The principals of foundations

The principals of foundations

To help you understand the basics of foundations

Aims of the lesson

• To explain the purpose of foundations

• To identify which type of foundation should be used and why

Objectives of the lesson

• Determine the need for foundations.

• Compare different foundations

• Establish which type of foundation should be used in different circumstances

• Calculate volumes

Foundation's

There are many types of foundation. Differing ground conditions, proximity of trees, backfilled land, soil types, proximity of drains, wind speeds, all dictate the form our foundation work will take

Substructure.

• The sub structure is classed as anything below ground level.

• This goes up to and includes the D.P.C.

• The substructure safely transfers the loads from the building to keep them stable and free of subsidence.

Superstructure

• The superstructure is everything above the D.P.C.

• Dead loads

• Imposed Loads

What do we mean by the dead load?

• The dead load is the actual weight of the building

Can you define an imposed load?

• Furniture

• Kitchens and bathrooms

• Weather

Multiple Choice

The D.P.C. is part of which?

• Substructure

• Superstructure

Multiple Choice

Is your bed

• An Imposed load

• A dead load

Poll

OBJECTIVE 1

Do you now understand the need for foundations?

• YES

• NO

Types of Foundations

• Strip foundations

• Raft foundations

• Pad foundations

• Piled Foundations

• Stepped foundations

Narrow strip foundations

The most common sort of foundation, used for small domestic dwellings and low rise structures.

The trench is filled with concrete usually to within 4-5 courses of the D.P.C.

The minimum depth from the bottom of the trench to ground level should be 1 metre.

Raft Foundation

• One slab of concrete which covers the entire base of the building.

• Used when the soil is weak

• The outside of the raft is dug deeper to help protect the raft

Pad foundations

• Used mainly in buildings with brick or steel columns

• Reinforced concrete beams can be laid in between the pads to support the walls

• The depth of the pad depends on the size of the structure

• Reduces the amount of excavation required

Piled foundations

• Holes are bored up to 4 metres deep and between 250-350 mm wide

• Reinforced steel bars are set in the concrete

• Used in high rise or skyscrapers

Stepped foundations

• Used on sloping ground

• Each step should be set equally to brickwork courses

• 
  

Poll

OBJECTIVES 2&3

Would you now be able to know the difference in foundations and why they are used?

• Yes

• No

Concrete Ingredients

• Cement (Portland stone)

• Aggregates (Fine or course)

• Potable water

• Additives

Calculating volumes

• The steps for calculating volumes

• Measure the width, length and multiply these together

• Now multiply this by the height

• This will give you the cubic measurement or volume required

Work out the volume

Width = 5 metres

Length = 10 metres

Height = 2 metres

Multiple Choice

The volume in cubic metres would equal

• 50 m3

• 200 m3

• 120 m3

• 100 m3

Poll

OBJECTIVE 4

Do you now understand how to calculate volumes

• YES

• NO