10 Foundations and Concrete Flashcards
1
Q
What should be done before extensive remedial work on a foundation?
A
Ask a structural engineer to evaluate your foundation
This includes assessing signs of distress like bowing, widespread cracking, uneven settlement, or chronic wetness.
2
Q
What is the role of a foundation?
A
It mediates between the loads of the house and the soil on which it rests
3
Q
What are signs of distress in a foundation?
A
- Bowing
- Widespread cracking
- Uneven settlement
- Chronic wetness
4
Q
What is a tee (or spread) foundation?
A
A commonly used foundation type with a cross section resembling an inverted T
5
Q
What is required for foundations in areas where the ground freezes?
A
Footings must be dug below the frost line
6
Q
What is a slab on grade foundation?
A
A giant pad of reinforced concrete poured with a thicker perimeter footing
7
Q
What is the primary disadvantage of drilled concrete piers?
A
Cost and access
8
Q
What do driven steel pilings do?
A
Anchor foundations on steep or unstable soils
9
Q
What is the function of steel reinforcing bar (rebar) in foundations?
A
Carries and distributes loads, reducing the likelihood of point failure
10
Q
What can excessive water around a foundation cause?
A
- Damp basements
- Rotting framing
- Foundation cracking
11
Q
What are common indoor symptoms of foundation failings?
A
- Localized springiness or low spots in flooring
- Widespread springiness in floors
- Cracking at the corners of openings
12
Q
What are the characteristics of narrow vertical or diagonal surface cracks?
A
They are likely caused by foundation settlement or soil movement but are probably not serious.
13
Q
What indicates a large vertical crack through the foundation that is wider at the top?
A
One end of the foundation is sinking, typically at a corner with poor drainage.
14
Q
What does horizontal cracking in a concrete foundation usually indicate?
A
Lateral pressure from water-soaked soil
15
Q
What is jacking in the context of foundation repair?
A
Raising or lowering a building to repair or replace defective framing or failed foundations
16
Q
What is shoring?
A
A temporary system of posts and beams that support building loads
17
Q
Fill in the blank: A well-designed foundation keeps a house’s wood underpinning above the soil to prevent it from _______.
A
rotting or getting eaten by insects
18
Q
True or False: The drainage system is technically a part of the foundation.
A
False
19
Q
What is a key factor in determining the type of foundation to use?
A
Soil conditions and intended function (basement or crawl-space)
20
Q
What are the typical compressive strengths of concrete used in residential foundations?
A
2,500 to 3,500 pounds per square inch (psi)
21
Q
What can cause widespread springiness in floors?
A
Joists that are too small for a span or a failed or absent girder
22
Q
What should be done if a foundation crack is suspected to be active?
A
Epoxy a small piece of glass to both sides of the crack
23
Q
What are some methods to mitigate moisture problems around a foundation?
A
- Keeping gutters and downspouts clear
- Grading soil away from the foundation
- Improving drainage around basement window wells
24
Q
What is shoring?
A
A temporary system of posts, beams, and other structural elements that support building loads temporarily between jackings.
25
What should be done after repairs are complete when using shoring?
Lower the house and remove the shoring as soon as possible.
26
Why is jacking a house considered nerve-wracking?
It requires a deep understanding of house framing and how structures transfer loads.
27
What type of contractors typically subcontract house-raising tasks?
Foundation contractors subcontract to house movers.
28
What is the purpose of using 4x4 posts and 4x8 or 4x10 beams for shoring?
To support a single-story house adequately.
29
What type of wood is recommended for shoring due to its compressive strength?
Douglas fir, oak, or wood with similar compressive strength.
30
What is cribbing?
A framework of usually squared timber stacked in alternate layers to create a stable platform for jacking or shoring house loads.
31
What are the three main types of crack-repair materials?
* Cement-based
* Epoxy
* Polyurethane foams
32
What is the recommended first step when patching foundation cracks?
Determine the cause of the crack and fix it first.
33
What is the compressive strength of injected epoxy according to Simpson Crack-Pac® after seven days?
