INDICATORS OF PROBLEMS
COMMON PROBLEM CATEGORIES
STRESS FEATURES AND OTHER CONDITIONS
The most common indicators of problems are stress features and other conditions like cracks and separations, floor slope, wall tilt, soil features, seepage, poor drainage, and landscape conditions. These conditions may be observable singularly or in combination and at varying degrees.
- Q: What are the most common indicators of soil related problems?
- A: The most common indicators of problems may be observable singularly or in combination and at varying degrees (stress features) are:
- Cracks and separations
- Floor slope
- Wall tilt
- Soil features
- Poor drainage
- Landscape conditions
Cracks and Separations
Cracks are usually the first stress feature noticed which would suggest a problem. The terminology "stress feature" is utilized because it is a simple, objective description of a feature resulting from stress induced.
- Q: Where are cracks and separations usually located and why?
- A: Cracking is typically noticed within the structures brittle surfaces such as plaster, stucco, masonry, and concrete. Cracks are usually the first stress feature noticed which would suggest a problem.
- Q: Why do I see cracks in my walls but not my slab?
- A: Cracks resulting from soil influences may first appear in wall and ceiling surfaces, while floor slabs and foundation cracks are detected later since the slab and foundation system are usually substantially concealed by flooring and other finishes.
Floor Slope and Related Features
Possibly the most common category of structure deformation is floor slope. Frequently cracks will begin developing in slabs when floor tip approaches the one-inch in twenty feet ratio (ratio of about one inch vertical over a 20 foot horizontal distance).
- Q: What are common features of floor slope?
- A: Other features commonly associated with floor deformation are:
- Stuck doors
- Differential gaps between doors and doorjambs
- Misalignment of sliding windows and doors
Wall tilt frequently goes undetected, but can be a useful clue in assessing site soil and structure behavior.
- Q: Why is my wall tilting?
- A: Most freestanding walls (retaining) are expected to tilt slightly in response to soil pressure behind the wall and correspondingly from the ordinary bending of the wall itself in response to the pressures imposed.
- Q: Can tree roots cause wall tilt?
- A: The extent to which tree roots influence wall tilt will vary with many factors including:
- Depths and distances to which tree roots extend
- The characteristics of individual tree species
- Soil and bedrock conditions
- Non-environmental factors
Nonetheless, for trees to be of significant influence they usually have to be fairly close to the top of retaining walls.
- Q: Was the floor built out-of-level, or has there been a uniform tip of the structure overall?
- A: If the house was built out-of-level, the walls would be expected to be essentially vertical. For buildings that have rotated, walls may be correspondingly tilted. When floor tilt occurs, it is also not uncommon to have structures adjoining to the main dwelling separating in response to the differential movement.
Soil and Salt Observations
Direct soil observations can be useful indicators of problems or potential problems.
- Q: Why do you need to test the soil?
- A: Simple observations of soil conditions where exposed and other surface features can provide powerful clues into potential soil and structure behavior.
- Q: What if the soil is covered?
- A: Where an area is covered with asphalt or continuous sections of concrete, soil settlement inducing compressive stresses can sometimes be detected by distinct bulges, which develop in streets (i.e., much like speed bumps).
- Q: What if I have clay soil?
- A: Clay soil tends to be considerably more problematic than sand. Surface exposures of clay should alert the reviewer to the possibility of potential problems with clay soil. A random crack pattern in the clay soil is indicative of expansive behavior.
- Q: Why do I have corrosive soil?
- A: Corrosive soil is usually the result of relatively high concentrations of certain soluble mineral constituents within soil.
- Q: How do I know if salts are present?
- A: Salts can in some cases be seen on the surface of soil in the form of white powdery crystallizing evaporates which form on the surface as the soil moisture evaporates (often referred to as efflorescence). It is not uncommon to see examples of salts at toe-of-slope areas down which soil moisture migrates resulting in higher soil moisture below the surface and, as such, greater surface evaporation.
- Q: How do I identify salts on my structure?
- A: Salt lines (evaporative fronts) are also common to foundation stems. The identifiable line will commonly occur a few to several inches above the soil grade line from which the salts are migrating. Where cracks occur in foundations, the salt lines may vary on each side of the crack depending on how soil moisture and other factors vary.
- Q: What can you determine from the presence of salt?
