A PPT on Stability

1. Building Methods & Construction
Technology
Stability

2. Loading on Parts of a Building
Foundation’s constructed as part of the
building or structure are termed ‘artificial’
foundation, the ground that they are laid
upon is classed as the ‘natural’
foundation.

4. The purpose of a foundation is to spread the
load, from the structure above, over an
adequate bearing area of the subsoil, and
to provide a stable, level base on which to
build.
Although foundations are normally out of
sight, the effect of any movement of a
foundation is likely to be very noticeable in
the structure above.
Purpose of a Foundation

5. The foundation is sandwiched between the forces from the structure
and those from the ground thus subjecting it to compressive forces, so
the foundation must be constructed from a material that is strong
enough to resist any forces being imposed upon it.

6. Loading to the Foundation should
always be equal

7. When constructing stepped foundations, the
construction starts at the lowest level of the site.

8. When using Cavity walling below
ground
• A weak mix concrete is placed in the
cavity to resist Lateral thrust from ground
push.
• Use Ties or not?????

9. • A cavity wall consists of two slender walls If a
load is exerted to one or both of these slender
walls they may buckle or collapse under the
load. If the two leaves are tied together they
will virtually be as strong as a solid wall and
they can support more imposed loadings.

10. • A distance of 150mm max from the edge
of an opening (BR).
• A distance of 225mm max from the edge
of an opening (CoP).
• Vertically spaced at a maximum of 300mm
• 900mm max horizontally (or 750 if cavity is
75mm or more)
• 450mm vertically staggered
Position of wall ties

12. Bonding into Internal walls
Indents And Use of
expanded metal

13. Expansion Joints placed ever 6m

14. Expansion Joint Ties and Sleeves

15. ATTACHING WALLS TO
STRUCTURE (EXTERNAL)

16. Opening in Walls
Any openings
(windows/doors) should be
a minimum of 675mm away
from any external corner of
a building.

17. Lintels
• The constructional member inserted into a wall
to support a load above an opening is called a
LINTEL.
• The imposed loads create stresses upon or
within any lintel, in particular at the top and at
the bottom, which may cause cracking and
failure. The size, shape and design of a lintel
must be such that it can overcome these
imposed stresses and loads.

19. Concrete
Lintels
should
have a
minimum
seating of
100mm

20. Steel
lintels
have a
minimum
seating of
150mm

21. RSJs USBs
must be sat on
a concrete
padstone (min
150mm) and
fixed by means
of rag bolts to
prevent tilt and
slip

22. Fixing Truss to Wall
• Wall plate – Pan bedded
on to ensure level and
parallel
• Fastened to block-work
by Galvanised steel
straps screwed to wall
and wooden Pan set at a
max 1800mm
• Help spread load of roof
through wall on to
foundations

23. • Clip used for fixing truss to wall plate
• Screw
Truss clip

24. Anchor Straps
• Anchor Strap should
fix to at least three
trusses and bed into
block-work this helps
with the roof
structure resisting
the pull of the gable

25. Anchor Straps in Roof construction
• These anchor
ties should be
screwed not
nailed

26. Galvanised Straps for Fixing

27. External Stability
• Piers
Height should not exceed
8 times its minimum dimension
ie: what would be the height of a free standing pier
if it measured 400mmx400mm

28. The purpose of an attached pier is
to :-
• Provide the wall with additional strength to
counter against lateral pressure.
• Accommodate loading and transfer this
load to the walling.

29. Attached piers
• Building Regulations state slender walls should
be supported at corners and at intermediate
lengths i.e. garages conservatories
• Maximum distance between piers =
Every 3m