11,000 psi.
34
What is a disadvantage of using epoxy for crack repairs?
It takes hours to harden and can ooze out if there's a void between the soil and foundation wall.
35
What is the primary advantage of polyurethane foam for crack repairs?
It sets up in minutes and stays flexible.
36
What is a safety precaution to take when using jacks?
All jacks must be placed on a stable jacking platform and plumbed.
37
What type of jacks are commonly used for house-raising?
* House-raising screw jacks
* Hydraulic jacks
38
What should be done if excavation is necessary during jacking?
Have a plan for who will do it and where to put the displaced dirt.
39
True or False: Hydraulic jacks can be lowered incrementally.
False.
40
What is the rule of thumb for placing jacks or shoring platforms near an excavation?
Move back 1 ft. for each 1 ft. dug down.
41
What should be done if the soil where jacking occurs is not level?
Dig a level pit for the jacking.
42
What are some conditions that make raising houses difficult?
* Sloping sites
* Unstable soil
* Site erosion
* Excessive ground water
* A masonry building
* Multiple-story houses or heavy single-story dwellings
43
What type of braces and connectors are used to keep posts plumb?
* Diagonal 2x4 braces
* Plywood gussets
* Metal connectors
44
What is the maximum height you should raise the threaded shaft of a screw jack?
No more than three-quarters its total length.
45
What is the purpose of footing blocks under each post?
To support the posts adequately and prevent deflection.
46
What is the rule of thumb when digging down for jacking?
Move back 1 ft. for each 1 ft. you dig down.
47
Why should jacks or shoring not be placed where they could be undermined later?
To prevent instability and potential injury.
48
What should be done to ensure posts are level and plumb?
Cut the ends of the posts perfectly square and check for plumb periodically.
49
What is the purpose of digging a level footing pit?
To prevent footings or cribbing from migrating under pressure.
50
What should be checked daily for plumb and level during jacking?
Jack supports and shoring.
51
What can be used to help keep posts plumb?
Diagonal bracing, plywood gussets, and metal connectors.
52
How should jacks be raised to minimize damage to finish surfaces?
In small increments, such as 1⁄4 in. per day.
53
What is a common method for positioning jacks and jacking beams?
Position them as close as possible to the joists, girders, or stud walls.
54
What is the recommended size for jack bases?
Each jack base should be about 2 ft. by 2 ft.
55
What should be done when replacing a mudsill or sections of a foundation?
Place a 4x8 or 4x10 carrying beam on edge under the joists.
56
What is necessary when joists run parallel to the foundation wall being replaced?
Run needle beams through exterior walls and support each beam with posts.
57
What is the purpose of doubling the rim joist when jacking?
To prevent deflection under load.
58
What should be done after jacking is complete?
Install shoring posts for greater stability.
59
What is the procedure for removing shoring?
Reinsert jacks and raise them slowly and evenly to take weight off the shoring.
60
What is typically included in minor repairs?
Anything short of replacing a failed foundation.
61
What is a common cause of wooden post failure?
Moisture wicking up through a concrete pad.
62
What should be used to prevent a new post from rotting?
A 22-ga. sheet aluminum plate under the bottom of the post.
63
What is the purpose of isolation joints in load-bearing pads?
To separate pads from floors.
64
What safety equipment is necessary when cutting concrete?
Safety glasses, gloves, hearing protectors, and a respirator mask.
65
What should be done if a new foundation section isn’t long or deep?
Use an electric demolition hammer with a shovel bit to excavate the trench.
66
How thick is a typical concrete floor poured before the 1950s?
3 in. to 4 in.
67
What type of saw is recommended for cutting concrete to minimize dust?
A gasoline-powered wet-cut saw.
68
What should be checked for solid blocking or cross bridging?
Look under the house before adding a girder to correct springy floors.
69
What is the typical span for a 2x10 joist?
12 ft.
70
What is the typical span length for joists?
2, 6, 8 ft.
## Footnote
Typical spans can vary based on the type of joists and loads.
71
What should you check before adding a girder to correct springy floors?
