Structure - Midterm Flashcards
You are required to probe structural elements where deterioration is suspect. When would probing not be required?
- Where it would damage any finished surface
- where no deterioration is visible
Under what conditions are you not required to inspect crawlspaces?
- dangerous to you or other people
- will damage the property
- not readily accessible
Under what conditions would you not enter the attic
- dangerous to you or others
- it may damage the property
- not accessible
- health hazard (animal feces)
T or F
Most standards require you to explain how you inspected the crawlspace or an attic
True
T or F
Most standards require you to inspect a foundation footing
False
What is the function of a footing?
Transfer the live and dead loads of the building to the soil over a large enough area so that neither the soil nor the building will move
What is the function of a foundation?
- Transfer loads from the building to the footings.
- Act as retaining walls, resisting lateral soil pressure
3 common foundation configurations
- Basement
- Crawlspace
- Slab-on-grade
7 common footing types
- Spread/Strip
- Pilasters
- Pad
- Piles
- Piers
- Grade beams
- Caissons
Examples of Live Loads
weight of people, furniture, snow, rain and wind
Examples of Dead Loads
- The weight of the building materials
- The soil surrounding the foundations
What is the difference between a strip footing and a pad footing and where would each be used?
- Strip footing or spread footing is used under a foundation wall
- A pad footing is used under a column
-Pad footings distribute concentrated loads. Strip footings handle more evenly distributed loads.
7 Foundation materials
- Concrete
- Concrete block
- Cinder block
- Brick
- Clay tile
- Stone
- Wood
T or F
As long as the footing is below the frost line, it is not a problem to let the temperature in the basement go below freezing
False
What is the difference between a pilaster and a pier?
Pilaster - a thickening of a foundation wall to accommodate the concentrated load of a beam resting
Pier - a stand-alone structural member that can be thought of as a column sunk into the ground.
Typical materials for piles?
Shapes and dimensions?
Concrete, steel or wood
Circular - 8” to 14” diameter
Square - 6x6” to 12x12”
T or F
When a foundation is supported on piles, the piles are typically visible for inspection
False
List 7 soil types from strongest to weakest
- Bedrock
- Gravel
- Coarse Sand
- Fine Sand
- Clay
- Silt
- Organic material (Weak - not suitable for building)
T of F
As long as we keep the inside of the building heated, frost can’t get down under the basement floor
True
T or F
Footings and foundations should be strong so they can transfer loads and durable with respect to exposure from air, water, soil and insect attack
True
4 causes of cracks in foundation walls.
- Shrinkage
- Settlement
- Heaving
- Horizontal Force
Explain the difference between uniform settlement and differential settlement.
Uniform settlement - the settlement is uniform, the entire house moves and no cracking develops
Differential settlement - one part of the house moves relative to another, which results in cracking
What is a shrinkage crack and what causes it?
Cracks that commonly occur on the concrete foundation wall, typically within the first year after concrete is poured
Caused by natural curing of concrete
Characteristic of shrinkage cracks
- Relatively small - less than 1/8” in width
- Vertical or diagonal.
- Do not extend to footings or structure above
- Do not have corresponding cracks elsewhere in the building
- Usually occurs at stress concentration point in the wall.
- Radiates down from corners of basement windows
What is the main implication of a shrinkage crack?
Leakage
There is no structural implication
Typical causes of differential settlement
- Footing - missing, small, deteriorated
- Soil under footing - disturbed, weak, expansive, eroding, freezing and heaving
- Load increased - snow and ice, building additions
T or F
When there is a crack, It’s possible to determine the rate of movement at the time of the inspection?
False
What is a cut and fill lot?
Implication on building settlement
A side-hill lot where some of the hill is cut away to allow part of the house to fit into the hillside. The excavated material is often used to fill in the lower part of the slope and create a level pad for the rest of the home. Part of the house sits in the cut area and part of the home sits on the filled area.
