BASEMENT FINISHING COURSE VIDEO: How Basement Waterproofing Works

This video is all about the different strategies that are used to waterproof a basement

Now most basements won't have all these things going on, but I included them all in this illustration so I could explain them

and that's so you would understand. The first thing is this waterproof membrane

In this case it's a blue on the outside of the foundation wall

Masonry is not very waterproof on its own, need some kind of membrane to ensure that water doesn't get through. And that's what that membrane

is for. That could be a coating on the outside. Sometimes it's sheet material that's glued and sealed

to the outside of the foundation wall. But regardless of the details, the approach is always the same

and that's to make what's normally a porous wall, poured concrete, block, brick, and stone

They're all fairly porous. They might look solid, but they're not all that waterproof

So the membrane fixes that. And as long as it's installed properly, it's going to go a long way to help

But water is sneaky stuff, so you really do need multiple layers of engineering going on to help you

And that's what this black dimpled layer is all about. I've talked about this earlier in other videos, but it's a heavy plastic sheet material

with raised dimples on the inside face. And the purpose of this is to create a vertical drainage channels

so that any water that gets through here can drain downwards without the soil pressure forcing it in through the wall

Soil pressure can make water go horizontally through a foundation wall quite noticeably

So that the dimpled layer, although it's tight against the wall, these dimples keep parts of it away from the foundation wall

so that there is this unpressurized opportunity for water to drain down

And in this case, it's draining down into some weeping tile, which is a perforated, flexible pipe that's made to gather water

and the crushed stone around the weeping tile allows that water to move into the tile more easily

and the tile is going to empty out somewhere by gravity The outlet of it will be lower than the building and water can drain that way So this is kind of the standard way that a good basement is finished on the outside with the waterproof membrane

the dimpled foundation wrap, and then the crushed stone and the weeping tile

Now, there are other things that need to happen. This is a sump pump arrangement

You can have all of the materials you want on the outside

but if the water level, the groundwater level, periodically, maybe in wet times of the year, rises or wants to rise to a point higher than your basement floor

well, that's where the whole sump pump thing comes in, because what you're doing essentially is pumping that water out before the level rises in the soil

to the floor level. And as I've described in videos and other parts of the course, if you need a

sump pump pump to protect your finished basement, then you need two sump pumps. One, the regular

120 volt model, and then a backup sump pump. In this case, it runs off of a battery, so it can work

for a time when the power is out. And also if this main pump fails and the water level continues to

eyes, this battery powered pump will kick in and take over. So do not rely just on one pump

If you need a sum pump, you actually need two. I would argue you actually need four because you're

going to want to have these two in the sump working for you. And then you really should spend the

extra money and keep a couple of identical spares on the shelf so that you can swap them out

if need be in an emergency. It does cost a little bit of money, but it's

small potatoes compared with having your basement flooded, especially when it doesn't have to happen

Now, here's something I want you to look at here, this black pipe

This is part of a strategy that I've seen work quite well in drying out a basement

I've seen situations where leaky basements were probably leaking because this outside drainage tile wasn't working anymore

Maybe it was never even installed in the first place, or maybe it clogged with silt or something Old drainage tiles were made out of clay tiles and they can deteriorate and just stop working So one strategy is to install fresh weeping tile

but on the inside of the basement. So that's a big advantage because it means you don't have to dig

the soil away from the outside of your house, which is very expensive and disruptive

And in many cases, installing it here along the edge of the inside wall works quite well

You don't have to do any digging. You just have to break up the concrete in this area

Lay down the drainage tile with some crushed stone around it. And in this case, it's emptying into the sump

So what you're doing is really you're capturing the water from a larger area

In this case, it's this one wall. It could also connect into the other wall too

You're gathering the water that builds up there and then you're dumping it into the sump and the sump pump's going to move it up and out

This sort of drainage tile could just drain somewhere else too. It might drain into a floor drain right here or it could drain outside your home if you've got some

elevation to work with. But this is a strategy that works quite well

You break up the floor, you install the tile and the crushed stone and then you replace the

concrete and that can work well and save you a lot of trouble

Now over here, we have the main household drain. So this is the floor drain

And usually the floor, the concrete floor, has been sloped a bit so that water will drain into the drain

But this drain pipe here is also the one where all the sewage leaves your house

So there would be connections to this pipe somewhere else. And it would leave your home and take all the wastewater with you

Now, the problem and the issue that has to do with the dry. dryness of your basement happens when some backing up of a municipal sewage system occurs

And sometimes that can happen when there's a tremendous amount of rain in an area

Other times, if you live in a town or city where the sewage needs to be pumped up

when large quantities of sewage need to be pumped up and away because the town lives in a low area

and that pumping system fails well you going to get sewage backing up through this pipe and bubbling up through the subfloor or sort of through the floor drain

This happens to thousands of homes every year around the world, but it doesn't have to

And the way you stop it is early on in the process of finishing, you install here what's called a backwater valve

it's kind of like a check valve for sewage. So it allows the free flow of sewage out this pipe

It's typically four inches in diameter. But if there is a sewage backup because of heavy rains or a failure of the municipal system

the sewage can't go any further than the backwater valve. So this can be a significant level of protection for you because sewage in your

basement is a very nasty thing. It's going to require a complete rebuilding of your finished

basement, all for want of relatively inexpensive and fairly easy to install backwater valve

So these three elements, the outside your wall element, the inside drainage tile option

your sump, pump and equipment here, and then some protection for, sewage backups, these are the essentials that you're going to want to look at

You may not need all of them. I mean, if you have a bone dry basement and you don't have this stuff on the outside

then that's fine. But if you do need to do some remedial work, this is the kind of thing that you're going

to have to be looking at. One other thing before I finish up, and it's fairly simple, this is all complicated

gear underneath, and it may be hard to establish, but some basic

that you have to keep in mind is simplyитиats and eaves troughs

If you can shed the water well away from your house, then that's going to be easier on everything else

So sometimes a leaky basement is nothing more than a function of not having eaves troughs

or not having downspouts that lead that water well away, along with the proper grading of the soil around your basement

If you have a leaky basement, then eaves troughs, downspout, and surface grading of the soil is the first place you're going to want to look