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
6 Things that could cause horizontal force on a foundation
- Frost pressure
- Hydrostatic pressure (wet soil)
- Vehicle loads adjacent to the building
- Expansive soils
- Tree roots
- Impact damage (careless backfilling)
T or F
A bow or a bulge in a concrete foundation wall is a result of forces that are applied over a very long period of time
True
Why might the horizontal crack disappear near the edge of the wall?
The perpendicular wall reinforces the cracked wall near the end, preventing it from moving
What is a lateral support for foundations?
A floor system secured to the top of a foundation wall, preventing it from tipping inward.
What might cause a damaged foundation wall to start moving after heavy rain?
Increase in hydrostatic pressure, or swelling of expansive soils.
6 Corrective actions to cracks, bowing, bulging or leaning of the foundation wall due to lateral forces
- Buttresses
- Pilasters
- Wood or Steel beams
- Helical anchors
- Sister walls (int or ext)
- Removal of water from the soil
What is a buttress?
What is a pilaster?
A buttress is a large structural mass placed against a wall to resist horizontal movement. It can be above or below grade
A pilaster is a vertical thickening of the wall. It may act as a reinforcing beam for the foundation wall and is often designed to carry concentrated vertical loads
2 causes of mortar deterioration in foundations
- Poor quality mortar
- Moisture penetration
Which is stronger - a poured concrete wall or concrete block wall of the same dimensions?
Poured concrete wall is stronger
What is spalling?
splitting, chipping, crumbling or splintering or masonry or concrete
4 causes of spalling of foundation masonry
- Moisture penetration
- Low quality concrete
- Masonry not intended for below grade use
- Freeze/Thaw cycles
Difference between a cinder block wall and a concrete block wall
Cinder block is weaker and less moisture resistant than concrete block
Cinder block has a rougher, darker texture than concrete block
Where is mortar deterioration likely to be concentrated?
Lower part of the wall or pier (ie. where rising damp is concentrated)
Causes of rot in wood?
- Surrounding air
- Moisture greater than 20%
- Temperature between 40F (4C) - 115F (46C)
8 causes of pier movement or settling
- Footing missing, undersized, deteriorated
- Soil disturbed, weak, expansive, eroding, freezing/heaving, settling
- Load - snow and ice, building addition
- Poor connection of piers to footings or floor assemblies
- Uneven loading of the pier
- Undersized or overloaded piers
- Deterioration of, or damage to, the pier
- Hollow masonry units installed on their side
2 causes of pilaster pulling from the wall
- Poor installation, footing deteriorating, missing or undersized
- Foundation wall pushing the pilaster away
A series of large voids or bubbles in poured concrete, caused by insufficient consolidation of the concrete before it is cured, is called?
Honeycombing
Piers out of plumb by more than ________ of the pier thickness should be considered unstable
1/3
T or F
Cold joints are never vertical
True
Can be horizontal or diagonal
5 Structural components of floors
- Sills
- Columns
- Beams
- Joists
- Subfloors
2 Functions of floors
- Transferring live and dead loads to the foundation
- Providing lateral support for foundation walls
T or F
Floors will bend a little before they break.
True
T or F
Vertical loads on beams and columns running through the center of the house can be greater than the vertical loads through foundations.
True
Main function of the sill is to
connect top of the foundation to the wood floor system above
Why are rotted sills a problem?
- Rotted sills may be crushed and lead to differential settlement
- May lead to rotted joists and studs
- House frame is will not be well anchored to the foundation
How are sills anchored to foundations?
anchor bolts every 6 feet and within 12 inches of each section of sill plate.
6 common sill problems
- Sills below grade
- Rot or insect damage
- Gaps between the sill and foundation
- Crushed sills
- Not properly anchored
- Missing
Max allowable floor deflections for finished ceilings, and unfinished ceilings below
Finished ceilings - 1/360 of the joist length or 1/2” (whichever is less)
Unfinished ceilings - 1/240 of the joist length
Where beams or joists go into pockets in foundation walls, keep the sides and ends of the wood _____ away from the concrete to allow air circulation and keep the wood dry
1/2”
Nails are good in (shear/tension), but poor in (shear/tension)
Shear (lateral force)
Tension (uplift)
Columns transfer live and dead loads from:
Beams to footings
5 common column materials
- Concrete
- Concrete block
- Brick
- Steel
- Wood
14 common column problems
- Missing
- Settled
- Crushed
- Leaning
- Buckled
- Rust
- Poorly secured at the top or bottom
- Mortar deterioration
- Spalling concrete or brick
- Mechanical damage
- Rot or insect damage
- Heaved
- Prior repairs
- Temporary columns used permanently (CCMC label)
4 causes of column settling
- No footing
- Undersized footing
- Poor soil conditions under the footing
- Larger load than intended
Which column materials are susceptible to crushing
- Concrete
- Wood
T or F
The top of the column should be the same width as the beam it’s supporting
True
3 ways for the steel columns to be fastened to steel beams
- Bolts
- Welding
- Bendable tabs
3 causes of heaving columns
- Expansive soils
- Tree roots
- Frost
Columns are most likely to rot at the top, middle or bottom?