- A: In the case of open foundation cracks, the presence or absence of salts within the cracks can provide useful clues as to the relative age or causation of the cracks. Similarly, salts may develop in a patchy fashion on the face of a retaining wall. Such observations are likely to suggest moisture migration directly through the slab or wall.
Moisture and Drainage
Seepage and drainage problems are usually intuitively obvious.
- Q: How can I tell if I have a moisture related problem?
- A: Direct wetness, dampness, mold and mildew, efflorescence (surface accumulation of mineral salts) and staining are frequent indications of a moisture problem.
- Q: What causes interior moisture problems?
- A: Surface and/or subsurface soil and bedrock gradients directed towards the building as opposed to away may contribute to interior moisture problems. Of course, ponding adjacent to a building might contribute to potential moisture problems on the interior.
- Subtle color differences
- Minor stucco spalling
- Concrete surface pitting
Moisture-related problems may be indicated by:
- Q: Where can I look for these indicators?
- A: The indicators may not always be directly apparent. It may be necessary to lift the corners of carpet to expose indicators. Similarly, it may be necessary to move a few stored items from the floor of a garage to examine the differences on a covered surface versus an exposed surface. Since indicators like efflorescence are easily swept away or washed away, it is frequently necessary to look beyond open areas exposed to high traffic.
Roots can adversely interact with structure performance. In a sloping environment, tree growth can be a useful indicator of slope performance.
- Q: How can landscaping effect my structure?
- A: Medium and large trees close to buildings are frequently potential problems. Roots can adversely interact with structure performance.
- Q: How far away should a tree be placed?
- A: Medium trees should not be closer than about ten feet from the building. Even at this distance, root trimming and/or root barrier might be required over the years. Larger trees should be kept at an even greater distance. Significant root systems can extend well beyond the drip line of a tree. As a rule of thumb, tree roots can be estimated to extend out from a tree at a distance equivalent to the tree height.
- Q: How can trees indicate slope failure?
- A: In a sloping environment, tree growth can be a useful indicator of slope performance. Curved tree trunks are a common indication of creep. Where the condition of tree trunk curvature is acute, this could be an indication of particularly weak soil, relatively high rate of creep, and accordingly, risk of greater instability.
Changes in the performance of vegetation can also be an indicator of actual or potential problems.
Even though some indicators or problems are so obvious that conclusions can be readily drawn, more often the reviewing professional is faced with subtle indicators, which require more detailed assessment. Of primary importance are the qualifications of the reviewer. Of secondary concern is magnitude. The reviewer should first determine the pattern of stress features followed by review of the magnitudes. With an understanding of the implications of patterns and magnitude, the reviewer can then make a reasonable assessment of whether the stress features are indicative of a particular problem.
Separations in appurtenant flatwork are usually widest near the slope. Understanding the significance of magnitude and variations in magnitude can play an important role in assessing adverse influences.
- Q: How do I know if a stress feature in my wall is insignificant?
- A: Ceramic tile cracks are usually objectionable at any width. Plaster wallboard cracking at greater than 1/64 inch is usually sufficient to dictate at least cosmetic treatment. Under wallpapered surfaces, cracking might extend to as much as 1/16 inch before becoming noticeable unless tearing of the wallpaper occurs first.
- Q: How do I know if a crack in my slab is insignificant?
- A: In absence of other considerations, isolated foundation cracks in typical slab-on-grade construction up to about 1/16 inch are not generally alarming. In typically older, raised-wood floor homes, foundation cracks up to about 1/8 inch are common and, in many cases, would not likely be contributing to any functional impairment. Concrete separations at control joints in exterior flatwork up to about 1/4 inch are frequently deemed insignificant provided there is no appreciable vertical differential or other significant adverse implication.
When the strength of individual material elements is exceeded, the stresses cause cracking and related movements. By examining the pattern of stress features the character of deformations contributing to those stress features can be best identified.
- Q: What information can you derive from stress features?
- A: Once an understanding of the structure deformation exists, a basis is established for suggesting the likely cause or causes of the problems. Nonetheless, it is common for significantly adverse geotechnical influence to produce a stress feature, which appears in initial review to be consistent with ordinary structural adjustment.
- Q: Why am I noticing problems on the opposite side of the room from the original stress feature?
- A: Commonly, but depending on magnitude, if the described condition occurs on an exterior wall, the stress induced may produce interior wall features such as a stuck door on a parallel wall.
