Someone asked me this week when they should plant their garden. That got me thinking about landscaping and how it can affect the integrity of a building. I thought this would be a good time to talk about some landscaping concerns that you could look for as you plan your spring gardening chores.
Poor landscaping designs can lead to wet or saturated soils around a building’s foundation. If you allow water to sit around the foundations there is a high probability that it will find its way into the basement,crawlspace, or into the walls. This is the most common cause of damp or wet basements. The most common landscaping problems I see are a reverse slopes and the grade being too high on the walls.
A reverse slope is when the ground slopes back toward the house instead of away. Patios and sidewalks often settle and create reverse slopes as well. Since water flows downhill, if downhill is towards the house then the rain water, roof run-off, or irrigation water is going to find its way to the foundation. Ideally the ground should drop one foot in the first six feet as it slopes from the house. Flat is not good either because it does not promote drainage of water away from the building.
When the grade is too high there is not enough distance between the soil and wood construction materials. There should be six inches of clearance between earth and wood. I have seen damp soil graded six inches above the bottom edge of wood siding. That’s a recipe for serious damage to both the siding and the wall structure under it.
Another way for water to get from the soil to the structure is through the concrete foundation. Concrete will wick water up into the wood wall material. I have concrete retaining walls, and when the soil or concrete slab at their base is saturated, I can see the moisture wick up the walls three to four inches. Water wicks twice that in my concrete block walls.
Heavy plantings against the base of the wall will restrict air circulation. This will reduce the ability of water to evaporate as it wicks through the concrete. Heavy watering of the plantings will intensify the problem.
If your wall coverings are stucco, masonry, fiber cement, or vinyl siding, and you think you can ignore or compromise on these standards, think again. Remember, under those rot-resistant coverings is wood sheathing and framing material. Your walls could look great on the surface while they are being compromised internally.
Here are some other areas to investigate. Check under decks. Backfill against a foundation will generally settle over time and can leave a substantial depression in some cases. This is a place that is easy to forget, especially if there is skirting around the deck. Check the base of wood support posts for decks and porches. Often the concrete footings were set at ground level or landscaping material has been raised over the base of the wood post. It is common to find rot in the base of these wood posts. Check the bases of wood steps. The wood stringers that support the steps are often on a poorly drained hard surface or on soil. Keep debris from building up around the base of steps as it will slow the drying of the wood between wetting events. Follow these suggestions even if you are using pressure treated wood. It may rot slower, but it will eventually rot like untreated wood.
There are a number of ways to end up with poor landscaping design. There are also a variety of ways to fix the problems. If you check your garden and find any of these problems, I suggest you make plans to correct the design and protect your home. Consult with a qualified landscape contractor for solutions if you are not sure how to proceed. I hope you enjoy your garden and a problem-free home.
If you have any questions about this topic, other aspects of a home inspection, or would like to book an inspection, please contact Bob at InspectionPro. My email address is [email protected] and I can be reached at 250-212-5490.