What is the purpose of ‘Footings’?
To receive loads through posts or foundations walls to transmit them to the soil.
What is important to consider for footing sizing?
- A soil test must be done beforehand.
- Sizing is done by a structural engineer.
- Must be below the frostline.
A footing is made up of what material?
Poured concrete or wood.
Here are some things to consider for ‘Footings’
-Undisturbed soil, rock, compacted granular fill ( When soil is taken out, properties of soils are now different )
- Drainage
- Insulation
- Key or re-bar to resist lateral pressure, bonds footing to foundation wall
Define ICF
Insulated Concrete Formwork
True or False. Foundations supports building loads including snow and occupant loads.
True.
Name a few materials used for formwork.
- Steel
- Plywood
- Plastic sheets
What are anchor bolts used for?
To hold sill plates in place. ( 1/2” dia. max 8’ apart; embedded minimum 4” in concrete; bent to provide maximum bond )
What do we used to reinforce concrete foundations?
10mm bars @ 600mm made of steel, glass or plastic fibres.
What are some components of ICF?
- Replaces conventional systems
- Made of polystyrene
- Proprietary systems, plastic clips hold rebar in place
- Ultra efficient
- Expensive but payback period is short
- Must add a membrane on the exterior
Describe Basement Slabs.
- Generally 4” thick
- Sloped towards drain
- Reinforcing mesh
- Typically to prepare for the basement slab, 4” ( 100mm ) minimum of 3/4” ( 19mm ) crushed stone is compacted over the subsoil as a drainage layer to keep water away from the underside of the slab.
- Put coarse gravel and a polyethylene vapour diffusion retarder under a concrete slab to keep water vapour and water in the ground from getting into the slab from underneath.
- Pyrite
Describe ‘Foundation Wall Drainage’
- Foundation drainage normally consists of a drain tile installed around the perimeter of the basement and a wall drainage layer ( also known as a drainage mat )
- The perforated drain tile is usually 4” in diameter and is laid at the level of the bottom of the footing. The tile is wrapped with a geotextile fabric to keep out of the fine soil particles.
- The tile is then covered with min. 6” (150mm) clean gravel or crushed stone.
- This tile is then connected to basement sump pump.
Describe Radon and Soil Gases
- Radon is caused by the decomposition of soils that contain uranium
- Radon is radioactive, colourless and tasteless, and can cause lung cancer
- Keeping soil gas ( radon, water vapour, herbicides, termiticides, methane, etc. )
- Soil gas moves due to pressure differences
- Since we cannot eliminate the holes, the best thing we can do is control the pressure.
- The granular fill located below the concrete slab can be integrated into a sub-slab ventilation system to control soil gas migration by creating a zone of negative pressure under the slab.
- A vent pipe connects the gravel layer to the exterior through the roof.
Define WWF
Wielded Wired Mesh
Name the 4 sources of moisture.
- Rainwater draining from a roof
- Rainwater entering the ground
- Natural springs in the ground
- Ground water table
Describe what is ‘Water Vapour’
- Water vapour flows from warm to cold
- Water vapour dries through a process called evaporation
Definition: Particles of liquid moving from an area of higher concentration to one of lower concentration.
Describe basements, water managed foundations.
- Keep rainwater away from the foundation wall perimeter.
- Drain groundwater with sub-grade perimeter footing drains before it gets to the foundation wall.
What is Iron Ochre?
Iron ochre is a bacteria present in soils that are generally sandy and rich in oxygen. The bacterium appears as a slimy paste that clogs drains and prevents them from functioning properly. ( due to geotextile membrane )
Waterproofing vs Dampproofing
- Waterproofing relies on creating a watertight barrier without holes
- Waterproofing seeks to prevent the passage of water through the basement wall by the application of a waterproof membrane.
- Damproofing protects foundation materials from absorbing ground moisture by capillarity.
- Dampproofing is not intended to resist groundwater forces ( hydrostatic pressure )
- If water management is used, waterproofing is not necessary
- However, control of capillary water is still required ( dampproofing )
- Dampproofing is typically provided by coating the exterior of a concrete foundation wall with a bituminous paint or coating
- This coating is usually spray-applied or applied with a brush.
- A waterproof membrane could be applied to foundations in situations where drainage and dampproofing cannot provide sufficient protection such as in areas with high water tables.
- The most commonly used are liquid-applied membranes or peel-and-stick sheet membranes.
Describe a Drainage Mat.
A drainage mat is a manufactured product made of a loose mat of stiff, inert fibres, a plastic egg-crate structure or some other very open porous material. It is faced on the outside with a filter fabric that prevents fine soil particles from entering and clogging the drainage passages in the mat.
- Any subsoil water that approaches the wall falls through the porous material of the mat to the drain pipe at the footing.
Describe ‘Foundation Insulation’
- Minimum 600mm below grade, inside or outside
- Insulation on the outside reduces the temperature swing that the foundation wall experiences which often reduces thermal stresses and cracking that results.