- Q: Why does settlement occur?
- A: Compression or settlement occurs as stress is imposed on soil and/or there is a reduction in the soil's capacity to support loads.
- Q: Where is settlement of most concern?
- A:Settlement is usually of most concern in fill areas although natural topsoil and certain unconsolidated sediments may also be prone to settlement. The most significant stresses on fill usually result from the weight of the fill itself, but some stress is also induced by the weight of the structures above.
- Q: Can water effect settlement?
- A: Settlement can be aggravated by the introduction of water into the soil. Thus, depending on the initial load, dry density and moisture content, a clayey fill soil could either expand or settle with the introduction of moisture.
- Q: What are some of the causes for settlement?
- A: Settlement failures of fills have been attributed to by a number of causes. These include placing fill:
- On natural slopes from which the existing vegetation and compressible topsoil materials have not been adequately removed
- In layers that are too thick to be adequately compacted
- Incorporating large quantities of gravel, cobble, and boulder material which impede the compaction effort
- Simply with inadequate compaction energy and/or at moisture contents which are incompatible with proper compaction
- Q: What causes expansive soil problems?
- A: Expansive soil heaves when water is introduced and shrinks when it dries. Pressures induced by heaving soil can be large enough to lift most buildings.
- Q: What are the common indicators of expansive soils?
- A: This process generally tends to:
- Increase separation of slab joints and/or cause exterior improvements such as patios and other originally abutting structures to separate
- Create cracking in slabs, foundations and stucco
- Lift outer edges of building
- Cause a range of damage from nuisance level to total structural loss.
- Q: What influence does expansive soils have?
- A: The action of expansive soil can directly influence foundations and slabs as well as earth pressures imposed on retaining structures. Expansive soil action can also significantly aggravate the tendency for slopes to yield and the tendency for surficial slope instability to develop.
- Q: Where does the water come from?
- A: Expansive soil related problems in areas of inadequate foundations can be aggravated by poor drainage and landscaping. Poor drainage facilitates the introduction of water into the expansive soil. Sometimes, heavy irrigation necessary to maintain certain plant varieties can also result in heave of adjacent slabs. It is common upon review of an older home in an expansive soil environment to find that the lowest point in the house corresponds to the corner of the house nearest the front or rear yard tree. Temperature differences also tend to drive moisture toward the cooler area under the slab.
Most landslides can be divided into two categories based upon the shape of the main failure surface. A rotational slide is one in which the failure plane is broadly arcuate with a spoon-shape failure surface generally concave upward. A transitional landslide is one, which occurs along the weak planer or thinly laminated surface. Complex slides which incorporate both rotational and translational components are also common.
- Q: What is a translational slide?
- A: Many landslides in urbanized areas are related to man’s activities in various degrees. When the slope is cut for grading, support may be removed from the bedding surfaces and translational failure may result. It is not uncommon for translational slides to occur rather rapidly, tearing apart homes and displacing streets. Translational landslides may progress over great lengths of time, particularly where little or no support is added to the toe as movement progresses.
- Q: What is a rotational slide?
- A: In contrast to translational failures, rotational landslides tend to become more stable as movement progresses. As failure occurs, the mass rotates backwards. Usually the movement slows/stabilizes when the landslide debris dozes out onto the adjacent flat pad or when the debris builds up against an opposite canyon wall.
- Q: What influences landslides?
- A: The most landslide prone rocks are typically composed of predominantly fine-grained materials such as siltstone and shale. Factors besides rock type which influence massive landsliding are:
- The steepness of the slope
- The internal structure or fabric of the soil or rock units involved
- The rate of erosion near the base of a slope
- Above normal rainfall
- Earthquake occurrence
- Expansive soils
- Water line leaks
- The works of man
- Q: How do you recognize landsliding?
- A: Techniques include:
- Subsurface investigation
- Aerial photographic reconnaissance
- Field mapping
Landslide characteristics may be obscured by modification of the terrain, vegetation, and construction making detection difficult.
- Q: What triggers a landslide?
- A: Moisture is commonly a very important factor in landsliding. This relationship is evident by observing that most landslide activity occurs during or shortly following a rainy season. Moisture can contribute to instability in the following ways:
- Rainfall erodes the base of slopes, thereby removing support
- Absorbed water also increases the weight of the soil and rock mass
- More importantly, increasing moisture can decrease the effective strength of the soil and rock mass by softening and increasing pore water pressure between soil and rock particles.
