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Despite the corona crisis: There is a construction boom in Germany and thousands are fulfilling their dream of having their own four walls.

In the low-interest phase, your own property offers the best protection for your savings and at the same time enables you to build up a private pension plan.

The Baukindergeld is also increasingly being invested in the new building.

In order for the expensive investment to pay off in the end, it is also important that the building is built without errors.

But unfortunately construction defects are happening more and more often, complain building experts.

This is due to increasingly complex technology.

And not infrequently because of a lack of knowledge.

The working group for contemporary construction eV (Arge) has analyzed the execution quality on the construction sites in Germany together with the Association of Private Builders (VPB).

The basis is formed by 1265 test reports from building experts for single-family houses between 2017 and March 2019.

Even with normal walls there are problems

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The bitter balance: A flawlessly built house seems to be the big exception.

A third of all plumbing work, a third of all heating installations, a good quarter of all electrical installations, but only ten percent of the installed ventilation systems were faulty.

In the shell, there were problems with the walls in 32 percent of the cases - be it that the dimensions were not adhered to, the wrong building materials were used or the insulation was incorrect.

Sometimes that's just a visual flaw, sometimes a lack of insulation means that moisture can penetrate the wall.

This then causes damage that can cost tens of thousands of euros to repair.

Moisture is the biggest problem in new buildings.

According to a study by Arge and VPB, it affects 48 percent of all error messages on soles and ceilings and their superstructures.

Thermal bridges, cracks in the masonry or screed, faulty sound insulation or problems with the energy standard are further sources of error that affect between twelve and 21 percent of new buildings.

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Moisture that cannot dry off leads to mold.

According to the study, this occurs most frequently in the solid wall area.

There is also mold growth in the roof, but that cannot be properly assessed on many construction sites because mold is easier to see on the wall in the shell than in the roof structure.

Mostly it is about mold during the construction phase.

The water problem with flat roofs

"This can be, for example, mold on the rafters that can be caused by the open in-ground stairs," the report says. This happens especially when moisture from fresh screed and plaster condenses in the roof structure. If ventilation is not provided, mold is the consequence. And up to a roof pitch of around 20 degrees, every fifth roof is affected by penetrating moisture. With stronger slopes it is only five percent. “The flatter a roof is, the more error-prone it is,” according to the study.

Errors occur when installing windows in 64 percent of all cases.

“With regard to the installation, it can be seen from the experts' comments that there is predominantly no fastening according to the RAL installation guidelines for windows and house doors.

In several cases, the lower end is only made with construction foam, and in many cases there is no sloping foil installed under the windows and doors, ”the authors of the study write.

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Incidentally, the low damage rate in the ventilation systems is no reason to give the all-clear.

"Experience has shown that the actual error rate in ventilation systems is higher, since most problems only occur after commissioning."

When installing the heating system, errors were reported in only 22 percent of the houses tested.

Half of them had incorrectly insulated pipes.

Incorrect regulation or coordination, incorrect dimensioning of the heating, problems with the solar system or leaks were less common.

Errors are discovered too late

In the building damage report by VPB and Arge, the experts named damage of up to 5000 euros per house for 58 percent of the cases examined.

For almost 40 percent, the cost of troubleshooting ranged between 5,000 and 50,000 euros.

In seven percent of the cases, the damage exceeded a value of 50,000 euros.

"The consequential costs of errors would certainly be higher if the deficiencies had not been recognized by the experts in good time," says the report.

Because structural damage becomes more expensive if it is repaired later.

The Bauherren-Schutzbund (BSB) has calculated the costs building owners can save if they take care of the elimination at an early stage.

A wrong connection in the roof structure can be fixed in the shell construction phase for 6,000 euros.

But if that only happens on the finished house, it will cost 40,000 euros.

A lack of sealing in the threshold area of ​​floor-to-ceiling windows causes structural damage of 22,000 euros - the error of removal in the construction phase costs only 1,400 euros.

It would be just as expensive to pull in a vapor barrier during the shell construction.

But it would cost 31,000 euros if the damage is to be repaired later.

