Dear Mr. Marantz.
We have a 40-year old bungalow in Fort Richmond. Overall it is in good shape. Below the front steps there is a cavity of 60-70 cm depth. I have received conflicting advice (from non-specialists) as to whether I should pour sand in the gap. Some say yes, to avoid water leaking through the basement wall. Others say no, as it is needed for airing out any moisture that comes in by rain and lingers.
Your advice would be greatly appreciated. Thank you very much.
One of the main points that I stress to my clients during home inspections is the importance of grading and drainage in relation to the overall quality of the home. Regular maintenance of proper grading around the foundation can make a world of difference between a dry, comfortable basement and a damp, musty space. Ensuring a proper slope of soil away from the foundation along with downspout extensions will help prevent moisture intrusion through basement windows and small cracks or openings in the foundation. The area under your steps should be included in this regular maintenance.
Any time there is a large depression in the soil surrounding a home, there may be a concentration of moisture in this area from heavy rains or snow melt runoff. This can be observed in any area where there is uneven grading. This is what can be observed in the numerous “potholes” that can be seen in farmers fields in rural areas. Our clay soil can only absorb a limited amount of moisture, and the excess will run off to low lying areas. This is what can happen in the area underneath your front steps. If the foundation in this area is not properly damp proofed or has small cracks or holes, leakage is almost a certainty. That is why attention to this area is very important.
The ideal solution to your problem is to fill in this area with the same clay that surrounds your home, but this may prove difficult. It may be very hard to get the dry clay broken up sufficiently to fill the void, without gaps between the clumps. Clay is ideal, because it will have the same properties as the rest of the backfill around your home in that it will only absorb so much water and may help prevent the “pothole effect” under your steps.
Sand may be the easiest fill to use under your steps, but is not ideal. Sand can be quite porous and may not prevent excess moisture from running to this low area, but will be better than the status quo. Clean crushed stone or river wash stone, both readily available from landscaping suppliers, will also be easily shovelled under the steps, but may have the same problem as the sand. If clay is not readily available or too difficult to work with, there may be another reasonable alternative. Crushed limestone known as “3/4 down” or “1/4 down” may provide a better fill than sand. This material contains granules of different sizes and will compact quite well when damp. It is easy to pack into small areas, like that under your steps, and will resist some moisture intrusion. Once the area under the stairs is filled to grade with this material, a clay or topsoil cap should be shovelled on top of this fill to help with grading and prevent absorption of rain and snow melt.
There is also a second reason, other than foundation seepage, to fill in the area under the steps. Pest intrusion in areas like this has been quite common in the last number of years. Rabbits, squirrels, mice, as well as bees, hornets, and wasps love to build nests in areas like that found under your steps. While the rodents and rabbits may cause little trouble outside the home, their droppings can be quite a nuisance and their proximity to the home will allow easier access to the living space if the opportunity presents itself. Mice require very small gaps for entrance into homes and they have been quite a problem in recent years. Allowing them a nice sheltered area to nest outside the home is an invitation to warmer winter climates inside.
Bees, hornets, and wasps can be a safety hazard to inhabitants if they are allowed to build nests under stairs, decks and under eaves in homes. This is a particularly large concern if any of the occupants of the home are allergic to stings. Filling in the void under the stairs will prevent these flying insects from coming back.
Despite the best intentions of your “non-specialist” advisers, they are flat out wrong. You should never leave depressed areas open for airing out, but should fill them above grade to avoid moisture intrusion, in the first place. I agree that wooden steps and decks built above grade should have openings or vents to allow the material to dry after wetting, but this is not your situation. Concrete stairs are designed to sit on grade for years without moisture damage. Filling in the area underneath that has worn away with normal soil erosion is critical to maintaining a dry and healthy environment inside and outside the home.