- Water also directly influences the material character of a clay soil by providing a hydrating or lubricating effect, which reduces friction
- Q: What causes landslides?
- A: Although water absorption may trigger a landslide, the water is frequently not the basic cause, which creates the unstable ground condition. More frequently, the underlying cause is the adverse soil or geologic condition. Also, original design or construction defects can be causes.
The surficial slump is the most common form of landsliding. This is a form of slope instability in which a zone of soil, generally parallel to the slope face, slides down the slope.
- Q: How do landslides commonly take form?
- A: The failure area generally takes the form of an oval, and the depth of the effected zone is usually less than about four feet, but occurrences to six feet and greater are not uncommon. The slump debris generally winds up a few feet below its original location, leaving a near vertical escarpment above and bulged toe area.
- Q: Can vegetation help prevent a landslide?
- A: Logically, a slope with well established deep rooting vegetation might be improved by the soil reinforcing aspect of the root systems. Frequently, slopes with apparently well established vegetation fail. Examination of the failure areas indicate a concentration of surface roots and little or no roots below about three to four feet.
In most cases, erosion potential does not result in high risk of damage to improvements. Nonetheless, an erosion area left unattended can deteriorate and be very costly to remediate. In many cases, erosion that results in silting across sidewalks, slip-and-fall hazards are created. The conditions which control erosion are highly variable in origin, rate, and capacity to cause economic loss.
- Q: What causes erosion?
- A: In general, erosion is caused by the movement of water, ice, and wind. Usually rainfall, related stream-flow and ocean wave activity are the most effective erosional agents.
The process of creep involves very slow movement, on the order of inches per year or less. Because of the slow rate of movement, commonly no distinct separation or failure is observable in the ground surface. Nonetheless, the slope process can result in substantial tilting and cracking of structures above effected slopes. Compacted fill slopes, particularly those composed of expansive clayey soil, are also often significantly impacted by creep.
- Q: How do you detect slope creep?
- A: Creep may be difficult to detect, particularly over a short period of time.
Deformation resulting from long-term, slow-rate creep can have a serious effect upon roadways, drainage structures, fence lines, screen walls, retaining walls, utilities, homes, and other improvements. Indicators that creep may be active on a site include:
- Tilting and separation of walls in a down slope direction
- Tension cracks near the top of a slope
- Curved trunks of trees, which have been growing on a creeping slope for many years
- Q: What are the common forms of slope creep?
- A: Creep will typically occur in about four common forms, frequently in combination. The most common form of creep is the seasonal expansive soil creep process. This process might be expected to influence the outermost ten to twenty feet of a slope.
Another creep process is slope softening. The slope softening process occurs without significant volume change and without necessarily involving massive or surficial failure. Slope softening tends to be of most concern in compacted fill areas. After construction, when additional moisture is introduced into the fill through irrigation, rainfall, groundwater, and/or other sources, the fill mass increases in weight. As this lowering of strength occurs, strain must also occur in order to mobilize the needed additional strength to maintain stability.
Creep can also occur without changes in moisture described in the foregoing paragraphs. In slopes of sufficient height and steepness, weak clay soil at constant moisture, usually at or near saturation, can be prone to movement analogous to the flow of a viscous fluid. This process is alternatively described as creep at constant moisture, creep at constant suction, creep at constant stress, or simply classic creep. Creep can, therefore, be a relatively slow, steady, downhill process or a more cyclic process influenced by seasonal changes.
In new construction, slope creep and the effects of slope creep can be controlled somewhat by designing lower, flatter slopes and by taking special care in the design and construction of improvements behind descending slopes.
Soil with a high percentage of certain chemical constituents when brought in contact with certain structural elements can cause corrosion. Whereas sulfates tend to be corrosive to the cement paste, chlorides contribute to corrosion of the embedded steel.
Sulfates and Chlorides
Soluble sulfates in sufficient soil or water concentrations can be significantly corrosive to concrete, but high concentrations of other mineral salts are also of concern. Even at a relatively low-level concentration, sulfates and other mineral salts within the soil can produce problems.
- Q: What if my soil contains sulfates?
- A: Contact with soil of high soluble salt content can cause corrosion of foundations and slabs. The most aggressive substances, which disintegrate concrete, are sulfates of sodium, magnesium, and calcium, which are commonly referred to as white alkali.
