Can a mechanical engineer build a house

Own contribution when building a house: This is how much you can save

By doing your own thing, the costs of building a house can be reduced significantly - they contain enormous savings potential. But it doesn't always make sense to lend a hand yourself. You can read here which work you should rather leave to a specialist and what you need to consider when working on your own.

Own contribution when building a house: This is how much you can save
Own contribution when building a house: This is how much you can save

Building a house yourself is a good way to save money, for example if you do not have enough equity to finance the house. But you cannot do every job yourself as a do-it-yourselfer. The risks are often too great and the necessary specialist knowledge too small. In addition, the time required can often go beyond the scope. So only take on activities that do not represent excessively high professional and technical requirements and that can be specifically distinguished from the contractual services of the house construction company or the property developer.

What is a muscle mortgage?

The muscle mortgage is understood to mean those costs that can be saved through manual work. In this way, you can not only reduce the loan amount, but also achieve more favorable interest rates for the bank's construction loan. As a rule, the bank recognizes around 15 percent of the total construction cost as own contribution. The building code stipulates how the monetary value of personal contribution is determined: "The value of self-help is to be recognized as personal contribution with the amount that is saved compared to the usual costs of entrepreneurial performance (§ 36 Paragraph 3 II WoBauGe)."

Herbert Groth, Head of Sales for Construction Financing and Real Estate at Frankfurter Sparkasse, explains: “In an initial discussion, the client and LBS or savings bank adviser clarify the basic features of the financing. You determine the total costs, the loan amount and the equity. Personal grabbing replaces part of the equity. The amount depends on which trades the customer wants to do himself and what technical skills he has. Then the personal contribution is broken down into wage and material costs. The value of one's own contribution is only measured according to the saved wage costs. "

These experts will be happy to help you:

Realistically assess personal performance

"Those who build themselves need the necessary know-how and a lot of time," warns Bernhard Riedl, consultant in the Association of Private Builders (VPB). Homeowners must ensure that the construction site runs smoothly and control the work. Additional personal contributions can quickly become overwhelming. If you take over, you risk botch-ups and delays and, ultimately, that reworks make the construction more expensive. "The future owner should limit their own contribution to a maximum of five to ten percent of the total costs," recommends Florian Becker, managing director of the Bauherren-Schutzbund (BSB). It should also be taken into account that do-it-yourselfers often buy tiles or paints more expensively than a building contractor who benefits from volume discounts. Often the right tool has to be purchased first. In addition, laypeople lack routine. Experience has shown that they can handle a maximum of two thirds of the performance of a professional. Builders should ask themselves critically whether the effort is even worth it.

Make arrangements and calculate correctly

If you still want to tackle it yourself, you should definitely contractually regulate your own contribution. Then it is clear which work the contractor will take on and which will not. And the customer knows how much they are saving on costs. In order to avoid delays, in-house work must be precisely integrated into the construction process. This applies in particular if the client is building with a general contractor or property developer. "The contractual partners should precisely define the interfaces between external and in-house work, both in terms of organization and time and technology," advises Bernhard Riedl. This is the only way to avoid performance gaps. If the builder cannot complete his work within the agreed period, he may have to commission external companies. Refinancing may then even be necessary. In addition, the client should make a comparative calculation: Anyone who takes extra unpaid vacation, for example, should carefully weigh up whether their work compensates for the lost wages.

Do not forget to clarify who is liable for what if damage is caused by personal contribution and delays occur. "It is best to get advice from building experts in advance," says Riedl.

With regard to the calculation, you should have your construction company give you a list of the material and wage costs for the desired personal work before concluding the contract. So that the contractual completion date can be met, fit your work into the schedule and coordinate it with the architect, the house construction company or the property developer.

