BCT 313 Quiz 3
What is the significance of radon?
Pipes below insulation move air under building out
What is the rule of thumb for tree protection?
Protect under the tree to the edge of the crown which is 1' radius for each 1.5" of the trunks diameter 25" diameter=18ft
What is the reason for 2 inches of concrete covering steel rebar?
Protects against corrosion and concrete spalling
What is the purpose of a sill seal?
Provide capillary break
What is an expansion joint?
Provides a gap between concrete to accommodate concrete volume change. Gap filled with flex seal and backer rod to contain caulk at the top
What is soil testing?
Provides subsurface condition information and data (classification, unit weight, MC) for foundation system design
What is the primary defense against lateral loads?
Rebar
What is top soil?
Surface soil containing organic matter like grass, small roots, and organic nutrients that gets removed from the work area and stockpiled for future use. An excavation contractor may have somewhere for you to put it if you can't store it on site
Temporary Utilities
Temporary utilities should be installed before construction begins. This includes electricity with a generator and a potable water holding tank *This requires planning, contact utility company to extend power line to the site's electrical panel
What is the Angle of Repose?
The angle of the soil that is left after excavating for footing and foundation. There is no science to this angle, just experience of excavators knowing soil types and angle associated with that
R value of Hi-R block
Up to 12 Reduced web so less connection between interior and exterior sides
What is the advantage of welded wire mesh over individual bars of rebar?
economy of labor
Characteristics of submerged crawl space foundation type
- Looks the most normal: siding comes down and stops 10-18" then goes below grade - 4 ft minimum to move around *Typical
Important metrics of footing construction
- Must be below frost line and on undisturbed soil - Placed via batter boards and plumb lines - Check for level and square
What decisions must be made in foundation design regarding the type of foundation?
- Needs and wishes of client matched to site possibilities: based on site contour, soil bearing capacity, local traditions, cost
What is the difference between insulating the interior and exterior of basement walls?
- Not a significant difference in energy use - There can be a thermal bridge but the Delta T is minimal so loss might be acceptable
Construction site planning is required for what?
- Parking for workers -Transportation, delivery, and storage of materials, equipment, machines, trash/recycle
What is the purpose of insulation under the basement slab?
- Prevents heat loss during heating season - Prevents cool slab temperature in warm weather which can cause condensation (mold/moisture problems)
Advantages of rigid insulation exterior surface
- Provides continuous insulation with minimal thermal bridging - Protects below grade sections of insulation - Foundation wall is in conditioned envelope (less heat loss/gain) - No reduction of interior basement floor area
Disadvantages of rigid insulation on interior surface
- Reduced drying capacity if wetting occurs below grade - Reduction of interior basement floor area - Too much traffic= interior wall has to go up to protect it
What are the 5 types of soil and their PSF?
- Rock 12000 PSF - Gravel 6000 PSF - Sand 2000 PSF - Clay 1500 PSF -Organic soils 0 PSF
Continuous footing/strip footing
- Runs all around building - Support bearing walls are sometimes needed in the structure (strip footings)
What is the danger of rebar rusting?
- Rusting is oxidative and the bar thickens and causes cracks in concrete around it
What are the metrics for excavation width?
- Set up and take down formwork - Moisture/water proofing - Positioning stone and drainage tiles adjacent to footing after forms are removed
What are considerations of footing construction?
- Should be continuous to evenly distribute load - Soil-bearing capacity relates to width - Rebar used for loads and soil types - Top of footing must be below frost line
Insulating cores of CMU blocks do what?
- Simplify finishing process because both sides of the block can be exposed - Does not retard the passage of heat through the webs of the block *needs to be continuous layer
What is the purpose of soil testing?
- Soil around and beneath foundations adjusts to loads and all foundations settle to some extent - Uniform settlement causes no harm, differential settlement does cause harm and can be caused by variability of soils (i.e mullins)
What is the purpose of foundation?
- Support various loads of the building - Anchor against wind loads - Protect against frost heaving and expansive soil (clay) - Protect against termites and insects
Column footing
- Supports superstructure above - Doesn't use continuous or strip because they need to be able to move in and around footings - Also uses less concrete
Characteristics of flush crawl space foundation type
- Taller, concrete exposed so addressing siding is important - Done in areas with high water table or ledge issues
Disadvantages of rigid insulation on exterior surface
-Above grade sections are vulnerable - No low permeability materials when finishing walls (polyethylene vapor barrier, vinyl wall covering, oil based paints) - Care must be taken during backfill
Characteristics of slab on grade monolithic foundation type
-Concrete - Underfloor plumbing is a negative -50% of new single-family homes nationally with regional bias - No stem wall - Done in warm climate zones and can be frost protected in cold climates
Disadvantages of ICFs
-Limited exposure to AEC community - UV protection required until Clad - Slopes not possible
What spots are test borings or nuclear gauge readings taken at?
