrong or, the soil held water.

 

[edro]

You broke into your concrete floor!?
The next time it rains, check it. It could easily fill with water and possibly overflow into your basement.

At least you have the start of a sump pump hole!

 

[steppinthrax]

Yes, the French/weeping tile runs around the inside perimeter of the foundation wall and is tied into the sump pit. However, since you mentioned the property is on a hill, that tells me you have a grading problem. The ground around your house should not be closer than 3" from the top of the foundation. In addition, the yard must slope away from the house. Do you have heavy clay or caliche soil? Do you have an outside entrance to the basement?

The house sits on a hill. A good 20' or so of ground in front of the house is flat, but i quickly slopes down away from the house. The rear of the house is flat.

The soil is sandy.

 

[steppinthrax]

Just spoke to my neighbors. Apparently every house in our neighborhood was built by the same builder, no one has a sump pump. They all said they have a dehumidifier in the basement and that it's a must, you let it run during the day, you usually get about a bucket of water a day. During the winter you can cut it off....

 

[MagnusTheBrewer]

The house sits on a hill. A good 20' or so of ground in front of the house is flat, but i quickly slopes down away from the house. The rear of the house is flat.

The soil is sandy.

Have you actually measured the gradient or just eyeballed it? Do a walk around the house and look for any sign of water damage ie. water stains, white chalky looking marks, insect activity on side of house near foundation, darker concrete or blocks closest to the ground. Speaking of which, what kind of foundation do you have?

 

[edro]

My house was built in 1880. It has a poured concrete floor and field stone/brick walls.

I have a 70 Pint/Day dehumidifier that keeps the basement at 60% RH. (it shuts off every few minutes)
If I set it to 55%, it runs 24/7 and won't shut off. (700W)
I have it draining into a floor drain that is piped outside of the house via gravity.
The house is on a hill. I need to put a membrane over the drain though.

FYI, hygrometers are notoriously inaccurate and drift over time.
To check yours (so you can calibrate it by adding or subtracting %), put it in a ziplock bag with a little tray of salt and water mix.
Make the mix the consistency of toothpaste.
After a day or so, it should reach equilibrium of 75% RH.

I did that with a cheap electronic hygrometer I had. It was reading -6%.
My dehumidifier has a digital meter on it and it appears to be reading within 1-2% (based on its comparison to the calibrated value on the cheap hygrometer).

Have you measured your humidity? It greatly varies based on location (floor, corner, ceiling, wall, etc.)

If you are getting mold, you are likely over 70% RH.

 

[Red Squirrel]

To do it properly it has to be done from outside. It's not cheap. Basically need to ensure there are no cracks in the foundation, if there are they have to be parged in. Then a rubber substance is added, there are various products for this. Then the weeping tiles are added. Then clear stone and sand.

I recently got mine redone. Some pics here.

If you happen to have access to an excavator and dump truck you can probably do it yourself otherwise there's no point in renting all that, it will cost you almost as much as getting a pro, and with a pro at least the work is guaranteed and they have insurance if something goes wrong (ex: accidentally smash excavator into house).

 

[steppinthrax]

To do it properly it has to be done from outside. It's not cheap. Basically need to ensure there are no cracks in the foundation, if there are they have to be parged in. Then a rubber substance is added, there are various products for this. Then the weeping tiles are added. Then clear stone and sand.

I recently got mine redone. Some pics here.

If you happen to have access to an excavator and dump truck you can probably do it yourself otherwise there's no point in renting all that, it will cost you almost as much as getting a pro, and with a pro at least the work is guaranteed and they have insurance if something goes wrong (ex: accidentally smash excavator into house).

That right there is what the guy I talked to on the phone said he needed to do to fix it PERMANENTLY, he said if this is done you won't need a dehumidifier or anything, pretty much your shit is sealed. My house is 4 times larger than yours, he quoted me around 60K to get it done, He pretty much told me that the price is ridiculous and he knows I'm not going to do it and starting talking other cheaper options.

 

[BoomerD]

To do it properly it has to be done from outside. It's not cheap. Basically need to ensure there are no cracks in the foundation, if there are they have to be parged in. Then a rubber substance is added, there are various products for this. Then the weeping tiles are added. Then clear stone and sand.

I recently got mine redone. Some pics here.

If you happen to have access to an excavator and dump truck you can probably do it yourself otherwise there's no point in renting all that, it will cost you almost as much as getting a pro, and with a pro at least the work is guaranteed and they have insurance if something goes wrong (ex: accidentally smash excavator into house).

Yep. The BEST way to keep water out of the basement is to stop it before it gets to the basement. RS did the job right. It's not cheap to go back and retrofit this kind of thing. It SHOULD be done during the construction of the house.

 

[sdifox]

we dug (yes shovel) a 6' trench on the side of the house, applied tar and tar sheet to the outside wall.

We knew where the problem area was, so we just fixed that part. We covered oh, about 10' section.

Call utils before you dig.

 

[MagnusTheBrewer]

Yep. The BEST way to keep water out of the basement is to stop it before it gets to the basement. RS did the job right. It's not cheap to go back and retrofit this kind of thing. It SHOULD be done during the construction of the house.

That is the best way but, also the most expensive. The foundation and slab CAN be sealed on the inside but, it means tearing up the basement and isn't cheap, just not as expensive as excavating around the foundation. Basically, it's the same process. Waterproof mastic with embedded rubber membrane and foam over that.

 

[SparkyJJO]

Ouch. Step one, never buy a house with a basement without a sump. For sure start with the dehumidifier. Hopefully you can get it in a good location near a drain and have it run whenever it needs to. Be sure to get the kind that will kick on and off depending on humidity.

My parents' house has no sump and no need of one. They do have a dehumidifier to keep humidity levels down but a sump wouldn't fix that kind of thing anyway.

Same with my brother's house. No sump, no need. He actually doesn't even need a dehumidifier either.

 

[steppinthrax]

we dug (yes shovel) a 6' trench on the side of the house, applied tar and tar sheet to the outside wall.

We knew where the problem area was, so we just fixed that part. We covered oh, about 10' section.

Call utils before you dig.

Where are you getting the tar from?

 

[Red Squirrel]

That right there is what the guy I talked to on the phone said he needed to do to fix it PERMANENTLY, he said if this is done you won't need a dehumidifier or anything, pretty much your shit is sealed. My house is 4 times larger than yours, he quoted me around 60K to get it done, He pretty much told me that the price is ridiculous and he knows I'm not going to do it and starting talking other cheaper options.

Ouch yep 60k sounds about right, it cost 14k for me and I did not get the front and one side done. It's L shaped so basically got 4 walls done.

In the older days they used to use thin layer of tar and clay tiles, and backfilled with whatever they had, so that's why after a while the seal starts to go, and overall the system does not work that well. In my case the ground was almost all clay which did not help things either. In spring if we happened to get a huge downpour of rain when there was still a few feet of snow left on the ground, the water would just slip right between the wall and ground.

 

[steppinthrax]

Ouch yep 60k sounds about right, it cost 14k for me and I did not get the front and one side done. It's L shaped so basically got 4 walls done.

In the older days they used to use thin layer of tar and clay tiles, and backfilled with whatever they had, so that's why after a while the seal starts to go, and overall the system does not work that well. In my case the ground was almost all clay which did not help things either. In spring if we happened to get a huge downpour of rain when there was still a few feet of snow left on the ground, the water would just slip right between the wall and ground.

To be honest it looks like something you could do yourself, if you rented a backhoe and simply dug up around your house, the rest is trivial. Getting the appropriate sealants would be next...