Check for solid blocking or cross bridging between joists.
## Footnote
If absent, adding blocking may stiffen the floors.
72
What are the dimensions for load-bearing pads supporting a two-story house?
30 in. by 30 in. by 18 in. deep, reinforced with two layers of No. 4 rebar.
## Footnote
Each layer has three pieces of rebar positioned perpendicularly.
73
What is the recommended curing time for concrete pads before placing weight on them?
Three days minimum, seven days recommended.
## Footnote
Curing helps achieve the required strength.
74
What is the purpose of adding a girder under a run of joists?
Shortens the distance they span, stiffens a springy floor, and reduces loading on perimeter foundations.
## Footnote
It is essential when joists exceed rule-of-thumb lengths.
75
How should a girder be installed if it has a crown?
Install it so the crown faces up.
## Footnote
This helps maintain proper load distribution.
76
What is the recommended nailing schedule for built-up girders according to the Uniform Building Code?
20d nails at 32 in. on center at the top and bottom, two 20d nails staggered at the ends and at each splice.
## Footnote
This ensures structural integrity.
77
What is the weight of a W12x26 I-beam?
26 lb./ft.
## Footnote
For a 22 ft. span, the total weight is 572 lb.
78
What should be done before replacing a shallow foundation?
Check local building codes for foundation specs and survey for obstructions.
## Footnote
Ensure to plan for temporary supports.
79
What materials are recommended for new mudsills?
Foundation-grade heart redwood, pressure-treated Douglas fir, or yellow pine.
## Footnote
These materials resist insects and moisture.
80
What tools are recommended for breaking out an old foundation?
A 9-lb. sledgehammer, a 6-ft. pointed steel bar, or a jackhammer.
## Footnote
A gas-powered saw can also be used for cutting.
81
Fill in the blank: The girder should run beneath the ______ of the joist span.
midpoint
82
True or False: Steel beams provide less strength per equivalent depth than wood beams.
False
83
What should be done if the bottom of many studs is rotted?
Install a thicker mudsill to compensate for the cut-off.
## Footnote
This helps maintain structural integrity.
84
What is the purpose of using plywood gussets at girder joints?
To join posts to beams for structural support.
## Footnote
This is often required by building codes.
85
What should be done if the first stud chatters while cutting?
Tack furring strips to all the studs above the cut-line.
## Footnote
This stabilizes the studs for cutting.
86
What is the primary method for leveling a house?
Using a unified hydraulic jacking system
87
What does a unified hydraulic jacking system allow for?
Interconnected jacks monitored by a central console
88
Who determines the desired height for leveling a house?
Foundation contractor, house mover, structural engineer, and occasionally the architect
89
What is a master reference point used for?
To determine if house corners need raising or lowering
90
What common damages can occur when leveling a house?
* Cracked plaster
* Popped drywall seams
* Misaligned door latches
* Askew trim
* Binding windows and doors
91
What might be more cost-effective than perfectly leveling floors?
Raising only the most out-of-level areas
92
What is the purpose of a laser level in foundation work?
To transfer the height of the new foundation
93
What is the role of a jackhammer in foundation work?
To bust concrete
94
What is a method for cutting concrete if rebar is encountered?
Using an acetylene torch or a metal abrasive wheel
95
What are the primary components of concrete formwork?
* Joists
* Form boards
* Rebar
* Blocking
* Mudsill
* Anchor bolts
96
What is the recommended spacing for 2x4 form-hangers?
Every 32 inches
97
What should be done to ensure formboards are properly positioned?
Use diagonal braces to keep them plumb
98
What is the flush position of a foundation wall traditionally aligned with?
The edge of the house framing
99
What is the purpose of form ties in concrete formwork?
To space the formboards the correct distance apart
100
What should be done to formboards before pouring concrete?
Spray with form-release oil
101
What types of structural steel are used in renovated foundations?
* Rebar
* Anchor bolts
* Pins (or dowels)
* Metal connectors
102
What is the most common rebar size used in residential construction?
