How High to Run Basement Wall Waterproof
I am building my own workshop. It is built into a hill so the back walls will be below grade. Backfilling is coming soon so I need to get some waterproofing put on.
My question is how do people decide where to stop the waterproofing for good aesthetics? Finished grade will slope along the wall so I don’t have a fixed elevation to shoot for. Do you folks try to finish a set amount above finished grade – in which case the wonderful black treatment will be visible (The neighbors will love that… I don’t imagine the waterproofing will hold paint)? Or do you aim for a bit below grade and hope that the small area not waterproofed won’t have enough static pressure to push water through? The wall (ICF – Rastra) will be stuccoed eventually.
Your thoughts and rules of thumb are appreciated.
Thanks.
-dch in the Arizona Desert
Replies
I ran the ugly black waterproofing to abut a foot below frade, then ran the drain plane from footing drain to grade.
For a drain plane, I emplaced a foot thick band of clean 1" gravel. An advantage is that I don't have to edge the yard when I mow.
SamT
A Pragmatic Classical Liberal, aka Libertarian.
I'm always right!
Except when I'm not.
Black waterproofing sticking out above grade looks awful - especially if it is unintentional and haphazard. Carefully establish finished grade levels and waterproof up to a foot below it. If you are uncomfortable about that last foot I guess you could use Xypex on that bit, but really as long as the finished grade slopes away from the foundation it isn't necessary.
6" above final grade is rule of thumb here.
If by "waterproofing" you mean the thin asphaltic dampproofing that's quickly sprayed on before backfill, then you may want to consider having a real waterproofing job done while the wall is open. Dampproofing won't prevent leakage through the inevitable crack in the concrete. A 60-mil sprayed film or peel/stick membrane will bridge small cracks.
As to appearance above grade, you might consider applying the waterproofing to above grade plus a sheet of something applied from just below grade to the sill, much as is done when running exterior foam insulation from footing to sill, for protection against UV damage and other injuries to the foam.
Thanks all for the suggestions.
Dick brings up a related question - what should I use for waterproofing.
The wall is made from Rastra which is the giant ICF blocks made from styrofoam pellets and concrete slurry. This stuff is semi permiable. The ground water content in the Arizona desert is..., well, not much of a considertion. However, we do get out summer monsoons which can drop an inch or two of water (about a third of our anual rainfall). I have an open trench so I figure it is much easier to waterproof now than wish I had later.
With that in mind, I don't know that I need to go to the levels folks do in other parts of the country. I have done most of the work on this project myself. Not sure if this is something I should tackle, or if the "mess" factor makes it something I should hire. Henrys makes some sort of product that uses their black goo and a cloth / membrane you embed in it.
Thanks again.
-dch
What does Rastra say to do? I've never thought of what people using ICF do for below grade waterproofing. I would think the ICF manufacturer would have some recommendations about water proofing.
The soil is "BONE DRY"! Most people don't deal with this because basements are virtually non-existant in the Phoenix area. The soil here is plauged with Caliche clay which often requires a hammer/breaker on a hoe to dig in. 99% of construction here is monolithic poured slab on grade. If there is rain, we get flash floods because water does not soak in.
My lot is sloping so I had to either dig in, or haul in fill. The fill option - although much cheaper in hind sight - would have raised the finsished floor six to eight feet. That doesn't work too well with the level of the house and driveway. Also it was an attempt to be neighborly and not block their view. But not good deed goes unpunished... They officially let me know I have ruined their whole life. But that's another story.
The salesman for the Rastra product built his home on a sloping lot also. He used the Henry's product I mentioned. Not sure which it was, but it included the goo and some sort of membrane you embed.
I can probably get away with no waterproofing at all. But the trench is open so easiest to do now. I did install a foundation drain at the footing. Any thoughts on a good drainage plane product? I have seen the fancy dimpled pads. But in my case wouldn't a layer of washed gravel next to the wall separated from the soil with some filter cloth work?
Thanks again for your input.
-dch
Here are a few shots. The backfill will be about 6 feet high and taper to about 3 feet.
Same soil here in the desert in SoCal ... Caliche. Problem w/ the basement is that w/ the clay and when it rains hard ... the basements can be the low point. Not in your case. I'd make sure I put in some good drain tile so that it diverts quickly around the house to the 'front', too, maybe. I think you did the right thing w/ the view thing. Around here they build everything up, too. I'm contemplating building ... and my options.
Isn't this getting a bit complicated for a workshop in Arizona? Full waterproofing and some unspecified covering for it above grade? I wonder what all the houses in his area have and whether they experience any problems.
I missed the note about AridZona. The OP knows what he has to deal with, and whether waterproofing vs dampproofing is needed for a workshop. I suppose if the soil is damp enough to warrant something to retard inward diffusion of moisture, then at least thinking about waterproofing is worth investigating the cost difference vs. benefit. But if the soil normally is bone dry where he is, that's another thing, and then I would think that dampproofing just to grade line would do it.