-Location of structure - Drainage points
Steps of perc test
1. Dig hole to bottom where trenches in septic system lead to 2. 8-16ft deep 3. Many professionals observe this because it relates to human health 4. Stick a measuring stick down there and take measurements and call out time *too slow= effluent will stay in the soil *too fast= straight to aquifer too fast
What is a french drain?
A trench filled with gravel/rocks containing a perforated pipe that direct surface water to a storm drain
What is a construction joint?
Accommodate thermal and shrinkage movement (i.e when a pour needs to be stopped at one place and started up again next day)
What is the difference between a barrier and a retarder?
Barrier= nothing gets through Retarder= some things get through
What is the purpose of a sill gaskset?
Capillary break and air sealing
What is used to make sure rebar is in the middle of the slab?
Chairs
PERM ratings
Class I: Vapor impermeable- Very low permeability, sheet polyethylene Class II: Semi impermeability- Low permeability Class III: Medium permeability
What is the result of an organization conflict on site?
Cost increases and production decreases
What is a batter board system?
L shape constructs well outside the footprint to determine where the corner of the building is Strings are run between batter board and marked with screws The intersection of the string is outside corner of the foundation wall Stakes placed at each corner of 3-4-5 triangle *Pythagoras to make sure it is square
What is a failed perc test?
Less than 5MPI, more than 60PMI
What are keyways?
- Inverted trapezoid form that is placed in the footing when it is plastic and left to create notch in form * Resistance to lateral forces
What are the elements of a plot survey?
**Legally binding document by surveyor or engineer - Property line - Setback lines -Existing elevations and contour lines - Point of beginning and bearing degrees (direction it is going) - Length of property line - Scale and North Arrow - Utility locations
Nuances of soil testing
- A small crack of a 1/4'' is okay, the cracks you see can come from wood expansion instead of soil settlement - Can happen with correct soil type if contractor takes out more than they should and try to put it back but doesn't compact it to the same as undisturbed soil
Properties of undisturbed soil
- Air gets in between particles and volume of a given area will expand as much as 50% (so don't try to recover the grade with undisturbed soil) - Under a load it will reconsolidate and cause settling - Needs to be compacted thoroughly when it is used to replace material - 1.5'' stone self compacting -
Before construction begins, how does a contractor determine possible locations for a building?
- Boundary setbacks - Locations of utilities (rural= power, cable, telephone, well water, fossil fuel heating municipal= power, cable, telephone, sewer, water, gas) - Soil test (not usually residentially unless you're in a new area) -Percolation test - Septic system design and location (rural site= artesian well drilled and water tested) - Specify FFEL elevations and building footprint - Driveway footprint - Finished grades, retaining walls, drainage
Characteristics of slab on grade with stem wall foundation type
- Concrete - Underfloor plumbing is a negative - 50% of new single-family homes nationally with regional bias - Plumbing and some electrical underneath
Characteristics of crawl space foundation type?
- Concrete or CMU - Living and storage space not a priority - Wall extends only to frost depth (don't care about extra space) - Floor slab not required- rat slab preferred - 15% of new single-family homes with regional bias - Not easy to move around **short basement
Characteristics of full basement foundation type 1A
- Concrete or CMU - Most common in Northern Regions (already digging to get below frostline so why not get more space?) - Requires headroom for people and utilities and a floor diaphragm on the top
Advantages of rigid insulation on interior surface
- Continuous insulation with minimal thermal bridging - Panels in protected space and can be installed later in construction - EPS can be used instead of XPS (less expensive and recycled!)
What are the loads a foundation must be able to support?
- Dead loads (roof, floor, walls) -Live loads (furniture, snow, people) - Soil and hydraulic pressure - Seismic loads - Wind loads
What are the elements of a plot plan?
- Existing building footprints (FFEL) - Proposed building footprint (FFEL) - Principle landmarks like trees and landscape features - Intended location of septic system and/or well - Location of underground utilities - Driveway footprint, grade, street cut - Finished grade -Drainage -Pedestrian travel options
What decisions must be made in foundation design regarding poured concrete foundations?
- Formwork - Any dimension you want if formworks come in that assembly or custom - Above grade concrete should be smooth surface finish or use patterned forms - CMU is limited to 16x8 unit
What are requirements for full basements?
- Foundation requirements AND - Provide additional living or storage space - Provide mechanical systems space
What decisions must be made in foundation design regarding above-grade aesthetic and finish?