No. 4 (1/2 inch in diameter)
103
How should rebar be placed in foundations?
Back 3 inches from forms and at least 3 inches above soil
104
What is the maximum spacing for anchor bolts in one-story foundations?
6 feet apart
105
What should be used for maximum grip when placing anchor bolts?
Square washers
106
What is the recommended drill size for holes when retrofitting anchor bolts?
1/8 inch larger than the diameter of the bolt
107
What is the purpose of epoxy when retrofitting anchor bolts?
To secure the bolts in the concrete
108
Fill in the blank: The outer formboards are supported by _______.
[plumbed 2x4 form-hangers]
109
What size holes should be drilled for a 5/8-in. all-thread rod?
3/4-in. holes
## Footnote
Drill holes 1/8 in. larger than the diameter of the bolt.
110
What is the compressive strength of epoxy compared to concrete?
Roughly four times greater
## Footnote
Epoxy's bond strength is generally stronger than mechanical bonds.
111
What are cold joints in concrete?
Weak points where new concrete is butted against old or where separate pours create seams.
112
What is the purpose of rebar pins in concrete?
To join cold joints and prevent separation.
113
What diameter holes should be drilled for 1/2-in. rebar?
5/8-in. holes.
114
How far should rebar be embedded into the top of foundations?
At least 7 in.
115
What should be done before nailing up the mudsill?
Predrill for anchor bolts.
116
What is the recommended number of nails to end-nail the mudsill to the studs?
Two 16d nails per stud.
117
What must be done to clean holes before applying epoxy?
Use compressed air and a hole-cleaning brush.
118
How should epoxy be filled into the holes?
From the bottom with a long-nozzle injector.
119
What should you do if no epoxy oozes out of the top of the hole?
Leave the failed bolt in place and drill a new one next to it.
120
What is the minimum cure time for concrete before removing forms?
Three days.
121
What is the purpose of a moisture barrier in a concrete slab?
To prevent moisture from penetrating the concrete.
122
What thickness of rigid insulation is typically recommended under slabs?
2 in.
123
What is the main ingredient in concrete?
Portland cement.
124
What is the effect of a lower water to cement ratio on concrete strength?
It makes the concrete stronger.
125
What materials are typically used to reinforce garage floors?
Steel mesh or rebar.
126
What is the recommended action if the concrete begins to set?
Pull out the perforated steel stakes holding the bottom formboards.
127
What should be done after pouring concrete to remove air pockets?
Use a concrete vibrator.
128
What height must a new cap be above grade when capping a foundation?
8 in.
129
What are the two options for raising a house without pony walls?
Grade the soil away or jack up the house.
130
How much does concrete weigh per cubic yard?
About 2 tons.
131
What should you do if you need to move and smooth a slab that requires 10 cu. yd. of concrete?
Get plenty of help.
132
Fill in the blank: The top of the form should be slightly higher than the bottom of the _______.
mudsill.
133
True or False: Epoxy bonds are generally weaker than mechanical bonds.
False.
134
What is the recommended overlap for rebar splices?
At least 12 in.
135
What is the purpose of a pneumatic nailer when attaching the mudsill?
To end-nail the sill to the studs.
136
What should be done with the nuts on anchor bolts after the mudsill is attached?
They should be just snug until the concrete cures.
137
What is the consequence of leaving perforated steel stakes in concrete until the next day without oiling?
They will likely be difficult to remove.
138
What is the purpose of the blow-brush-blow cleaning cycle?
To thoroughly clean the holes before applying epoxy.
139
What type of concrete pump hose is easier to handle?
A 2-in. hose.
140
What must be done to the existing mudsill when capping a foundation?
It must be removed.
141
What is the weight of concrete per cubic yard?
About 2 tons per cubic yard.
142
What is the minimum thickness for a plastic barrier under the slab?
6 mil.
143
What is the primary purpose of a 2-in. concrete-pump hose?
To allow for easier movement and control of the pour.
144
What should be done to steel reinforcement before pouring concrete?
Elevate it on dobie blocks or wire high chairs.
