Buying a new-build in Croatia? These are the details you should check first

(Photo: DOMinvest grupa)

We have all seen new-build homes that develop dark damp patches after just a few years, while residents are forced to install additional sound insulation to block out their neighbours. But where do problems in new residential buildings most often begin?

To find out which elements developers are most likely to cut costs on, and how those decisions can directly affect the durability, quality and comfort of a building, we spoke to Croatian construction expert Saša Perko.

“Developers usually do not save money on what buyers can see, but on what lies beneath the finishing layers. Most often, this includes reinforcement, waterproofing, connection details, thermal bridge breaks at balcony slabs, sound insulation elements and, quite often, all the consequences of insufficiently detailed design work,” Perko said.

“Taken together, these items rarely account for more than a few per cent of the investment, but they determine whether a building will have damp and black patches five years later. The problem is usually not negligence, but the fact that pressure on deadlines and costs is dealt with precisely where the consequences will not be immediately visible.

“The buyer gets an apparently finished and tidy apartment, while the bill arrives several years later through maintenance charges and repairs.”

Sound insulation: what is behind the wall matters

Hearing every footstep or conversation from a neighbouring apartment is a common problem in multi-residential buildings.

Perko explained what materials, wall thicknesses and floating floors are needed to achieve high levels of sound insulation.

(Photo: DOMinvest grupa)

“Sound insulation is better when the material is denser, which is why reinforced concrete walls should always be used between apartments. We then add a layer of mineral wool with plasterboard lining, providing both thermal and sound insulation,” he said.

“This is particularly important where one apartment is occupied every day while the neighbouring property has been bought as an investment and is only occasionally used – or never used.

“For impact noise, such as the sound of someone walking above you in high heels, a floating floor is required: 2cm of EPS beneath the screed and, importantly, perimeter expansion strips along all walls.

“Without these strips, the screed touches the wall and transfers impact noise into it, which can then travel into neighbouring apartments.”

Why some new-build facades develop black patches

After just a few seasons, the facades of some new buildings can begin to look worn, with algae and fungi creating dark patches.

Perko said this is usually linked to a combination of factors.

“It is almost always a combination of insufficient vapour permeability in the system and a poor choice of finishing layer. Particularly on northern facades, moisture can remain in the finishing layer, and that is all algae and fungi need,” he explained.

As for the insulation system his company uses, Perko said they favour mineral wool rather than EPS insulation.

(Photo: DOMinvest grupa)

“We always install mineral wool on our buildings, never just EPS, because mineral wool is non-combustible and vapour-permeable,” he said.

“There is also a practice of combining EPS with fire-resistant mineral wool bands every two floors, but we do not use that approach. Mineral wool has one disadvantage, it is more difficult to install, meaning that under certain sunlight angles the facade can appear slightly wavy.

“That is an aesthetic compromise we are happy to accept in exchange for a non-combustible, vapour-permeable facade with better energy performance than EPS.”

Flat roofs: are they really more likely to leak?

Flat roofs have become increasingly common in modern residential construction, but concerns about leaks remain among buyers.

Perko said those concerns are partly rooted in older construction methods.

“The fear of flat roofs comes from the days when bituminous felt was used. It was not UV-resistant, so after several seasons it would dry out and crack,” he said.

“Today, it is neither the same product nor the same technology.

“We use flat roofs exclusively, with a TPO membrane as the main waterproofing layer and two layers of bituminous membranes as secondary protection. With this type of waterproofing, water simply cannot ‘break through’.”

He added that every roof should undergo a watertightness test before the layers above it are closed.

“After that point, repairs become several times more expensive, in money, energy and stress,” he said.

“A roof does not leak because it is flat. It leaks because of poor detailing, inadequate falls and poorly executed penetrations. A pitched roof is therefore not necessarily the safer choice; it is simply a solution with fewer critical details.

“If a flat roof is properly constructed, it is a much better solution.”

Windows, balconies and thermal bridges

Poorly installed windows and inadequately designed details around balconies and openings can create thermal bridges and condensation.

Perko said the critical issue is not the glass itself but the connection between the window and the building.

(Photo: DOMinvest grupa)

“A window leaks at the connection, not through the glass. That is why RAL installation is essential, with the joint sealed at three levels,” he explained.

“This means a vapour-tight tape on the inside to prevent moisture from the apartment entering the joint, a vapour-permeable tape on the outside so that any moisture that does enter can escape, and thermal insulation between the two.

“Installing a window using only polyurethane foam looks just as good initially, but after two winters you can end up with condensation and mould around the frame.”

The choice of profile depends on the building, location and budget, he said, with PVC and aluminium both having their place.

