Here's why water is the silent foe to all foundations and what to look for and how to plan for drainage before it costs you.
Answer: The answer is that if water is allowed to pool around the foundation, it can wreak havoc on the foundation of a building. Clay soils expand, contract, and crack unevenly, leading to cracked walls and uneven floors, rusting steel, and damp walls. Most of these problems are avoided by a well-designed site with good grading, gutters, and French drains, which are all planned and budgeted prior to construction.
So, ask any building professional what is the leading cause of the destruction of most buildings, and many will say the same: water. Floods and earthquakes are not involved; it is simply water that has been in the wrong place for too long.
Once you know about drainage and how it can impact the foundation, you will be able to prevent cracked walls, sticking doors, damp basements, and repair bills in lakhs. How it works and what to do about it.
Why is soil so important to a foundation?
A building is not held up by a foundation. It transfers the building load to the soil below the building; the soil should be stable under the load of the building. Water affects soil properties. If drainage becomes inadequate, your building's ground is no longer predictable.
What are some problems that can be caused by poor drainage on a foundation?
• Swelling and shrinking of soils. Clays tend to swell when wet and shrink when dry. When it rains on one side of a building and not on the other, the soil will shift. This is called differential movement and is the cause of most foundation cracks.
• Decreased bearing strength. Soils that are saturated are weaker soils. A footing that remains wet cannot support the same load, and the building slowly settles. Where the soil is sandy, it can be difficult to keep fine particles in place and to avoid formation of hidden voids under the foundation.
• Hydrostatic pressure. Water in the soil around a basement or foundation wall exerts actual pressure against the wall. Walls crack, bow, or permit water to seep through joints. Slabs may also be driven upwards from beneath.
• Frost heave. Soil water freezes and expands in cooler areas, causing the foundation to be lifted. The closer the water is to the footing, the worse.
• Moisture damage and corrosion. The steel reinforcement in concrete is constantly wet. The rusting of the steel causes it to expand and crack the concrete. Other symptoms include mold, musty odor, and white mineral deposits on walls.
What are the indications of drainage issues?
The onset of foundation issues doesn't happen overnight. Watch for:
• Sloping or stepped cracks in walls
• Sticking or unclosing doors and windows
• Floors that slope or are uneven.
• Pooling water around the building after a rainstorm.
• Musty odors, mold or damp spots inside the house
• Space between walls and floors or ceiling
In some cases, the hairline crack is a non-crisis situation. If cracks continue to progress, or several of the above symptoms occur at the same time, it is time to consult a structural or geotechnical engineer
What is a well-draining foundation?
The majority of drainage issues can be avoided. A well-planned system typically will include:
• Adequate grading: The ground should be sloped away from the building. Generally the rule of thumb is approximately 15 cm of fall over the first 3 meters.
• Roof water accumulates quickly—gutters and downspouts. Place it at least 1.5 to 3 meters (or more) from the foundation.
• Perimeter (French) drains: A pipe with a hole in it that is installed in gravel surrounding the footing to collect water from the ground and remove it ahead of pressure accumulation.
• Waterproofing: Below-ground walls are covered with membranes and coatings, which provide an extra line of defense.
• Sump pumps: A sump pump is used to keep basements dry in areas where there is a high water table.
• Smart landscaping: Avoid large trees close to the building, as they extract moisture from clay soil, which results in shrinking of the building. Try to prevent water collecting within garden beds next to walls.
• Prevent plumbing issues: A pipe leak can flood the ground as well as the monsoon, so fix leaks promptly.
What is the best time to plan drainage?
Before construction begins. Drainage is an after-thought, too often. When the time comes to repair it, it will involve digging, disruption, and a lot more expense.
A smarter sequence is like this:
• Study the site. Determine soil type, depth of water table, slope, and local rainfall. A geotechnical investigation provides you with fact, rather than assuming.
• Select an appropriate foundation. Match its type and depth to the soil and moisture conditions.
• Design drainage in conjunction with the structure. Grades, drains, waterproofing, and outlets should be included in the drawings from the first day.
• Take into account the cost while budgeting. People rarely take this step.
This is even more important in areas of high monsoon precipitation, such as most of South Asia. A good building in a dry season may turn to crap in a wet one.
Why is it important to estimate costs accurately for drainage?
Drainage and waterproofing are no trivial expense items. These all cost money and will add up when excavating, adding gravel, installing perforated pipes, membranes, sump systems and additional labor. They are hidden when they are not part of the original budget and will be included in the unexpected budget. Or they are chopped off to make money, and the troubles come back.
The following factors should be considered in a detailed construction cost estimate:
• Performances of materials such as gravel, pipes, membranes, and concrete
• Excavation and installation labor and equipment costs.
• The waterproofing and damp-proofing should be determined. Requirements for waterproofing and damp-proofing should be established.
• Factors that affect the cost of the site.
• Appropriate contingency plan for unexpected ground or water conditions.
Having the correct numbers will allow you to determine what to construct, how to construct it, and how much to save up before breaking ground.
Design Estimation offers construction cost estimating services for builders, contractors, and property owners. Our quotes include everything from the foundation to the drainage—things that are often easy to miss out on—giving you peace of mind when budgeting and helping you to avoid an expensive change once the work has begun.
Frequently asked questions
Can lack of drainage lead to foundation cracks?
Yes. Soil moisture can vary, causing soil to expand and shrink and exerting stress on the foundation and cracking it.
How far should water be allowed to run away from a building?
Located 1.5-3 meters or further from the foundation.
Are the foundations of houses that have to be drained costly?
This is a far cheaper alternative to repairing the damage to the foundation, and a detailed estimate can be helpful in planning for this.
Final thoughts
Water always finds a way, and your foundation must accommodate it. When it comes to building strength, good grading, well-designed drains, proper waterproofing, and a budget accordingly do the trick for decades of strength.
New building construction or renovation? Make sure you're on the right number right away. See for yourself the effectiveness of our estimation services on www.designestimation.com!
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