- Q: What can sulfates do to concrete?
- A: Sulfates react chemically with hydrated cement components causing leaching of cement constituents and/or expansion and disruption of the paste. Deterioration of the concrete is the result. The best protection against sulfate related damage is good quality concrete.
- Q: Can this effect cracks in my slab/wall?
- A: Along concrete cracks, salts tend to precipitate in very high concentrations as moisture from the soil below evaporates through the cracks. This can leave heavy salt deposits on the concrete surface, which can cause further deterioration of ordinary concrete. Concrete block masonry frequently falls victim to corrosive salts. Particularly when walls lack proper waterproofing, the concentration of salts in efflorescence can corrode the block surface destroying the outer block face for which the compressive strength is essential to structural integrity.
- Q: What will salts do to the exterior of my structure?
- A: On the exterior of structures, soluble salts can cause spalling of stucco surfaces. Build-up of efflorescence and stucco spalling are the most common indicators of corrosive soil. Even in the absence of sufficient concentrations to deteriorate concrete, mineral salts can build up behind the finished coat of stucco on structural walls and push off the painted and/or stucco surface.
- Q: Why does mineral salt deposition occur?
- A: Mineral salt deposition occurs as the result of salt crystallization, which develops as moisture evaporates. The process is not unusual on older homes and is ordinarily dealt with by periodic cosmetic treatment provided concrete deterioration is not suspected.
- Q: What if my soil contains chloride?
- A: While chloride and other salts are relatively harmless to hardened concrete, they will contribute to the corrosion of aluminum door and window framing as well as embedded steel. The corrosive effect of these and other mineral salts can be indirect. When high concentrations of mineral are present in a moist soil, the soil will possess relatively high electrical conductivity. This allows minute currents to develop, which, in turn, cause galvanic corrosion.
- Q: How do I repair the damage?
- A: In areas of high mineral salt concentration, buried pipes and other susceptible metal surfaces require special protective coatings and/or other construction techniques to mitigate deterioration. After construction, relatively fewer options exist for treatment. Most positive approaches involve partial to total replacement of slab and foundation systems. Foundations can be encased in resistant concrete.
Although seismic activity is of interest in several areas of the country, the western United States, particularly the west coast, are generally thought to have the greatest seismic concerns.
- Q: What are the effects of earthquakes?
- A: There are three principal effects of earthquakes, which can be categorized as shaking, surface rupture, and liquefaction. While very large areas can be affected by shaking, a much smaller area may be affected by surface rupture. Earthquake shaking is largely due to the release of seismic energy during periods of sudden displacement along the faults.
There are three (3) basic types of faults. A normal fault is one in which extension of the terrain has caused the hanging wall to drop with respect to the footwall. In a reverse fault, also known as a thrust fault, compressional forces cause the hanging wall to move up with respect to the footwall. Finally, in a lateral or strike-slip fault, rocks on either side of the fault move laterally past each other.
- Q: How do you measure building performance?
- A: Some believe a more useful scale for the measurement of building performance is an intensity scale. It is difficult to compare magnitude and intensity because intensity is linked with the particular ground and structural conditions of a given area as well as the distance from the earthquake epicenter. In contrast, magnitude depends on the actual energy released by the earthquake.
- Q: How do you predict seismic risk?
- A: Predicting seismic risk in a given area is difficult because there are many parameters, which are not clearly known or understood. The extent of damage produced from a given earthquake is dependent upon many factors including:
- Distance from the epicenter
- Characteristics of the rock or soil
- Depth of the earthquake
- Location with respect to the active fault branch
- Magnitude of the earthquake
- Duration of ground shaking.
- Q: Can structural design effect my structure?
- A: Older construction tends to be more prone to earthquake damage than more recent construction incorporating seismic design. Experience has demonstrated clearly that structural collapse resulting from earthquakes generally occurs in older structures without seismic design.
- Q: If I have a new home, will it be ok?
- A: For more recent construction lacking construction defects, collapse is infrequent, but serious damage can occur which may result in demolition of the building at a later date.
- Q: How does construction defects affect my structure during an earthquake?
- A: January 1994 Northridge earthquake, it was determined that where partial or complete structural collapse occurred, construction defects played a significant role. In sorting out earthquake damage from other damage, it is important to look for patterns of damage. Patterns should be consistent with the orientation of the principal ground motion. Damage patterns may also be independent of patterns expected from other soil phenomena. Earthquakes can also simply serve to worsen damage caused by other problems.
