Overview
Working on an existing building is more demanding than designing a new one. The real strength of the concrete and steel, the actual foundation, and any hidden damage all have to be established first. Only then can a strengthening scheme be designed that solves the problem without creating a new one elsewhere in the structure.
Many buildings need structural work long before the end of their life. Cracks appear, a building changes use, an owner wants to add floors, or an assessment finds members that cannot carry their loads. Retrofitting design works out what the existing structure can safely carry and specifies how to strengthen, repair, or alter it.
When you need it
- An engineering assessment found columns, beams, or foundations that are under capacity.
- You want to add floors that the building was not originally designed for.
- The use is changing, for example from residential to commercial, storage, or production, and the loads increase.
- You can see cracking, exposed or corroded reinforcement, or spalling concrete.
- A renovation needs walls removed, new openings cut, or a mezzanine added.
What's included
- 01
Member strengthening
RC jacketing, steel jacketing, or fibre-reinforced polymer (FRP) wrapping of columns and beams, selected to suit the problem.
- 02
Foundation strengthening
Enlarging or underpinning existing foundations where the soil or the new loads require it.
- 03
Vertical extension design
Checking whether extra floors are feasible, and designing the strengthening needed to carry them.
- 04
Repair specifications
Crack injection, corrosion treatment, and concrete restoration methods specified for each type of damage.
- 05
Alteration design
New openings, removed walls, mezzanines, and other changes designed with safe load transfer.
- 06
Sequencing and temporary support
The order of work and the propping needed to keep the building safe while it is being strengthened.
How it works
- 01
Existing building review
We collect drawings, carry out an as-built survey, and test materials where the records are missing or doubtful.
- 02
Capacity check
The existing structure is analysed to find which members are adequate and which are not.
- 03
Strengthening scheme
Repair and strengthening options are compared for safety, cost, disruption, and buildability.
- 04
Drawings and supervision
Retrofit drawings are issued, and critical stages of the work are inspected on site.
What you receive
- Retrofit drawings
- Strengthening and alteration details for each affected member, with sections and reinforcement.
- Repair method statement
- Step-by-step repair and strengthening procedures, materials, and the sequence of work.
- Capacity calculations
- Checks of the existing structure and of the strengthened design under the new loads.
- Site inspection notes
- Records of inspections at critical stages of the strengthening work.
Codes & inputs
- BNBC 2020Loads and design requirements that the strengthened structure must satisfy.
- Assessment and test resultsFindings of a detailed engineering assessment and material tests on the existing building.
Questions about retrofitting
Can I add floors to a building that was not designed for them?
Sometimes. It depends on the strength of the existing foundation, columns, and concrete. We assess the building, test the materials, and analyse it with the extra floors. The answer may be that it is safe as is, safe after strengthening, or not feasible. Additional floors also need a revised approval from the authority.
Are cracks in my building dangerous?
Not always. Fine cracks in plaster and at wall-to-frame joints are common and usually not structural. Cracks in columns, beams, or slabs, cracks that keep widening, diagonal cracks, and cracks with rust stains need an engineer's inspection. The pattern and location of the cracks show the likely cause and whether repair or strengthening is needed.
Can an existing building be altered or extended?
Often, yes, but it has to be checked first. We review the existing drawings, survey the building, and test the materials where needed to find out what the structure can carry. The alteration or extension is then designed around that capacity, with strengthening where it is required.
