Settlement Part 3
Settlement Part 3
Settlement Part 3
Sands
Maximum total settlement = 40 mm for isolated footings = 40 to 65 mm for rafts
Maximum differential settlement between adjacent columns = 25 mm
Clays
Maximum total settlement = 65 mm for isolated footings = 65 to 100 mm for
rafts
Maximum differential settlement between adjacent columns = 40 mm.
The differential settlement may also be evaluated in terms of the angular
distortion given by: (ΔHdiff) = Δ/L
Where Δ = relative settlement between the two points and L = Horizontal
distance between the two points. Based on a large number of settlement
observations and performance of structures, the suggested limits for tolerable
differential settlements are show in table below.
Angular distortion Type of limit and structure
Cracks
Settlement cracks often occur in the foundation or the house slab or on
the ceilings and walls. Small cracks are often because of minor
foundation settlement or even because of expansion and contraction of
the settlement. Large cracks, however, can represent a more significant
concern. Cracks can warrant concern if they exceed one-quarter of an
inch in width.
1- Tilted Chimney
A tilted chimney is a sign that the foundation of
a building or home has settled; however, it can
be difficult to recognize unless it is severe. A
slight shift in the chimney may not be as
noticeable, but it is a sign of a shifting or
settling foundation.
Examples of prediction of settlement
1 -Gauge the depth of the crack to determine whether it is less than a 1/2-
inch deep. If it is, wear safety goggles, work gloves and a dust mask to
clean the crack using a stiff wire brush and whisk broom, then clean the
area around the crack.
2 -Paint the crack with a latex bonding agent, available at home
improvement stores, to improve the bond when the mortar mix is
applied.
3 -Fill the crack with concrete repair mortar mix, available at home
improvement stores, while the latex bonding agent is still wet. Mix and
apply the mortar according to the label directions on the mix.
4 -Allow the patch to dry and settle for 24 hours. Apply more mortar mix if
necessary and trowel smooth.
5 -Paint the patch and the area immediately surrounding it with a water-
based polyurethane sealer, available at home improvement stores, to
protect the patch from water seepage and staining.
Instructions For Deep Cracks
6- Wear safety goggles, work gloves and a dust mask to clean the crack. If it
is more than 1/2-inch deep and 1 inch wide, use a hammer and chisel to
remove loose chunks of concrete. Be sure to remove all weak areas
around the crack that are crumbling or in danger of breaking off.
7- Use a stiff wire brush to abrade the crack and sweep it out thoroughly to
remove all debris. Paint the crack with a water-based polyurethane
sealer, available at home improvement stores.
8- Fill the crack with concrete repair mortar mix, according to label
directions, while the sealer is still wet. Smooth with a trowel and let it
set for 24 hours. Add more filler, if needed.
9- Paint the patch area and the area immediately surrounding it with a
water-based polyurethane sealer.