Drainage

Table of Contents

Everything is Wet

Before I bought a house, a house's relationship with the environment seemed pretty simple.

On the one hand, you have Mother Nature, with a complex ecosystem where every rock and tree is part of the whole, and everything decays and regenerates over time.

On the other hand, you have a house made by people. As a man-made object, it is independent of mother nature, and stands until disaster or renovations take it down.

Of course, now that I own a house, I realize that's completely naive. A house is just as much a part of the environment as a rock or a tree, and Mother Nature is constantly trying to break it down just like everything else. Classic entropy .

I always worried about termites or ants or ambitious moles . But in fact, the main danger (and annoyance) to most houses is drainage. I've found that most people who build houses (or other structures) usually forget this completely.

For instance, in my last house, a previous owner had build a beautiful large carport with a small storage shed attached. It was spacious, elegantly and sturdily constructed, and was one of the reasons I bought the house. However, I quickly realized that the carport was more of a liability than an asset. Why? Because whoever built it hadn't paid attention to drainage at all.

The carport was built right next to a large slope. When it rained, water would run off the slope and into the carport. The broad concrete surface of the carport was perennially wet. Furthermore, the pressure of the wet and moving soil was pushing against the carport wall, causing it to buckle.

It turns out the builder hadn't thought about drainage at all. I had two options: either retrofit the entire structure with proper gravity-fed drains (and reinforce the carport wall) or rebuild it entirely. The costs weren't terribly different.

My second house had a proper garage. However, I soon found out that the entire basement flooded whenever it rained. Again, the house was on a slope. Water would run off the slope to the sides of the house, and come off the roof, and promptly enter the basement.

I had to redo the drainage around the house, and replace all the flooring in the basement. Ouch.

Okay, maybe I just got unlucky. But one of my neighbors has a new house, which also has serious water run-off problems from a nearby hillside. It's a new house, and the builders didn't provide for drainage of rainwater coming off the hill.

And it's not just houses. The parking garage where I work (downtown Seattle) has large puddles form on all floors when it rains. This is Seattle. It rains all the time. Parking garages are simple structures. How could someone build a parking garage in Seattle that allows water to pool when it rains?

Maybe People Who Build Things Are As Stupid As Me

Well, maybe the people who build houses are as stupid as me? I didn't think about drainage before buying a house, maybe they didn't think about drainage before they built one.

Even a short investigation will show that's not an excuse. Drainage isn't something unusual when building a house. It's fundamental. If someone has even basic training in construction, drainage is a known issue.

The Romans knew about drainage. Until I wrote this article, I didn't know Plumbing World existed, but it does, and it has a brief history of the debt that modern plumbing and drainage owes to the Romans. Even pre-Roman (or pre-Greek) cultures like the Minoans had basic drainage. They've found evidence of clever drainage in Roman forums at Pompeii and at a Roman villa in Whitehall in the UK.

From the Whitehall dig: the house was built on a grid pattern of culverts.

Basically, people have been getting drainage right since before Christ. The solution is pretty simple: have a system of gravity-fed drains and pipes to direct rainwater and other runoff away from the house, so that the foundations and interior stay dry.

Pretty basic.

But again, since before the time of Christ right through today, people keep screwing it up.

There isn't any excuse for builders in the 21st century to screw up drainage. It's a 1st century technology.

Getting it Right

Based on my experience with houses, drainage is something I'll look at pretty closely during my next home purchase. It's usually obvious when you look at the property and structure where rainwater will go, and there should be simple gravity-fed drains that carry the water to the sewer or somewhere else safe that won't erode the property or flood basements.

But the parking garage really confuses me. Just as it is easy to redirect rainwater for houses, it is even easier for parking garages. Just tilt the floors! I saw this first at a parking garage at Carnegie Mellon University . The floors were slightly tilted, so water could never pool. The tilt was very subtle, but effective.

Every parking garage in Seattle should have tilted floors. I'm not aware of a single one that does.

Appendix

A random side-note: while searching for examples of "ambitious moles" on the Internet, I hit upon an Indian Astrology site (!). Apparently, having a mole on your butt means you are un-ambitious. So you learn something every day.