Renovate or Build New? How to Decide What to Do With an Old Building

Renovate if the structure is sound, the layout can be adapted to your needs, and the renovation cost is well below the cost of a new building, usually less than about 50 to 60 percent of it. Rebuild if the structure is failing, the layout cannot work without major changes, the building cannot take the extra floors or services you need, or the renovation would cost nearly as much as new. The deciding step is a condition survey by an engineer before you commit either way, because the answer depends on what is inside the walls.

Start with a condition survey

A structural engineer, ideally with an architect and a quantity surveyor, should inspect:

• Foundations: signs of settlement, cracks that run through floors and walls.
• Frame: concrete spalling, rusting reinforcement, sagging beams or slabs.
• Walls: cracks, damp, and the quality of blockwork and plaster.
• Roof: trusses, sheets, slab waterproofing.
• Services: age and condition of wiring, plumbing and drainage.
• Hazards: old asbestos sheets, which need careful removal by specialists.

Testing may include concrete cores or rebound hammer tests. See signs a building needs a structural inspection.

When renovating makes sense

• The structure is sound or needs only local repairs.
• The building is in a good location you cannot replace.
• The layout works with moderate changes.
• You need to keep using part of the building during works.
• The building has heritage or character value, as in old town areas like Zanzibar's Stone Town.
• Permits for a new building would be hard to get, or would require a smaller footprint under current rules.

When rebuilding makes sense

• The structure has serious problems: major settlement, heavy corrosion of reinforcement, or poor original construction.
• You need more floors and the foundations cannot carry them.
• The layout fights the new use, for example turning many small rooms into an open office.
• Every service (wiring, plumbing, drainage) needs replacing anyway.
• Renovation estimates keep growing as more problems are found.

Compare the costs honestly

Renovation carries more unknowns, so use a larger contingency. Our renovation cost guide and office and shop renovation checklist give more detail.

Think about disruption and phasing

If staff, pupils or customers must keep using the building, renovation in phases may be the only option. It takes longer and costs more per square metre, but avoids moving out. See renovating a school or office while it stays open.

Permits and rules

Both renovation and new building may need a permit, especially when the structure, use or footprint changes. A new building must meet current planning rules, which may limit height, setbacks or parking in ways the old building did not. Check this early, because it can make renovation the better option. See our building permit guide.

Middle options

The choice is not always all or nothing:

• Strengthen and extend: keep the structure, strengthen it, and add a new wing. See extending a building.
• Keep the shell, replace the inside: a full internal refit with new services.
• Phased replacement: demolish and rebuild one block at a time on a large site.

A simple decision checklist

1. Is the structure sound, according to an engineer? If no, lean towards rebuild.
2. Can the layout meet your needs with moderate changes? If no, lean towards rebuild.
3. Is renovation below about 60 percent of new build cost, after contingency? If no, lean towards rebuild.
4. Must the building stay in use? If yes, lean towards renovation or phasing.
5. Do current rules limit a new building more than the old one? If yes, lean towards renovation.

A worked example

Take a single-storey office block built in the 1980s, about 400 m², that an organisation wants to turn into a modern office for 50 staff.

• The engineer finds the foundations sound, but the roof trusses have termite damage and the wiring and plumbing are original.
• The layout is a long corridor with small rooms. Some walls are load-bearing.
• The QS estimates a full renovation (new roof, new services, new finishes, some wall changes) at about 55 percent of the cost of an equivalent new building.

The building would also need a second floor within ten years, but the engineer says the foundations cannot take one. In that case the client may still choose to renovate for now, accepting that a new block will be built elsewhere on the site later, or may decide that a new two-storey building is the better long-term answer. The numbers alone do not decide it. The plans for the next 10 to 20 years do.

Questions to ask your engineer

1. What is the remaining life of the structure if we renovate?
2. Can it take extra loads or floors?
3. What hidden problems might we find once we open walls and ceilings?
4. How much contingency would you advise?
5. Which repairs are urgent and which can wait?

Frequently asked questions

How long does a building last in Tanzania?

A well-built reinforced concrete building can last 50 to 100 years with maintenance. Poor concrete, coastal salt and neglect shorten that a lot.

Is renovation always cheaper than rebuilding?

No. Once structure and services all need major work, renovation can approach or exceed the cost of new.

Can an old single-storey building take another floor?

Only if an engineer confirms the foundations and columns can carry it, which is often not the case for buildings not designed for it.

What is a condition survey?

An inspection of the structure, fabric and services by qualified professionals, with a report on defects, repairs and costs.

Not sure whether to renovate or rebuild?

Vika Construction renovates bank branches and offices and builds new ones. See our renovation and fit-out work or contact us to arrange an assessment.