“But triple glazing and RAL installation are the standard without exception,” he said.

“The balcony slab must also have a thermal bridge break. Otherwise, cold concrete extends into the heated part of the building and creates a permanent cold spot indoors where moisture accumulates.”

What should buyers ask a developer for?

When viewing a completed apartment or buying into a building under construction, buyers need to know which technical details and documents they should request.

Perko advises buyers to focus on things they cannot see.

“Ask for what is invisible but must exist on paper,” he said.

“First, ask for photographic documentation of concealed works – photographs of waterproofing details, penetrations and connections before they are covered by finishing layers.

“This should be done systematically, not just for the buyer but for the developer themselves. If a problem ever occurs, we immediately know where to look, making repairs targeted rather than having to demolish half the apartment.

“Second, ask for warranty certificates for all mechanical and electrical installations, as well as proof that the roof has undergone a watertightness test and that pressure testing of the water installations has been carried out.

“Third, ask for a building maintenance manual explaining what needs to be maintained, how and how often. Without this, a building can become expensive within its first few years.”

The real cost of cutting corners

Buyers often focus on the price per square metre, but poor insulation, waterproofing and roofing can have a major impact on maintenance costs and building reserve funds over the first five to 10 years.

“If a building has been properly constructed, there should not be any extraordinary costs during the first ten years, only regular maintenance of common areas and the individual apartment,” Perko said.

“There is a common misconception that someone else will replace the silicone around your bathtub or repair a socket that the owner has pulled out of the wall through improper use.

“Two things can nevertheless occur regularly and are not a reason for panic. Following subsequent settlement of the ground, micro-cracks can appear in plasterboard walls and at their connections with concrete. This is basic repair work.

“Another is calibration of heating and cooling systems, which should be monitored during the first few seasons because it has a direct impact on energy bills.

“The real difference emerges when insulation, waterproofing or roofing have been poorly executed. Then we are no longer talking about maintenance but repairs costing tens of thousands of euros, which residents ultimately pay through the building reserve fund.”

Design, materials or workmanship?

Asked whether the biggest problems lie in poor design, low-quality materials or workmanship on site, Perko said materials are currently the least concerning factor.

“Materials are the smallest problem today. Everything is available on the market and certified,” he said.

“The problem is poorly developed detailed designs, which often do not even exist, and construction work carried out without genuine supervision.

“When a connection detail or anchoring detail has not been properly developed in the design, the decision is ultimately made by a tradesperson on site, without calculations and without anyone checking it afterwards.

“That is why professional supervision is crucial, but only if it is genuine.

“At our sites, our own team of supervising engineers visits according to the phase and complexity of the project, from weekly coordination meetings to daily inspections.

“As long as it is possible for a final report to be signed without anyone actually checking how critical details have been executed, quality remains a matter of an individual’s conscience rather than a matter of the system.”

Speaking about specific materials, insulation systems and roofing solutions, Perko, who is also director of DOMinvest, explained how construction is approached across the company’s projects.

“I have mentioned most of the technical solutions in my earlier answers, so I will not repeat them. They all come down to one thing: we do not save on layers that the buyer will never see,” he said.

“The biggest difference, however, can be seen in decisions made at the project level rather than on the construction site.

“Heating and cooling in our projects is always based on heat pumps with underfloor heating, while some developers still install boilers. As a result, heating costs for our residents are at least twice as low.

“We design projects around greener solutions and aim to place as many parking spaces as possible in garages rather than outdoors.

“Thermal bridge break elements are installed without exception. We pay more attention to waterproofing than to any other part of the construction process, while floor plans are designed so that every square metre is usable rather than creating large corridors and rooms that nobody actually uses.”

Saša Perko (Photo: Dejan Tatomir)

Perko also addressed a growing concern among buyers: developers relying heavily on the cheapest available subcontractors.

He said DOMinvest takes a different approach by bringing design, construction and project development together within the group.

“Within the group, DI plan handles design, DOMinvest construction and DOMinvest development project development,” he said.

“That does not mean we carry out every trade ourselves, but it means that we are responsible for each project and manage it from the first project line through to handing over the keys.

“The difference is that there is no situation where the designer blames the contractor, the contractor blames the designer and the buyer does not know who to turn to.

“I will be honest, today I am on construction sites less often than I would like because the development of the group and its projects takes me away from them. But within the group we have around 15 site engineers who do that job better than I would, and I have great confidence in them.”

Perko said the group currently has four new projects in preparation, comprising around 300 apartments, a smaller development of around 20 houses, and a medical-use office building of approximately 10,000 square metres gross floor area.