- Foundation wall construction (poured walls or CMUs) - Insulation (material, location, finish) - Below grade moisture protection
Characteristics of full basement foundation type 1B
- Full basement - Originated in Canda 25 yrs ago - Lower labor and costs - <5% in U.S., 20% in Canada
Advantages of ICFs
- Good R Values - Construction time reduction - Combines concrete, reinforcement, insulation, air and vapor barriers/retarders and furring strips
Construction sequence
1. Excavate 2. Footings 3. Wall 4. Formwork 5. Moisture 6. Proof 7. Insulate 8. Drainage and Radon 9. Stone minimum 4" thickness of 3/4" Air barrier and vapor barrier 10. Isolation joint prepped and spaced OR slab is decoupled from floor with vertical insulation 11. Exterior Insulation protected OR finish above grade concrete 12. Sill seal and sill gasket (capillary break) 13. Termite shield (another sill seal or gasket) 14. Framing of first floor diaphragm 15. Backfilling and grading
Construction of footings
1. Pour 2. Vapor retarder 3. Key 4. Vertical reinforcement
What are the steps in the excavation process?
1. Site cleared (stumps and topsoil scraped and stored) 2. Site marked for rough grading and graded 3. Locate footprints of foundation 4. Depth of excavation dictated by design 5. Footing and foundation excavated 6. Sub-excavation soil prep as needed
What are the five characteristics of soil that we care about?
1. Type (see above) 2. Soil-bearing pressure= ability to carry load 3. Expansion coefficients= Clay has a high one 4. Seasonal high-water mark= degree of waterproofing/dampproofing, related to septic design, spring has highest water mark 5. Percolation (test)= Ability to drain water, related to septic design, High perc= straight down to aquifer Low perc= increase septic field area
How tall is the top of the footing
4 ft
How high should a foundation wall go above grade?
6"
Minimum height of foundation
6" above highest grade
Minimum grade slope
6" of drop at 10' from perimeter of building
R Value of CMU with Styrofoam cores
7
Where are anchor bolts placed?
9'' max 12'' max to the end of plate
Where is the top of the footing in New England?
Below the frost line- 4 ft
What is a dry well?
Big hole in the ground filled up with stone and lined with filter fabric (porous to water) to prevent fine particles from soil from clogging up the system after backfill
What is the metric for excavation depth?
Bottom of footing needs to be placed at prescribed code level
What is the difference between damp proofing and water proofing?
Dampproofing is less robust protection from water and used in area where we don't expect much liquid water just moisture in the soil (defending against capillarity)
What is the most common interior insulation?
EPS- higher R and able to be used underground
What is used to establish the right height for excavation?
Elevation benchmarking
What is the minimum width of concrete or masonry footings based on soil loadbearing capacity?
For a 2 story house, the width is typically 19-15 (achieving 1500 which is clay and 2000 PSF which is sand respectively) *increasing width means distributing load over greater area
Why is elevation benchmarking termed "0" or "100"?
For ease of math
What are the types of foundation?
Full basement, crawl space, slab on grade?
What is the purpose of an unbalanced footing?
In a situation where there is a high grade and a retaining wall, the reinforcement resists the overturning moment along with counterweight of footing
What is an isolation joint?
Isolates slab from something else (slab from wall)
What is an anchor bolt and when is it used?
It is a 9'' L shape with a threaded section at the top that attaches to foundation and holds the building down to the foundation. It is used when concrete is still plastic
What is the WorkPoint?
It is the point marked on an adjacent building or temporary post that is used to mark finish floor elevation FFEL. It is based of the certified elevation which is the height above sea level
What is the most important excavation metric?
It needs to be safe enough to work in!
What size stone is required to create a capillary break?
Minimum= 3/4" Stone 1/4" Pore Size
During excavation, what products are used to avoid soil settling?
Rollers or compactors
What does the term "staked out" refer to?
Roughly locating where the building footprint will be. This is usually done with spray paint like on a football field and gets dug out anyway
What are control joints?
Sawed, formed, or tooled groove to regulate location of cracking caused by dimensional changes in the slab
What does differential settlement damage?
Slabs, floors, walls, doors, windows *concrete
What is considered undisturbed soil?
Soil that has not been touched for 10 years
What happens if the soil is SUS?
The soil should be inspected by a soil scientist or engineer to determine capacity of soil to support loads and drainage
R Value of empty 2 cell CMU
Under 3
Residential rule of thumb regarding footing construction
Wall thickness= X Footing thickness= X Footing width= 2X Wall centered on footing
What does the energy code say about flooring?
We have to have subslab insulation