Landslides, Ground Rupture and Liquefaction
When direct earth-related damage occurs, it usually takes the form of ground rupture and liquefaction.
- Q: How do earthquakes trigger landslides?
- A: Earthquakes can cause landsliding by initially damaging pipelines and drain lines, which, in their damaged condition, served to introduce water and thereby destabilize the hillside. Ground rupture is the tearing of the ground surface corresponding to the fault movement.
Frequently, areas of liquefaction risk are associated with coastal areas with high groundwater and usually fairly loose natural or filled sandy soil.
- Q: Is it possible that the stress features I see are normal?
- A: In many cases, certain ordinary structural considerations exist which serve to suggest a soil problem or otherwise complicate structure conditions making assessment of overall problems more difficult. As such, the following sections describe various ordinary structural conditions commonly co-existing with features, which are of a soil or geologic nature. Understanding these common construction materials and their structural considerations is an essential aid to sorting out soil and geologic influence.
Shrinkage is a normal process which occurs in most cement and plaster materials. Concrete, stucco, and masonry are most commonly affected. Shrinkage generally occurs during the original curing and is a function of the original water content.
- Q: Where do shrinkage cracks form?
- A: Shrinkage cracks generally develop at the corners of windows and door openings where stress concentrations occur and in other predictable locations such as across the central portion of long continuous areas such as walkways and strips of stucco walls. Continuous masonry walls without control joints are also prone to near vertical shrinkage cracking.
- Q: Is there any way to prevent shrinkage cracks?
- A: It is often attempted to limit and/or distribute shrinkage cracking in slab areas by providing steel reinforcement. Control joints are also used to control locations of shrinkage cracking but control joints are seldom used in slabs within residence interiors. Where joints have been attempted on interiors, they have been associated with disruption of the floor finish (i.e., cracked tile), moisture intrusion, and insect infestations.
Temperature stresses produced by heating and cooling can also produce cracking similar in pattern to shrinkage cracking. With respect to plaster and stucco, it should be recognized that although actual volume changes resulting from temperature differences tend to be very small. Some level of shrinkage cracking can be found in most homes.
Warpage is also of concern as moisture changes occur in lumber.
- Q: What does warping mean to a structure?
- A: As lumber dries, splitting results from uneven shrinkage. The twisting can occur over several degrees. The result of the twisting is commonly a fine crack extending below the beam seat. Excessive warpage is commonly an indication of either green lumber being utilized on a project, or possibly the lumber absorbed water through rainfall or other sources prior to completion of construction.
In addition to warpage, moisture changes in wood can result in significant volume changes. Volume changes with the degree of moisture change and differs with lumber species.
- Q: What other structural stress features should I be aware of?
- A: In addition to shrinkage and other phenomena described above, seating, sagging, settling, and shearing are also processes contributing to structural adjustment which, in turn, can result in various stress features apparent in construction.
Seating can occur at the junction of wood elements. Another common form of a structural adjustment is simply sag in wood floors and ceiling systems. Roofs are also prone to sagging, particularly when heavy cement tile or ceramic roofing materials are utilized. In effect, green lumber becomes smaller as the wood dries.
- Q: How much settlement can I expect?
- A: On any project some settling of foundation is considered ordinary. Any material is going to compress when loads are applied. This is true for soil. It is also true for steel and concrete. Usually total soil movement should be less than about 3/4 to one inch.
Differential movement between adjacent foundations is usually expected to be less than about 1/4 inch. Floor tip in response to soil movement should be less than one inch vertical over a 20-foot horizontal distance to avoid normal detection.
- Q: What stresses can occur?
- A: Corresponding to these movements’ shearing stresses can be induced. Shear stresses, in essence, represent the tearing effect induced by loads and stress conditions. Shear cracking can be apparent by the crack pattern, which can consist of a series of sub-parallel diagonal cracks. Understanding the structural make-up of a building is important to assessing the various types of ordinary adjustments that might occur.
Tolerances can actually be considered in three general areas. These areas are with respect to design, construction, and performance expectations. Structures must conform to proper designs. The designs must conform to use criteria as well as structural and other system criteria which are the subject of architectural analyses, engineering analyses and code regulations. Construction tolerances represent how precisely designs are implemented and as such are a matter of craftsmanship.
