Have you ever walked down the basement stairs of a house and gotten transported back in time to your parents dark, shag carpeted, wood paneled damp, musty teenage hangout? As a home inspector, this is a common occurrence. That damp funky smell, you know the one, is (primarily) caused by dampness as low levels of water seep in through weaknesses in the foundation wall or through the porous concrete itself. The water gets absorbed into the wall studs, drywall and carpeting causing mildew, moulds, rot and leaving a noticeable odour.
Many of the homes that I look at have water intrusion problems in the basement at some level of severity. These can range from the dampness and musty smell to trickling water and full puddles. Unfortunately for the prospective buyer, often at the time of the inspection, the basement is dry. The water leakage may be seasonal requiring the right conditions such as melting snow or long periods of heavy rain to reoccur. However, for a sharp eyed home inspector, the tell tale signs of water are there if you know what to look for. In some cases though, sharp eyes aren’t even needed. The damage is really obvious. Have a look at these photos to see what I am talking about.
The sometimes not-so-subtle signs of water entering a basement that I commonly detect are:
Foundation Wall Stains
Foundation or Floor Efflorescence
Rusting of Insulation Banding, Nails, Electrical Panel Components, or Carpet Tack Strips
Rot of Stud Wall Bottom Plate
Microbial Growth
Damp Walls (Detected via Stains or using Moisture Meter)
Spalling Foundation Wall Paint
So what are the major causes of these conditions? In most cases they are readily observable and fixable. Let’s discuss.
Exterior Grading
So simple, but critical and done wrong on many homes. Very simply, surface water runs downhill towards the home and it needs to run away from the home. If the house is the low point of the property, the water gathers against the foundation wall and if there are any weaknesses (cracks, etc) the water will run into the basement.
One common situation that I see in newer homes is where the builder digs a hole for the house and installs the foundation. Afterwards, the hole around the foundation is back filled with soil but it is not adequately compacted. As time goes by, the ground around the foundation settles such that the slope of the grade, which was initially correct, reverses and actually runs towards the house directing water towards the foundation. Once this process gets started, it feeds itself as the water leads to further settling and erosion right at the house. This condition seems to actually sneak up on home owners as, despite living in the house for 10 years, they’ve never noticed or thought to correct the condition…until the basement is wet or they sell the house and I show up. I have actually seen houses that have a vertical hole in the ground right under the gutter discharge which goes right down to the foundation weeping tile. Every time it rains, there is a waterfall right beside the foundation. If the basement is not wet, it’s because of a minor miracle.
Another problem that I commonly see in Toronto is the ubiquitous shared driveway which runs between two houses to the rear parking. Usually, the driveway surface butts right up to the side of the house. Because the driveway surface (asphalt, concrete) is relatively non-porous and is sloped to the street, large quantities of gutter discharge water from the back of the house is transported down the surface of driveway trapped between the houses. If the driveway is not shaped with a lowered belly shaped valley in the middle, or swale as it is commonly known, the water runs against the houses resulting in the inevitable basement leak.
Generally, home owners often make a hash of the grading when they install walkways and gardens beside the house. Often the grade is raised too high against the brick or is sloped towards the house. Also gardens installed right beside the foundation are not a great idea because what you end up with is a wet mass of soil right in contact with the foundation for extended periods of time. This dampness can migrate through the foundation wall leading to dampness in the basement.
Grade/Foundation Height
The modern building code requires that the top of the foundation be at least 6” higher then the finished grade. The idea is to prevent snow build-up and surface water from being able to potentially spill over the top of the foundation. I often see homes where either through the installation of a garden beside the house or poor planning on the part of the builder, the finished grade is up on the brick fascia or siding. Brick veneer houses are slight more immune to this condition but with the required weep holes built into the brick veneer, water can find its way through the weep holes into the airspace behind the brick and then drain down over the top of the foundation into the basement.
Roof Water Management
Effective roof water management is imperative to having a dry basement. Again, this is one of those things which is wrong on most of the houses I inspect. A good rule of thumb is to ensure that discharge from roof gutters is at a minimum of 4ft from the house to an area where the grade is such that the water will continue to drain away from the house. Ensure that eves troughs are sloped appropriately and are kept free of debris. Eves troughs which overflow or downspouts which are disconnected, place the roof water directly beside the house. Almost every house I inspect has improper roof water management.
Based on what I have seen in the field, poor grading and roof water management are responsible for 9 out of 10 wet basements.
