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October 10, 2018
"It's raining hard out there. I should check the basement. Oh, good golly!" Sound familiar? Is there really any such thing as a waterproof basement?
On our first visit to our current home five years ago, it was clear that the basement flooded regularly – up to three (3) inches several times each year. The house was constructed in 1942 and included an evolving series of sump pump wells. We took on the challenge to make this home dry. Here, we discuss how we are winning the battle!
This is not an exhaustive list of dry-basement strategies but will inform your efforts to control water on your property. There are many strategies out there, but these methods have worked very well for us in Mount Washington, Maryland. They are relatively low-cost, but some are labor-intensive. Professional landscapers, civil engineers, plumbers, and other trades can help.
Here are some ways to prevent water from reaching your house, to keep your basement dry.
1. DRAIN ROOF RAIN WATER AWAY: Annually, do a check to determine where your roof’s rain water goes. All gutters should be secure - not bowing down in the middle. Rain should drain directly into downspouts even in the strongest rain. Sometimes, gutters and downspouts must be increased in size. Downspouts are best that discharge into “rain leaders” - pipes in the ground that discharge downhill or at street curbs. You can test a rain leader by lifting off the downspout and running a hose in the ground leader. If it fills and overflows, this pipe needs work; to clear or repair a broken pipe. If it keeps accepting hose water, go and find where it comes out. Downspouts MUST NEVER dump next to foundation walls. Continuously wet basement walls can soften supporting soils causing structural cracks, drafty rooms, and a wet basement.
2. SURVEY SURFACE SOURCES: Look uphill at the land, paving, and other roofs sending rainwater your way. Don a rain suit and waders to walk these areas in moderate to hard rain. Print a map and outline your uphill rain field. Define your problem.
Our new home received rainwater from three properties, four house roofs, and an alley. More than an acre of rainwater (!) gushed straight towards one of our basement windows, flooding even in moderate rain.
3. DIVERT: Make a diversion path so the rainwater misses the house. We dug a continuous trench; it is horseshoe-shaped, on three sides of the house, a minimum of one foot deep, and has an even-sloped bottom. The trench overflow goes safely into the front yard. At the bottom of the trench, place one, or more, drain-tile pipes in the bottom - ensuring an even, low slope out to the discharge. Extra drain pipe ensures there is void space where water can flow out. The trench picks up “Y” piping connections from each downspout and each susceptible window well. It also accepts the sump pump discharge. The drain piping runs out to the discharge. In my system, I could run a snake into one front yard discharge pipe, run it in around the entire house, and have it emerge in the other end front yard discharge.
To construct the surface drainage intercept trench, first temporarily remove the porous top soil next to the basement walls. Remove plants and topsoil, if any, onto a tarp, and then replace on the finished slope. Soil removed to make the trench is shoveled against the basement walls, and then compacted into even slopes back down to the trench edge. Drain tile is placed in the bottom and the drainage slope is confirmed. Perforated plastic drain pipe is staked on the trench bottom and hose-tested for quick drainage from anywhere to the front yard.
Then, the trench is filled with chip stone or round gravel, no fine stones, allowing surface water to drain down fast. Grey chip stone path shows around the house along with some areas covered with pavers. This is truly a permeable walkway and perimeter defense against water approaching your basement walls.
4. LAWNS TO TERRACE GARDENS: Lawns let water flow fast, causing floods. Slow the flow and absorb the water by converting lawn turf to gardens. Digging a swale and mound (also referred to as a berm) across contour creates a green terrace capturing water and creating lush gardens with little to no sprinkler needed. For newbies to this concept, a swale is basically a ditch with closed ends. “On contour” means that both sides of the swale are level so that all the collected water stays put and has time to be absorbed into the soil. As soil amendments build rich humus and microorganism, and perennial roots take hold, water capacity increases dramatically.
We began converting lawn terrace gardens by hand digging swales creating berms parallel to slope contours. Now the volume of water approaching our house is reduced or eliminated. To reduce street flooding, we constructed a rain garden in front with help from Bluewater Baltimore, our neighbors, and friends. Now our massive rainwater outflow is a green, wildlife resource.
5. SEAL THE VESSEL: Basement walls sometimes get wet or allow water flow. We had one vertical concrete crack five years ago that seeped water. We used an “epoxy injection kit” to prepare and seal this crack. After five years, we now have one very small void to inject again. UPDATE: This small void at the floor was leaking freely in a week of summer downpours. I shop vacuumed (wet/dry vacuum) morning and evening.
For damp walls and floors, we use a product called RadonSeal® and DRYLOCK® Extreme Masonry Waterproofer. (Wait for the driest season with the dehumidifier running to use the products. You can heat the surfaces to remove moisture, too). RadonSeal goes on like clear water, soaking brick, concrete, and mortar joints and penetrating up to two inches deep. It fills the air voids left by water, then cures and seals permanently. Two quick coats to be thorough and you may never need to apply it again! By the way, RadonSeal reduces radon gas, too.
6. DEHUMIDIFY YEAR-ROUND: We have an ENERGY STAR dehumidifier model, which is endorsed by Consumer Reports. It is elevated to drain into the laundry tub. We monitor and set the humidity level higher in the summer and lower in the winter. It cycles on year-round keeping everything relatively dry. Bonus: We line-dry laundry, saving dryer costs. Plus, anything wet - from shoes to electronics - gets quickly and thoroughly dried just hanging above the dehumidifier.
Add these steps to your "To Do's" as soon as possible to ward off a wet basement. Stay dry out there!
Adapted for the BPI Homeowner Blog from the Mt. Washington (Baltimore area, Maryland) newsletter.
P.S. Frank Lee and his neighbors experienced one of the highest rain-week accumulation in recorded history. Basements, never damp before, are now in a wetland - many damp and some flooded for five days straight. Right now, people are identifying active springs in their lawns and patios.