Buying a Flat in Bangladesh? What to Check About the Building's Structure First

Buying a flat is the largest purchase most families in Bangladesh ever make. Buyers spend weeks comparing locations, layouts, prices and finishes, and rightly have the title documents checked by a lawyer. Far fewer ask how the building itself was designed and built, even though every flat in it depends on the same columns, beams and foundations, and the building will be home for decades.

This article sets out what to check about the structure before you buy, whether the building is new, under construction or second-hand. It is general guidance from a structural engineer's point of view, not legal advice.

Step 1: Ask for the documents

A developer or owner who had the building properly designed and approved will normally be able to show these. Their absence is not proof of a problem, but it is a reason to look harder.

Document	What it tells you
Approved building plan (from RAJUK, CDA, KDA or the local authority)	That the design was submitted and approved, and for how many floors and what use
Occupancy certificate, where issued	That the authority accepted the completed building for use
Structural drawings and the structural engineer's name	That a structural engineer designed the building, and who is accountable for the design
Design code and design basis	Which code was used (BNBC 2020, 2006 or the 1993 code) and the seismic zone, soil and loads assumed
Soil investigation report	That the foundation was designed for the actual ground
Concrete and rebar test records from construction	Whether the materials met the specification as the building went up
Supervising engineer's details	Who checked the work on site

The single most useful check: compare the number of approved floors with the number of floors that stand. Floors added beyond the approval are common in Bangladesh and they add load to columns and foundations that were not designed for it.

Step 2: Look at the whole building, not only the flat

Most buyers inspect the flat they are buying. The structural risks are usually elsewhere. Walk through the ground floor, the stairs, the roof and, if you can, a few other flats.

The ground floor

• Is it an open parking floor with few walls under floors full of brick walls? That is a soft storey, the most common serious earthquake weakness. Ask how it was dealt with in the design. See soft-storey buildings.
• Do any columns stop at the first floor and sit on beams (floating columns) to make parking space? They need special design.
• Are the parking-floor columns noticeably slender for the height of the building?
• Are there cracks at the tops or bottoms of columns, or in the beams over the parking bays?

Throughout the building

• Cracks: diagonal cracks in walls, cracks in columns and beams, cracks along bars with rust stains. See which cracks are dangerous.
• Damp and stains on ceilings under bathrooms and kitchens, and on the top-floor ceilings under the roof.
• Balconies and sunshades: do their edges droop? Any cracks across the top where they meet the wall?
• Alterations: walls removed, columns notched, openings cut through beams, extra rooms on the roof.
• The roof: water tanks, rooftop rooms and gardens add weight; ponding water and thick old screeds suggest leaks and extra load.
• The building's relation to its neighbours: built wall to wall with floors at different levels, or separated by a gap?

Inside the flat

• Columns: are they the same size on your floor as shown on the drawings? Are there cracks at their tops?
• Ceilings: any visible sag across a large room, or cracks in partitions under the slab? See slab deflection.
• Bathrooms: damp patches in the walls behind, or stains below in the flat underneath (ask the downstairs owner).
• Doors and windows that jam, floors that slope.
• Fresh plaster or paint in patches, which can hide repairs. Ask what was repaired and why.

Step 3: Ask the developer the right questions

• Who was the structural engineer, and is the design to BNBC 2020?
• Which seismic zone and soil conditions was the building designed for?
• Was a soil investigation carried out, and what type of foundation was used, piles or footings?
• Who supervised construction, and were concrete cylinders or cubes tested at each casting? Can you see the results?
• Is the building built to the approved number of floors and use?
• Have any structural changes been made since completion?
• Is there a maintenance plan for the roof, waterproofing and common areas?

Good developers welcome these questions. Vague answers are worth noting.

For a flat that is still under construction

A building's strength is decided during construction: the concrete mix, the placement of reinforcement, compaction, curing and how long the props stay in. Once the concrete is poured, much of this cannot be checked without testing. If you are buying off-plan or during construction:

• Visit the site, more than once, and at different stages.
• Look at the reinforcement of a floor before it is cast: are the bars tied, supported on spacers, with closely spaced ties near the ends of columns?
• Ask whether concrete samples are taken at each casting and tested at 28 days, and ask to see the results. See concrete quality control on site.
• Note whether new floors are cured with water for the first week, and how soon the props underneath are removed.
• Ask which brand and grade of reinforcing bar is used, and whether mill certificates are kept. See rebar grades.

Red flags that should pause a purchase

None of these automatically rules a building out, but each one is a reason to stop and get an engineer's opinion before paying:

• More floors standing than the approved plan allows, or a rooftop floor "to be regularised later".
• No structural drawings, and nobody can name the structural engineer.
• Columns on the parking floor that are visibly smaller than those above, or columns that start on beams.
• Diagonal cracks in walls, cracks in columns or beams, or rust stains and spalling under bathrooms.
• Fresh plaster patches on columns or beams in an otherwise older finish.
• A drooping balcony, or ponding water on the roof.
• Walls removed or openings cut between flats or shops.
• Signs of settlement: sloping floors, doors that jam on one side, a gap at the plinth.

Second-hand flats: ask about the building's history

For an older flat, the building's history matters as much as its design. Ask the owners' association whether the building has had any structural repairs, roof or waterproofing work, problems after earthquakes or floods, or changes such as added floors or a converted ground floor. Ask when the roof was last waterproofed and whether there is a record of maintenance. A building that has been cared for, with records, is usually a safer purchase than a newer one that has not.

Step 4: When to bring a structural engineer

For many buyers, the checks above are enough to choose between buildings. Bring an engineer when:

• The building has no structural drawings, or its designer and supervisor are unknown.
• Floors appear to have been added, or the use has changed.
• You see structural cracks, rust stains, spalling or sagging.
• The building is older than BNBC 2020 and has an open ground floor.
• You are buying several flats, a whole floor, or a commercial space where the load matters.

A pre-purchase structural inspection typically includes a review of the documents, a walk-through of the structure, a crack and condition survey, and, where useful, non-destructive tests on key columns and beams: rebound hammer readings for concrete uniformity and a cover meter or scanner to check the bars and ties. You receive a short report in plain language. The cost is a small fraction of a flat's price.

The bottom line

Before buying a flat, check the building as carefully as the flat. Ask for the approved plan, the structural drawings and the soil report, and compare the approved floors with what stands. Look at the ground floor, columns, cracks, damp, balconies and the roof. Ask who designed and supervised the building and to which code. And when documents are missing, floors have been added or the structure shows distress, ask a structural engineer to inspect before you sign. It is a small cost against the largest purchase most families make.