When a villa runs over budget, we usually look for the culprit on site: the contractor, material prices, delays. But experience across residential projects in Babol and Babolsar points somewhere else. A large share of the extra cost was decided at the drawing table, months before the first excavator touched the ground.
Architecture has a name for this: the cost–influence curve, formalised by Patrick MacLeamy in 2004. Its logic is simple and unforgiving — as a project advances, your ability to affect the outcome falls while the cost of every change rises. A change that is one line during concept design becomes a demolition after the concrete is poured.
Below are seven mistakes we have seen repeatedly in northern Iran's residential projects, and the precise mechanism by which each one consumes your budget.
1. Starting design without a soil investigation
This is the most expensive saving available. To avoid the relatively small cost of soil testing, the client effectively hands structural design over to guesswork. The result is one of two outcomes, and both are costly:
- An over-conservative foundation: without reliable data, the structural engineer must adopt a large safety margin. That means concrete and reinforcement that were never needed get bought and placed. Construction management research identifies inadequate geotechnical investigation as a leading source of over-designed foundations and cost overruns.
- An inadequate foundation: the more dangerous case — differential settlement, structural cracking, and in the worst case retrofitting after completion, one of the most expensive engineering operations there is.
In the northern climate this matters more: a high water table and soft alluvial and clay soils behave in ways you cannot design a foundation for without proper knowledge. This is why we run internal training in soil mechanics and foundation engineering with Dr. Ghaseminejad — a foundation is not a decision to make on intuition.
2. A plan broken up for no reason
Geometric complexity is not a mistake in itself; unjustified complexity is. Research shows the perimeter-to-floor-area ratio directly affects unit construction cost. Every additional break in the plan means:
- more foundation and wall length for the same usable area
- more complex, slower formwork
- more material waste, because standard materials — brick, panels, joists — must be cut to non-standard dimensions
- more construction details at junctions, and every detail is an opportunity for error
The distinction matters. At Villa 425 in Khazarshahr we deliberately elongated the plan east–west. That was not a formal gesture: the goal was to increase the building's exposure to the airflow running from shore to forest, creating suction and pressure zones for natural ventilation. The form came out of a climatic need. That is a world apart from a break introduced merely to look different.
3. Changing drawings after construction begins
This is the most frequent cost driver, and the worst part is that it was entirely preventable. Research published in the Civil Engineering Journal identifies design changes as a predominant factor in cost overruns, estimating they can add between 5 and 40 percent to project cost.
The mechanism is simple: moving a wall on a drawing costs an hour of the designer's time. The same move after the frame is built involves demolition, discarding purchased materials, halting other trades, and usually a chain reaction through services and finishes.
The answer is to bring decisions forward, not to speed up execution. That is why we hold a project review session before site work starts — the place where conflicts are meant to be resolved on paper, not on site.
4. Ignoring building services during design
In many residential projects the architectural drawings and the mechanical and electrical drawings are produced separately, without coordination. The conflicts surface later on site: a duct routed where a structural beam sits, drainage clashing with the foundation, insufficient ceiling void for services to pass.
The cost of resolving a clash is an exponential function of when it is found. The same conflict that takes a few hours in a design coordination meeting becomes days of work, demolition, and several trades standing idle once ductwork is already installed.
5. Ignoring climate — moving cost into operation
This mistake shifts cost from the construction phase into the entire life of the building. A villa designed without regard for wind direction, solar exposure, and humidity may not cost more to build — but it will spend the rest of its life using expensive mechanical systems to do what good design would have done for free.
The vernacular architecture of the Caspian shore understood this for centuries. Academic studies of traditional Mazandaran houses show the porch was not merely decorative; it functioned as a ventilation system, using wind energy to condition the house. In humid climates, natural ventilation is the most effective cooling strategy available.
At Khorshid House we designed the ratio of glazed surface to façade so that no rigid wall appears to exist. That decision built the quality of the space and reduced daytime dependence on artificial lighting.
6. Choosing materials without accounting for humidity and coastal salt
In Babolsar, Khazarshahr and along the shoreline, a building faces a combination of high humidity and chloride ions carried in sea air. That combination triggers a well-documented decay mechanism: chlorides gradually penetrate the concrete, reach the reinforcement, corrosion begins, the corrosion products occupy more volume than the original steel, internal pressure builds, and the concrete cracks and spalls from within. Constant moisture accelerates the cycle.
Here is the economic point: the preventive measures — greater concrete cover over reinforcement, a mix design suited to a marine environment, correct waterproofing details — cost very little at the design stage. Repairing a corroded structure years later is among the most expensive work possible.
7. Treating floor area as the measure of value
The most common misconception is that a better villa means a bigger villa. But every additional square metre multiplies its cost through every layer: foundation, frame, envelope, finishes, services — and then, permanently, heating, cooling and maintenance.
Khaneh Yar in Bandpey, Babol, at 180 m², is one of our smallest projects. The real work there was correcting the building's proportions and making a space where children build memories and a mother finds calm. Its value did not come from its size.
Before fixing the area, ask: does this extra metre improve the quality of living, or only the number on the deed?
What these seven have in common
Look again at the list: not one of them is an execution error. Every one is a decision made — or not made — during design. This is exactly what the cost–influence curve says: the most expensive moment to correct a decision is the latest one.
Investing in the design stage — soil investigation, services coordination, climate analysis, finalising drawings before work starts — looks like an expense at first. It is in fact the only phase of the project where you can achieve the greatest effect at the lowest cost.
If you are about to begin a residential project in Babol, Babolsar or along the Mazandaran coast and would like to discuss your site or your idea, you can get in touch or look through Charsou's completed projects.
