Water Getting Into Your Basement? Your Eavestroughs May Be the Cause

A wet basement often begins at the roof edge. This guide traces how eavestroughs send water to the foundation, how to test whether yours are the cause, and which outside fixes to try before you spend money on inside repairs.

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How a roof becomes a basement problem

One millimetre of rain on one square metre of roof, measured from above, is one litre of water. Picture a 100 square metre roof in a 10 millimetre downpour: about 1,000 litres arrive at the eaves. Those numbers are only an illustration, but they show the scale. Every litre either leaves through the downspouts and lands somewhere sensible, or ends up next to your foundation.

Water dumped beside the wall soaks the backfill, the loose soil packed around the basement after construction. Saturated soil pushes water toward the footing and looks for a way in: hairline cracks, the joint where the floor meets the wall, a window well, or a pipe penetration. A trough that overflows in a spring rain does the same thing along its whole length, since the spill falls straight onto the soil at the wall.

Play detective before you dig

Three questions narrow the field.

• When does it leak? Water that shows up during or just after a heavy rain points to roof water or surface drainage. Water in March during a thaw points to melt. Water in dry weather points somewhere else entirely.
• Where does it show? Note the wall, the corner, the window well. Write down which downspout or trough is directly outside.
• What is outside at that spot? Look for a downspout that empties within a metre of the wall, a low patch of ground, a sunk splash block, a trough that overflows above it, or a window well that fills like a bucket.

Then try a hose test in dry weather. Run the hose into the suspect downspout for a few minutes while a helper watches the wall inside. Stop as soon as water appears. If it never does, roof water may not be your cause.

Fix the water outside first

1. Clean the troughs and flush every downspout. A clogged outlet is the quickest way to turn one downspout's water into a curtain at the wall.
2. Lengthen each discharge. Many guides suggest carrying water at least 1.8 metres (6 feet) from the foundation, onto ground that slopes away. The downspout extension guide lists the options.
3. Restore the slope of the soil. The ground next to the house should fall away from it. A commonly cited rule of thumb is about 15 centimetres over the first 3 metres (6 inches over 10 feet). See grading soil around a foundation.
4. Deal with window wells. Keep them clear of leaves and soil, and check that the base can drain.
5. Check any underground connection. Some older homes tie downspouts into buried pipe. A blockage or overload can send water back toward the house, and a drain specialist can trace it. Our guide to underground downspout drainage explains the trade-offs. Check your municipality's current rules about connections before you change anything.

When the eavestroughs are not the cause

Eavestroughs are one cause of wet basements, not the only one. If you have fixed the outside water and still see moisture, consider a high water table, a failing sump pump, cracked or settled walls, a leaking pipe, or condensation on cold surfaces in humid summers. A waterproofing contractor or plumber can tell these apart, and it pays to get a written diagnosis.

Take these steps at once if water is entering:

• Stay out if water is near outlets, an electrical panel or appliances, and call an electrician.
• Take dated photos before cleanup.
• Call your insurer or broker. Coverage for water entering a basement varies by policy, so ask before you assume anything.

What a crew can and cannot do

A cleaning crew can clear troughs and flush downspouts, which removes the most common eavestrough cause. It cannot fix soil grading or a cracked wall. D&D Home Services offers gutter cleaning across Kitchener, Waterloo, Cambridge and Guelph, and quotes are free and confirmed in writing before work begins.

If water is already inside, deal with safety and documentation first, then work outward from the roof edge to the ground, and only then consider interior waterproofing.

Devon Moore, Operations Lead Co-Founder & Operations Lead, D&D Home Services

Devon Moore is the co-founder and Operations Lead at D&D Home Services, with hands-on experience cleaning hundreds of homes across Kitchener-Waterloo, Cambridge, and Guelph.