Above ground defects Flashcards
What size cracks are a concern
2mm - Very slight concern
2 to 5mm - slight or aesthetic concern
5 to 15mm - Moderate Concern
15 to 25mm - Sever
over 25mm - very sever with stability concerns
What cracks would you expect to see for foundation or lintel failures
Subsidence
- Vertical cracking to centre of building
or
- Diagonal cracking to corner
- Larger at the top and thinner at the bottom
Heave
- Vertical cracking to centre of building
or
- Diagonal cracking to corner
- Larger at the bottom and thinner at the top
Lintel failure
- Triangular section of brickwork above the windows to drop down creating a triangle crack from the corner.
You are inspecting a building and identify a number of cracks
in the external wall take me through your thought process?
I would firstly note the material the wall is constructed from and what form of
construction the building is.
I would see if any additional loads had been added to the building
I would look to see if there were any drains in the vicinity of the crack
if the crack was serious I would recommend that a structural engineer reviewed it
What could cause leaning and bulging walls
Broken cavity wall ties
Decay of masonry
Increased load
Vibrations
Lack of restraints
What is overloading?
When a wall in subject to more weight or pressure than it was designed to handle
What is frost attack?
It is caused when bricks are saturated and or water has found it way between joints.
water freezes where it expands and then thaws.
this causes stress on the masonry which can lead to spalling.
What is Efflorescence?
White chalky deposit found on brick, masonry and plastered surfaces.
Formed when natural salts and minerals dissolve and water, travel to the surface and then evaporate.
What is wall tie corrosion
Wall ties are essential components that tie the inner and outer leaf of a wall together.
Primary cause is excessive moisture which causes them to rust and loose their strengh
As the metal rusts it expands breaking out their mortar embedment and lead to cracking in the masonry bedding joints.
What are some common stone defects?
Contour scaling
-Type of surface corrosion
Delamination
Wall tie expansion/ ariels
Frost attack
Incorrect bedding
What is cold bridging and how is it eliminated?
A cold bridge is created when materials that are poor thermal insulators come into contact, allowing heat to flow through the path created.
It is remedied by eliminating the cold bridge.
can be done by:
- reducing the cross section
- introducing materials with better insulation properties
- Additional insulation component called a thermal break