Personal contribution also harbors risks

Not all work is suitable for the client. Trades such as heating, electrical, gas and water installation belong in the hands of specialist companies. Laypeople should be particularly careful if possible errors have far-reaching consequences for the entire construction. Then there can also be a dispute about who caused the defect: the client or the construction company. In principle, there is no guarantee for personal contributions. "Builders are on the safe side if they only take on work that only occurs once the actual house has been built and the house has been approved," says Florian Becker. Above all, you can trust yourself to do the finishing work and design the outdoor facilities. According to the building owners' protection association, those trades are to be preferred that contain a high proportion of wages and a low proportion of materials.

Secure helpers

Without the support of friends, it is hardly possible to build a house yourself. So that the statutory accident insurance also takes effect on the private construction site, the building owner must register all private helpers with the BG Bau trade association no later than one week after the start of construction. Even if they work free of charge or the client is already insured. Otherwise he risks a fine of up to 2,500 euros.

What you can trust yourself in each case

Not everything belongs in the hands of laypeople. So don't overestimate your abilities, but rather weigh them carefully what you can do yourself. The following classification can help you:

Painting and wallpapering work: They take a long time (around 125 hours), but with a little patience and the right equipment, you can save between 60 and 80 percent.

Lay tiles: It is true that the costs here mainly depend on the quality of the selected tiles. However, if a craftsman is also commissioned, around 30 euros per square meter are incurred.

Laying laminate flooring: You can expect 15 to 20 euros per square meter and a time investment of around 90 hours. For installation by a craftsman, you have to calculate 30 to 40 euros per square meter.

Drywall: In drywall construction, Rigips panels must be laid, filled and sanded. This work is extremely time-consuming (about 102 hours), but can save between 60 and 70 percent in money.

Outdoor facilities: Depending on your wishes, you can get by with little money here.

Structural work: These take up a lot of time and are accordingly wage-intensive. Almost half of the construction costs can be attributed to the shell, of which around 40 percent are material costs. Even if you probably can't do everything yourself, just helping yourself can save you money.

Windows, doors and stairs: In contrast to shell construction work, the wage share is very low here, so that only around 10 to 30 percent of the total costs can be saved.

Plaster: Plastering walls is also time-consuming, but it is worthwhile if you consider the savings potential of 70 percent.

Sanitary installation: The basic rule here is: it is better to skip your fingers, unless you are a specialist and know exactly what to do.

Electrical installation: The electrical installations should on no account be tackled by laypeople, because the risk of electrical accidents is high. Better leave the work to a professional.

That brings you your own contribution

Using the following tables, you can see how much potential savings can be made when building a house. The data refer to an end-row house with a cellar with three floors and 140 square meters of living space. Overall, the client saved around EUR 18,867 of EUR 253,482.

Type of personal contribution

Expenditure of time


Dry construction with thermal insulation of the roof surfaces

102 hours

4.085 €

Put window sills inside

3 hours.

124 €

Lay tiles and slabs

48 hours

1.919 €

Set room doors

79 h

3.173 €

Painting and varnishing work

94 hours

3.775 €

Install floor coverings

89 hours

3.553 €


31 hours

1.238 €

Outdoor area

30 hours

1.000 €

Total own work

476 h

18.867 €

Source: Association of Private Builders - Regional Office Munich and the surrounding area

Guarantee for own work

The construction company does not assume any guarantee for personal contribution or consequential damage connected with it. You cannot assert any recourse claims against your construction workers either. In order to secure warranty claims against the company, one must carefully formulate in the contract where the performance of the professionals ends and your own begins. You are on the safe side if you thoroughly check the company's preparatory work for defects and, if in doubt, request rectification. Only after the acceptance do you start your project. Conversely, you can also have your sub-plant approved by the site manager before the next specialist begins his work.

Interview: Those who do the work themselves save money

The architect Marai Ströcker and her husband worked hard to build their own house - and they did so with a system. In an interview with DAS HAUS, the client from the Soest district reveals how personal work is successful.

A survey of building owners recently showed that almost 90 percent of building owners are working on the construction site. You and your husband have also done a lot of their own. Was it worth the effort?