- Q: How can I determine if there is an unreasonable defect?
- A: User expectation is the ultimate tolerance category. Regardless of the specific design and construction criteria, the structure must perform in a manner consistent with the reasonable expectation of the user for which the building is designed and constructed. Thus, even if a structure is properly constructed and conforms to normal settlements and other ordinary adjustments, the structure can be considered to have failed if performance does not conform to the reasonable expectation of the anticipated user.
- Q: What is considered a unreasonable defect?
- A: Simple examples include stuck doors, perceivable floor tilt, and even hairline floor tile cracks which may have occurred as a result of the reflection of otherwise normal, fine slab cracking below the tile. Dampness, mold, and mildew problems are other common examples of failure to meet the reasonable expectation of the user. Common sense is a good guide to identifying user expectation defects.
Drainage and Moisture Problems
- Q: What can insufficient drainage and presence of moisture introduce?
- A: Occasionally, moisture problems can contribute to significant structural damage and/or costly repairs. Drainage and moisture problems can affect homes in both hillsides and flatland areas. Drainage and moisture problems occur in various soil types ranging from relatively clean sands to clay.
- Q: How can drainage affect a hillside?
- A: Drainage problems in hillside areas can result from uncontrolled sheet flow to run-off from the hillsides. Concentrated and otherwise uncontrolled flow can also be a substantial problem. For most construction in recent years, some consideration is given to addressing the run-off of natural hillsides. Usually collecting swales and storm drain systems are provided. In manufactured slope areas, typically brow ditches, terrace drains, and toe swales are provided to collect and direct run-off to suitable disposal areas.
- Q: What if I had ponding?
- A: The most common category of moisture problem is exterior ponding producing adverse effects such as unsightly conditions, landscape impairment, algae, an insect brooding environment, and/or occasionally hazardous, slip-and-fall conditions.
- Q: What if water is migrating into my structure?
- A: Significant problems can also result from moisture migrating into basements, garages, and home interiors. Inadequate retaining wall waterproofing is the common culprit for below grade problems. Above grade penetrations usually result from roof leaks and flashing problems around window and door openings. The problems are usually manifested in the form of wetness, dampness, discoloration, mold and mildew, efflorescence, plaster and stucco spalling, and paint peeling.
- Q: Why is water migrating through the concrete?
- A: The process of migration through concrete, sometimes referred to as wicking, will occur most often at the perimeter of a building and is usually associated with poor quality concrete. Wet soil, poor drainage, and/or a retaining wall forming the edge of an interior space will tend to aggravate interior moisture intrusion problems.
- Q: What if I can’t find water but have signs of moisture?
- A: Moisture problems can occur without particular deficiencies in walls, floors, or retaining walls. In coastal environments, high ambient moisture combined with poor air circulation can result in green fuzzy shoes at the rear of closets, clothes and walls spotted with mold, discolored carpet, mildew odor, general dampness, and may lead to health problems.
- Q: How can I resolve this?
- A: Where specific estimates of moisture intrusion are desired, simple testing can be conducted. This type of test is sometimes conducted prior to the installation of vinyl flooring or carpet on concrete.
- Q: How can landscaping affect me?
- A: Landscaping can interact with foundations directly or indirectly. Various problems can result. Tree roots can lift foundations and slabs as well as apply pressures to retaining walls which exceed design values. In expansive soil moisture, extraction via root systems can result in significant soil shrinkage and resulting structure subsidence.
Care should be taken in designing a landscape scheme, irrigation and maintenance practices. Drainage gradients should be increased in relation to the soil conditions and the landscape environment.
- Q: What is a Geotechnical Soils Report?
- A: A Geotechnical Soils Report is a report generated by a registered professional Geotechnical Engineer, which assesses the geologic soil condition in the subject area. The information provided in the report offers scope or work and design parameters to be used to ensure stability of the proposed structure.
- Q: Why do I need a Geotechnical Soils Report?
- A: In order to obtain a building permit, you must submit a Geotechnical soils report to the city of which the proposed structure is to be built. The building permit is issued if the city feels that the existing property meets the current standards. This information is drawn from the Geotechnical Soils Report.
- Q: When do I need to provide a Geotechnical Soils Report?
- A: The report should accompany a development application for development. Construction should never begin without this report.