The filled area is disturbed soil and is more likely to settle.
It is a good idea to inspect the neighborhood as you are arriving at an inspection. What kinds of things should you look for and how can they help you in your inspection.
- Structural problems in other houses - Topography (e.g. flat or slope)
- Age of the neighborhood
- Soil condition research
Which crack would be more serious? A crack that has moved in one plane or a crack that has moved in two different planes.
A crack that has moved in two different planes
Clues that indicate the crack may be active
- Opened patches - active
- Cracks with no paint in the cracks - may not be recent crack
- A lack of dirt and debris in the crack - old crack
- Sharp corners on cracks - old crack
What is underpinning and in what situation would it be used?
Re-supporting footings from below.
Used to stop differential settlement - the soil below the building should be able to support the underpinning
4 Types of Settlement cracks
- Uniform
- Severe uniform
- Differential
- Tipping
Implications of settlement cracks
- none if cracks are not present
- cosmetic
- leakage
- sloped or uneven floors
- broken utility lines
- leaks in roof due to chimney flashing and pipes movement
- unstable chimneys
- floor, ceiling joists and rafters losing their end bearing; potential floor or roof collapse
- collapse of floor, walls and roof
What is the maximum slope for a lot should be?
1 in 2
(for every two feet of horizontal distance along the surface, the ground should not rise or fall by more than one foot)
T of F
Differential settlement cracks usually have more than one
True
T of F
Differential settlement cracks are restricted to the foundation
False
They can extend down through the footings and up through the structure
7 possible corrective actions against differential settlement
- Mud jacking
- Underpinning (helical anchors)
- Adding piles
- Foundation irrigation systems
- Remove and replace footings or foundations
- Steel rods, cables, or channels
- Demolition
How deep should the bottom of footings be?
A minimum of 12” below undisturbed soil or the frostline, whichever is deeper
How far apart should the steps be on step footings?
At least 2 feet (24”)
Where would a step footing be used and where would you look to find cracks?
Houses built on sloped lots
Vertical, Diagonal, Horizontal cracks at each step
Clues to lowered basement
- Curbs around the perimeter indicating bench footings
- The foundation wall material changes part way down, indicating underpinning
- Unusually high basement ceilings
- New or extended basement stairs
- Furnaces or other equipment on raised pads on the floor
- Utility lines entering or leaving the house above basement floor level
- Sump pumps or sewage ejector pumps
- Interior foundation drains
- The basement floor is different from other houses in the area
What problems could result from lowering a basement floor?
- May undermine the original footings.
- The original footing may settle down onto the new foundation and footing system that shrinks while it cures.
- Flooding and leakage problems
Why would a settlement crack develop at the joint between old house and an addition?
Because the original house has settled before the addition is added.
As the addition settles, it moves relative to the original house, resulting in a crack.
What is a concentrated load?
A large load sitting on a small concentrated area
(e.g. end of a beam, bottom of a chimney or a column)
4 Common causes of Heaving cracks
- Frost heaving
- Adfreezing
- Expansive soils
- Hydrostatic pressure
Which part of the house does Adfreezing acts directly on?
- Footing
- Bottom of the foundation
- Sides of the foundation
The sides of the foundation
4 Causes of frost heaving
- Saturated soils
- House left unheated during winter
- Basement walls insulated, causing greater frost depth around the house
- Too shallow footings
T or F
Frost heaving will only exert force in vertical direction
False
T or F
There must be moisture in the soil to have frost heaving
True
Even if footings are too shallow, no heaving cracks will develop unless there is moisture in the soil
2 Corrective actions on the exterior of the house against frost heaving
- Remove soil moisture
- Protect the footings against freezing
(e.g. uninsulate basement walls, raising the grade, insulate ground around the house)
T or F
It is not possible for a high water table to cause heaving because the drainage tile around the house will handle the water
False
T or F
Horizontal cracks are rarely a structural problem
False