how to fix negative grading

Nice house soil grading If water runs towards or pools next to your house's foundation walls you likely have some house grading issues. Water tends to run downhill, on the top of the ground as well as below the surface. When a home is placed on a lot, consideration should be given to the path water will take. Allowance should be made for water to run away from the building or more specifically, away from the foundation. This is true regardless the type of home, whether on a slab, crawl space, basement, even if on piers, proper drainage necessary for several reasons.

Proper grading is also important regardless the type of lot. It doesn't matter if a home sits on a flat lot, slight slope or mountain side, rain water from the roof, and rain water that builds up on the ground surface needs to be properly directed away from the foundation of the home. Of course if a home is at the bottom of a very large steep hill, extra care may be warranted.

Some Home Grading Terminology:

Positive Grade or (Good Soil Grade) – when the ground surface slopes down and away from a building. This is what good and what you want for proper drainage, but often can be improved.

Negative Grade or (Poor Soil Grade) – when the ground surface slopes towards the building. This is bad and contributes to excess water puddling against or soaking into the foundation walls. This is a major contributor to foundation deterioration and settlement issues and should be resolved as quickly as possible.

Level Grade – when the ground surface is level or flat. This condition should be corrected to positive grade for proper drainage around the home. This is sometimes easily accomplished by raising the soil level next to the foundation walls around the perimeter of the home.

High Grade or "Siding too close to grade" – when the ground level is too close to the siding it presents conditions for moisture damage to the siding and wall structures.

Settled Grade – this occurs when the soil that was back-filled next to the foundation walls settles downward. The soil grade is positive when the house is sold and over the next 1 to 3 years typically the soil will often settle creating a negative grade in some or all areas around the foundation walls. This is usually remedied by adding additional soil. The building contractor should be contacted and will usually do this job for no charge since it is usually covered by warranty and is due to improper back-filling procedures. Since this condition gradually occurs it often goes unnoticed by the homeowner and is not addressed until the home is inspected by a home inspector.

Siding too close to grade

Proper soil grade allows for 6 inch minimum clearance between soil and bottom of siding to prevent moisture damage.

"Siding too close to grade"

This is often times cause by homeowners piling up mulch over the years, adding more and more much until it piles up too close to or against the siding. Water can splash up from the ground onto and behind the siding, or in the case of much piled up acts as a giant sponge that can transfer moisture to the wood components vulnerable to rot. When siding is too close to grade, it should be corrected as soon as possible.

Water puddled at corner due to negative soil grade and missing downspout extension.

Roof Water, Gutters and Downspouts

Now, even if the grade is correct the water running off the roof can wreak havoc on the foundation if it is not also properly directed away from the foundation with downspouts and downspout extensions. Downspouts should direct roof water at least a few feet and preferable 5 to 6 feet away from the foundation. Proper grading will ensure that the downspout discharged water flows away from and not back towards the home. See my post on Roof Water Drainage.

Consequences of House Grading Issues

Water drains towards house or puddles at foundation walls causing moisture related issues
Wet, damp, musty or moldy basement and or crawl space
Flooding during times of heavy rain fall
Deterioration of the foundation walls
Foundation settlement that results in cracking foundation walls and floors
Structural Damage due to settlement and deterioration

The above list highlights some of the reasons for quick action to repair improper grade issues. The longer the problem goes unchecked the greater the likelihood the damage and needed repairs will be greater.

How to determine your grade?

You will need a 4 or 6 foot level or a straight 8 foot board using a 1 to 2 foot level to easily determine the slope. A general rule of thumb is for the grade to slope downward and away from the building at the rate of about 1- inch per foot for the first 6-feet. I rarely see this with any home but this would be ideal grade on a perfect lot. Hopefully your grade is sloping down, away from the house at least a little bit.

A Few Home Soil Grading Points:

During a home inspection, when deep snow is on the ground, it's nearly impossible to determine the grade of soil around a home.
Most new homes end up with significant negative grade after the house if built, due to settlement of soil that was back-filled at the outside of the foundation walls; such negative grade should be taken care of by the builder at the 1 year warranty, but if the homeowner does not ask they will usually skip it.
Beware of mulch around the foundation, it can be deceptive in promoting what looks like a positive or proper grade of soil. Remember mulch sits on top of the ground surface. One of the functions of much is to retain moisture, think – "giant sponge". You do not want mulch to close to or touching the walls, try to maintain a 6 inch minimum clearance between bottom of wall and top of mulch if possible.
Simply adding mulch to raise the soil level to improve the grade is not sufficient, it the level of the soil under the mulch that determines the angle of grade. The mulch is just like a big sponge sitting on the ground.
If sufficient grade can not be easily attained on your property, consider consulting a landscape professional for the best options. The use of buried drainage pipe(s), swale(s), French drain(s) and more may do the trick, individually or in combination.
The size of the soffit overhang can play a factor on many homes in a positive or negative way. The larger the soffit overhang the better as for getting roof water away from the foundation.
The type of soil or ground cover around the foundation also can play a significant role. Some soils drain like a sieve and some hold water like a pool liner or a sponge. The root system of established grass forms a great barrier to keep surface water up on top of the ground and draining away from the foundation walls, in contrast to gravel or mulch in which the water runs straight down through.
Water tends to form drainage pathways. If roof or surface water has formed a pathway down the side of your foundation wall possibly and into the basement or under the foundation (wet or damp basement, or settled foundation condition) that becomes its preferred route unless you make significant changes to re-rout the water, such as improving the soil grade, adding or improving the gutters and downspout extensions.