"If the following trades are based on poorly executed areas, errors can be recognized with difficulty or only with great effort," says BSB managing director Florian Becker. A BSB study based on 700 site inspections in 100 new building projects by the end of 2019 revealed an average of 29 defects per house construction. Today, building without defects can be ruled out, the requirements are too complex and the market too overloaded, says Becker.

The VPB sees it similarly: "The complex interaction of different companies and people often leads to defects in buildings," the report says.

The sophisticated technology of the legally required high-efficiency buildings poses constant new challenges for everyone involved in the construction.

In many cases there is still a lack of implementation.

Not every construction error leads to serious damage, but construction errors are important indicators of execution problems and weaknesses in components and in constructions.

There is often a lack of professional construction supervision

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"It is important that errors are detected early, for example with the help of professional construction supervision," demands Becker. But that rarely happens. "More than 90 percent of all privately purchased apartments and single-family houses are built turnkey," says VPB Managing Director Corinna Merzyn. A freelance architect who could advise clients as an independent trustee is not involved. Everything is planned, built and checked by a supplier company.

"Even the building authorities or the financing banks usually do not carry out any checks with regard to the planning and construction quality." In this situation, the independent commissioning of an independent, construction-accompanying quality control is the only option for building owners, neutral, expert decisions for the most expensive To get investment projects of a lifetime.

In 1996 the federal government published its last building damage report.

Since then, there are no more reliable figures on damage to the building.

With their building damage report, Arge and VPB wanted to show the planners, all those carrying out the work and also the building owners themselves where there is a problem, where it is worthwhile to take a closer look at planning and construction or to reconsider one or the other detail.

"Secondly, this study is also aimed at the legislature and is intended to arouse understanding in politics that not every technical request, every requirement and every regulation can be easily implemented in practice," says Arge managing director Dietmar Walberg .

“The report is also informative from an economic point of view,” says Merzyn.

“It documents the considerable destruction of assets that can be traced back to incorrectly manufactured building details.

What is particularly annoying is that the repairs and duplication of work that are then necessary are unnecessarily paralyzed by the construction capacities currently urgently required for residential construction. ”However, this circumstance has so far only been little discussed and has increased with the low detection and complaint rate for construction defects in the private home sector to do.

Where builders have to look closely

For this reason, too, another unreported number of construction defects in turnkey residential buildings can be expected, according to Merzyn.

Not every construction error leads to serious damage, but construction errors are important indicators of execution problems and weaknesses in components and in constructions.

This would show where technical clarification and further training in the construction industry make sense.

According to Merzyn, they would also show at which points construction projects should be reconsidered in terms of planning because they are prone to errors - and at which points consumers should look particularly carefully when they are building from scratch.

"Through the analyzes we can identify tendencies and hopefully contribute to a decrease in construction errors in the future and some fault-prone constructions to be reconsidered."

It is more likely, however, that builders will get into trouble with botch and mistakes.

Therefore, it depends on a correctly carried out acceptance, which is at the end of every construction project, according to the residential property association.

Because if a visible defect is overlooked during the building inspection, the builder loses the right to rework or retention.

It makes sense to consult an expert or architect for the acceptance.

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When the building is accepted, a comprehensive protocol should be drawn up that records any defects.

However, insignificant defects are no reason to refuse acceptance, according to the association.

Defects that only appear or become recognizable after acceptance can be asserted within the statutory warranty period.

In the case of private house construction, according to the BGB, it is usually five years from acceptance.

If damage occurs during this time that was caused by incorrect assembly or materials, the responsible building contractor, craftsman, supplier or, if necessary, manufacturer must repair the damage at their own expense.

The causes lie before the start of construction

However, if a warranty period in accordance with Part B of the Contractual Procurement and Contracting Regulations for Construction Services (VOB) has been agreed in the contract, shorter periods may apply - four years for buildings and two years for craftsmen's services.

"The builder must check what applies in his case - possibly with the help of a specialist," says the home ownership association.

"The causes of the errors often lie before the start of construction," says BSB managing director Becker.

"Often, important planning documents are missing, without which implementation in accordance with the order is hardly possible." Becker advises control: "Builders should have their documents checked for completeness by an independent expert and, if necessary, submit additional requests to the company."

This article first appeared in April 2020.