Settlement of buildings
Contents |
[edit] Introduction
Settlement is the downward movement of the ground caused by a load consolidating the soil below it or causing displacement of the soil. Settlement often refers to the downward movement of the ground around an excavated space, such as that for tunnels, shafts, or basements.
It is usual for buildings to experience some degree of settlement within the first few years after construction. Although the extent to which this ground movement impacts upon buildings depends on several factors, which may include:
- Existing soil conditions.
- Methods of construction.
- Size and depth of the construction works.
- Type of structure, its condition, and its foundations.
The impact of settlement is opposite to the effect of heave which is the upward movement of the ground, and is different from subsidence which occurs where soil is unstable and sinks downward without any imposed load.
[edit] Causes of settlement
Typically, settlement occurs within the foundation soils that surround and support the structure.
The more common causes of settlement include:
[edit] Weak bearing soils
Where soils are not capable of supporting the weight or bearing pressure exerted by a building’s foundation. This can occur when foundations are designed based upon general guidelines rather than site-specific soil information, such as in the case of some residential construction projects.
[edit] Poor compaction
The leveling of a site prior to foundations being constructed often relies upon the placement of fill soils. Often these are imported from off-site locations and unless they are properly placed and compacted, may compress under loading and result in settlement of the structure.
[edit] Changes in moisture content
The soil’s ability to support the load of a foundation settlement may be reduced by changes in moisture content within the soil. If soils are saturated, clays and silts may be softened. If soils are dried-out they have a tendency to shrink or contract.
[edit] Maturing trees and vegetation
Therefore, a common cause of settlement is root systems expanding from maturing trees and vegetation and drawing soil moisture from beneath a structure. A general rule is that the diameter of a tree’s root system is at least as large as its canopy.
[edit] Soil consolidation
Applied loads force water out of clay soils which compress and result in downward movement or settlement of overlying structures. Settlement caused by consolidation may take a considerable amount of time to be ‘complete’.
[edit] Signs of settlement
In cases of minor settlement, which could be due to cyclic or seasonal movement, small hairline cracks may appear in plaster. In more serious cases, doors and windows may develop sticking problems, and plumbing and mechanical equipment may be adversely affected.
It is rare for settlement to affect the structure of the building. Whilst situations vary from site to site, a general rule is that a crack is considered to be of a structural nature if it approaches or exceeds a width of one-quarter inch.
[edit] Responding to settlement
There are certain steps that may be taken to prepare for, and respond adequately to, settlement:
- Site investigations can be undertaken to try and find out how much settlement is likely and the potential effect on buildings.
- Actual ground and building movement can be measured.
- The existing conditions of buildings and how they may be impacted by further settlement can be assessed.
- Footings may be designed to spread loads over weak soils, reducing potential foundation settlement.
- Compensation grouting can be used to treat ground. This technique is a commonly-used on tunneling projects, where grout is injected into the ground to firm up the area of settlement.
[edit] Related articles on Designing Buildings Wiki
- Bearing capacity.
- Brownfield land.
- Building on fill.
- Cracking and building movement.
- Defects in brickwork.
- Defects in construction.
- Defects in stonework.
- Driven piles.
- Foundations.
- Ground conditions.
- Ground heave.
- Ground improvement techniques.
- Groundworks.
- Latent defects.
- Lateral loads.
- Leaning Tower of Pisa.
- Movement joint.
- Remedial works.
- Spalling.
- Subsidence.
- Types of structural load.
- Underpinning.
[edit] External references
Featured articles and news
Boiler Upgrade Scheme and certifications consultation
Summary of government consultation which closes 11 June 2025.
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
From project managers to rising stars, sustainability pioneers and more.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.
Construction Products Reform Green Paper and Consultation
Still time to respond as consultation closes on 21 May 2025.
Resilient façade systems for smog reduction in Shanghai
A technical approach using computer simulation and analysis of solar radiation, wind patterns, and ventilation.