145
What is the purpose of snapping level chalklines on the walls or forms?
To indicate the final height of the slab.
146
How do you establish screed levels for a slab?
Create wet screeds around the perimeter and one in the middle.
147
True or False: Screeding is typically a two-person operation.
False.
148
What tool is used to smooth the concrete after screeding?
A magnesium bull float.
149
What should be done after bull-floating concrete?
Wait for the water to evaporate before finishing.
150
What indicates that the concrete is ready for troweling?
A test knee board leaves only a slight indent.
151
What is the recommended action if the knee board sinks more than 3/4 in.?
Wait a bit longer before troweling.
152
Fill-in-the-blank: Concrete takes _____ to cure fully.
a month.
153
What is the purpose of insulating basement floors and walls?
To prevent moisture from condensing on cool surfaces.
154
What materials should not be in direct contact with concrete due to moisture concerns?
Wood, paper-faced drywall, and fiberglass insulation.
155
What is an effective way to reduce condensation in a basement?
Install rigid foam panels.
156
What should be done with gutters and downspouts to prevent water issues?
Position and maintain them to direct water away from the house.
157
What type of dehumidifier is recommended for a basement?
One that can run continuously during peak humidity.
158
What should be done to prevent mold in a dehumidifier?
Drain it daily and scrub it periodically.
159
Fill-in-the-blank: To estimate cubic yards of concrete, calculate width x length x depth and divide by _____.
27.
160
What is the purpose of a check valve in a sump pump system?
To prevent backflow of water.
161
What should be done to cold-water pipes to reduce condensation?
Wrap them with preformed foam pipe insulation.
162
What is the best way to ensure insulation is airtight?
Use tightly sealed EPS panels.
163
How can you test for condensation issues in a basement?
Use a piece of aluminum foil taped to the foundation.
164
What can excessive moisture from undervented kitchens and bathrooms lead to?
Moisture migration to the basement.
165
What should be done if water migrates through foundation walls?
Consider remedial options for correction.
166
What is a recommended method to vent moisture from basements?
Add exhaust fans to vent them properly.
167
How should gutters and downspouts be positioned?
They should direct water away from the house.
168
What are the three remedial options for correcting water migration issues?
* Remove water once it gets in
* Fill interior cracks, seal interior surfaces, and install a vapor barrier
* Excavate foundation walls, apply waterproofing, and improve drainage.
169
What is the best means of removing water from a basement?
Sump pumps.
170
What is the size of the sump pit recommended for water collection?
18 in. to 24 in. across.
171
What are the two types of sump pumps?
* Pedestal sump pumps
* Submersible sump pumps.
172
What type of discharge pipe is recommended for permanent sump pumps?
11⁄2-in. rigid PVC discharge pipes with a check valve near the bottom.
173
How far should discharged water be directed from the house?
At least 20 ft. from the house.
174
What is the first step in applying interior solutions to damp basement walls?
Fill cracks and apply damp-proofing coatings.
175
What type of coatings can withstand higher hydrostatic pressures?
* Cementitious coatings
* Epoxy-based coatings.
176
What type of insulation panels might be better for allowing moisture to pass in basements?
Semipermeable, moisture-tolerant insulation panels.
177
What are the first steps to waterproof exterior foundation walls?
* Excavate foundation walls
* Upgrade perimeter drains.
178
What is the typical thickness for sprayed liquid membranes?
40 mil.
179
What is a popular solvent-based waterproofing membrane?
Modified asphalt.
180
What are the advantages of water-based membranes?
* No strong odor
* Not flammable
* Won't degrade rigid foam insulation.
181
What type of membranes are typically thicker and more durable?
Peel-and-stick membranes.
182
What are air-gap membranes used for?
Create an air-drainage gap to help water drain away.
183
What is Bentonite and how does it function in waterproofing?
A volcanic clay that swells when wet to keep water away from foundation walls.
184
True or False: Cementitious coatings are flexible and do not crack.
False.
185
Fill in the blank: The ideal slope for soil around the foundation should be _______.
away from the house.