Bottom
Beams can carry load from:
- Floors
- Walls
- Roofs
- Columns
2 most common materials for beams are
- Wood
- Steel
4 types of engineered wood products for beams
- Glulams
- LVL – Laminated Veneer Lumber
- LSL – Laminated Strand Lumber
- PSL – Parallel Strand Lumber
2 areas beams can rest on:
- Foundation
- Columns
The ends of beams resting on masonry or concrete should have at least _____ inches of bearing.
3 1/2”
14 common beam problems.
- Rust
- Rot or insect damage
- Sag
- Poor bearing
- Rotated or twisted beams
- Split or damaged
- Notches or holes
- Poor connections of built-up components
- Weak connections to columns
- Weak connections to joists
- Inadequate lateral support
- Concentrated loads
- Missing sections
- Prior repairs
Beams sag because they are over – _________________. Another way of saying the same thing is that the beam is under – ____________.
spanned
sized
T or F
Steel beams should be shimmed with wood
False
T or F
Wood beams should not be supported directly on hollow concrete block
True
T or F
Joists may sit on top of beams or be attached to the sides of beams.
True
Checking of wood beams results from _______________ and is usually not serious
wood splitting as it dries
T or F
Mortise and tenon joints between joists and beams are stronger than joists supported on top of the beam
False
Columns that rest on the mid-point of beam spans may:
Overstress the beam
Create a concentrated load
Examples of weak joist/beam connection
- Notched joists resting on flange of steel beam
- Mortise and tenon connection
- Notched joists resting on ledger board
6 engineered wood products that can replace conventional joists
- Trusses
- Plywood
- Wood I-joists
- Laminated Veneer Lumber (LVL)
- Parallel Strand Lumber (PSL)
- Laminated Strand Lumber (LSL)
T or F
Joists see vertical loads only
False
T or F
Joists are often used to provide lateral support for solid masonry walls.
True
T or F
Fire-cutting joists is a serious structural error.
True
12 common joist problems
- Rot and insect damage
- Sagging joists
- Poor end bearing
- Rotated or twisted joists
- No blocking, bridging or strapping
- Inappropriate notching or holes
- Split or damaged
- Weak cantilevers
- Weaknesses created by openings around stairs, chimneys and windows, etc.
- Prior repairs
- Concentrated loads
- Missing joists
4 causes of joist sagging
- Overspanning
- Weakened by rot, insects, notches, holes or fire
- Joists installed crown down
- Concentrated loads
Roughly how far can these common joists span if spaced 16 inches apart? Two by Eights __________.
Two by Tens __________.
Two by Twelves __________.
11 1/2 Feet
14 Feet
16 Feet
The joist resting on a beam should not extend past the beam more than 2 inches. Why?
The end of the joist may kick up, creating a high spot in the floor.
Joists typically need _____ inches of end bearing when supported by wood.
1 1/2 inches
7 joist hanger problems
- Undersized
- Inadequate nails
- Wrong type of nails
- Joist not bottomed in hanger
- Joist doesn’t penetrate fully into hanger
- Joists connected to beam at other than 90° with conventional hanger.
- Doubled joists connected to beam with single joist hanger
4 things that can prevent joist twisting.
- Bridging
- Blocking
- Ceilings
- Strapping
T or F
Holes in joists should be near the bottom rather than the middle of the joists.
False
What is a cantilever?
The member is supported at one end and partway along the length. One end is unsupported
Outdoor cantilevers are particularly vulnerable to moisture damage. Where is the problem most likely to occur and why
The problem is most likely to occur where the joists pass through the walls because this is the area that is likely to stay wet.
T or F
Partition walls exert no load on floor joists because they are not load bearing walls.
False
12 common engineered wood flooring problems.
- Holes too big or in the wrong place
- Incorrect joist hangers
- Improper rim joist material
- Missing or incomplete blocking
- Split, notched or cut flanges
- Inadequate end bearing
- Joists beveled or fire cut
- Inadequate blocking on laminated I-joists
- Inadequate bridging or load-sharing
- Trusses that are either too long or too short
- Concentrated loads on the top of trusses
- Trusses installed upside down
3 Functions of joist blocking, bridging , or strapping
- Transferring loads from one joist to adjacent joists
- Damping vibration
- Preventing twisting or rotation of joists under load
4 common subfloor materials.
- Planking
- plywood
- waferboard
- OSB
Disadvantage of diagonal plank subflooring?
Unsupported edges may be springy
T or F
Plywood should be installed with its long dimension parallel to joists
False - perpendicular
9 common subflooring problems
- Rot and insect damage
- Sagging or springy subflooring
- Damaged or cut
- Cantilevered or unsupported ends
- Prior repairs
- Concentrated loads
- Squeaks
- Swollen waferboard
- Cracking ceramic tiles
3 ways to stiffen subflooring below ceramic tiles to prevent tile cracking
- 1 1⁄4 inches of concrete
- Using thicker or double subflooring
- Using blocking to support the subflooring between the joists
T or F
All concrete floors in houses are suspended slabs
False
7 common concrete floor problems
- Cracked
- Settled
- Heaved
- Hollow below slab
- Scaling or dusting
- Spalling
- Rusting reinforcing bar
5 causes of concrete slab settling or heaving
- Footing or foundation settlement
- Soil compaction or erosion below slab
- Excess concentrated loads on the slab
- Footing or foundation heaving due to frost, expansive soils or tree roots
- Soil heaving due to frost or expansive soils
In what part of the building is rusting steel reinforcing bar in concrete slabs likely to be a problem?
Suspended garage floor slabs