Foundation Cracks
There really is no such thing as a crack free foundation. Even in the absence of settling of the foundation footing, thin cracks form due to shrinkage during normal concrete curing. These cracks however, which are rarely structural problems, can form the weak points where ground or surface water can enter the basement. Cracks, if of adequate width, can be repaired from inside the basement using a technique where liquid epoxy is injected under high pressure into holes drilled into the crack from the basement. This technique is effective as the liquid epoxy flows into all the nooks and crannies and bonds tightly to the concrete sealing any pathways through the wall.
Another typical crack leak is due to the cross ties used to hold together the foundation form work during construction. These holes remain after the forms are removed, however, they are supposed to be filled with cement. Even so, these can often be a place where a leak can occur as the workmanship of this filling process can be substandard.
Cracks on foundations can also be water proofed from the outside of the house using the techniques outlined in the next section. This can be a better option if the basement is completely finished but it can be a costly retrofit.
Exterior Foundation Water Proofing and Drainage
Older homes were built with no exterior foundation water proofing at all. These homes often have chronically damp basements as the moisture in the soil migrates, unimpeded, into the porous foundation wall and into the inside surface of the basement wall. Early attempts at basement water proofing were done by coating the outside of the basement wall with a bitumous layer (i.e “tar”). This improved the situation but the tar would dry out and crack over time and this solution did not incorporate a drainage layer.
The purpose of foundation drainage is to allow any water which is trapped against the foundation to be transported down to the weeping tile drainage at the foundation footing and away from the house. A foundation which is backfilled with compacted soil may not drain well and water can be trapped against the foundation wall, which allows it to attack any defects in the wall or, in the winter, freezing of this pooled water can cause freeze cracking of the foundation wall due to the pressure applied by the expanding ice. This is a very serious condition where horizontal cracking of the foundation occurs, which can lead to buckling of the wall.
Older homes can have their exterior water proofing upgraded, In my opinion, this is very necessary if you plan on renovating the basement of an older home for liveability. This involves digging a trench all around the house down to the footing, cleaning the wall, applying the layers, replacing the backfill and compacting.
Modern houses include a drainage layer into the foundation design which is comprised of either water permeable back fill (i.e. gravel) or a drainage board right against the foundation. Also, the foundation water proofing has been improved to include a plastic sheet barrier sandwiched between two bitumous layers. The drainage board, if used, is secured on top of the water proofing layers. The use of the drainage board provides mechanical protection between the fill and the foundation water proofing which could be punctured by jagged fill.
Basement Windows/Window Wells
Similar to foundation height above grade, all window sills must be 6” above grade. For basement windows this often requires the installation of a window well. The bottom of the well should be 6” below the window sill. Window wells must have adequate drainage to function. Typically a window well is a large basin were the soil has been dug out and filled with gravel. At the bottom of the basin, a corrugated pipe covered in a filter cloth runs vertically down and connects to the weeping tile. In some houses, the drainage is either inadequate or blocked, which can cause the window well to fill with water to the point where the water spills over the window sill and pours into the basement.
Old Below Grade Drainage
Discharge from roof gutters is sometimes routed into below grade drain pipes as a matter of convenience. These pipes can be connected to the city storm sewer, be routed to a swale on the property, or in older homes, be connected with the house weeping tile. In these older homes the below grade drainage was often made of clay pipes in various stages of failure. If the pipes crack near the house foundation, a large quantity of water can be deposited directly beside the foundation. Typically these older houses have no exterior foundation water proofing so the water often finds its way into the basement.
High Water Table
In some areas, the water table is actually higher then the bottom of the foundation and the house is literally sitting in a pool of water in the ground. These conditions require extensive interior and exterior foundation drainage connected to a sump pit in the basement with a sump pump to push the water up and away from the house. This pump will cycle periodically depending on the amount water being managed by the system.
This type of house placement may be difficult to completely waterproof. However, not all houses with sump pumps have problematically high water tables, they are installed as a precautionary measure. That being said when I see a very active sump pit I take extra care when I survey for moisture issues especially in houses with finished basements. I also am sure to warn my clients about the penalty of a potential sump pump failure -> i.e. a flooded basement. I recommend that a system with both mechanical and electrical backups be installed to protect against flooding in the event of a power or pump failure.
What should your home inspector tell you?
Any inspector should warn prospective buyers about the implications of incorrect grading, roof water management, foundation height, window wells and below grade drainage even if there are no signs of water ingression in the basement. Foundation cracks should be assessed for signs of leaks and recommendations made to the client as to potential remedies.
Finally, since a home inspector can not predict if a basement will remain dry under all rain, wind and snow conditions with a certainty, it is best to be proactive with any issues identified by the inspector and implement the changes before they become costly problems.