In any case. We saved a total of 100,000 euros - a good third of the construction costs per square meter. Without our own contribution, we would not have been able to afford a house of this size.

As an architect, you are a specialist. Surely that was a big advantage?

Correct. I was able to do all of the planning myself. Personal performance also always depends on the craftsmanship. Fortunately, my husband is very gifted in this regard. Single-handedly, he handled almost the entire interior work, the complete electrical installation and the attachment of the wooden facade. By the way, he is a mechanical engineer by profession - so he has nothing to do with construction.

From your experience as an architect: How much can average builders save with their own contribution?

Ten percent of the total costs are possible. For those who can handle tools well, a lot of work can be done without specialist knowledge. But then you should have a specialist on hand for every trade. Watching a video on YouTube is by no means sufficient for building a house.

Where can you find a specialist if you don't have a craftsman in your family or among friends?

Do not buy the material from a hardware store, but from a specialist store. You pay a little more, but receive good goods and, above all, a competent contact person. Builders can then immediately ask whether they can contact us again in the event of problems. Specialty shops also often lend out special tools, and the expert usually shows how to use them correctly.

You have planned your own work from the start. How does it work?

The choice of materials is important. A wooden house offers the greatest opportunities to collaborate. Whoever builds a solid house must be able to build walls. Screwing panels to the wall, on the other hand, does not require any special skills. After all, everyone has already had a cordless screwdriver in their hand. Among other things, we have a wooden facade instead of plaster and wooden floors instead of stone. Which work you can do yourself depends of course on your own abilities. Tiles are not our forte, so we've kept them to a minimum. It is also more difficult with complex architecture - for example with a gallery, open stairs, frameless glass railings or round walls.

Which jobs are worth doing yourself?

Craftsmen usually buy building materials much cheaper than building owners. For this reason, trades with high labor costs and low material costs are suitable for personal work. This applies to drywall, for example. Attaching lightweight walls, leveling them and sanding them is very time-consuming, even for a specialist. The layman can do this more cheaply. And you can't do too much wrong either. Painting work, floor coverings and outdoor facilities such as splash protection for the house, paving work, laying terrace slabs or building garden walls are also easy to perform.

Which activities should laypeople better leave to a specialist?

The statics and all trades where defects can have serious consequences. Caution is required with water and electrical installations as well as with roof and floor coverings. If the floor tiles in the shower are not tight, you will quickly have moisture in the screed and high repair costs. There is no guarantee for anything you do yourself. You can still help with difficult trades, but better only under the guidance of a craftsman.

Craftsmen and builders work together?

Yes, the client then becomes a helper. Tradespeople often bring a colleague with them because some work is better done in pairs - even if it is only a matter of an assistant handing over material. Builders save the hourly wage of the second man if they assist themselves instead. The prerequisite is, of course, that the craft company gets involved in this deal.

Which mistakes should one absolutely avoid?

Wrong self-assessment is worst. Builders who have little experience with their own work often overestimate their skills and the time required too little. This is risky, and not just because of possible shortcomings. If you block a specialist because your own trade was not finished on time, you cause high additional costs.

What should builders consider in their time planning?

A layman always needs significantly longer to work than a professional. It is best to concentrate on a maximum of two or three trades that do not follow one another. This creates a breather. In general, breaks are very important, because building a house is exhausting. At first we went to the construction site every evening and every weekend. It was a tough time. Later we only planned the weekends for work, and things went a lot better. The days of the week served as a buffer: if something had to be finished quickly, we exceptionally screwed things up after work.

Many build because they need more space for the growing family. How do you build a house with a child?

When we built our house, our son was three years old. He was mostly with us on the construction site, but was easy to keep busy. Sometimes he was allowed to turn screws into a piece of wood, sometimes swing the brush. Of course, I always kept an eye on him. That limited my workforce, but I was still able to help. We now have two children. Personal contribution to the extent that we have done would no longer be conceivable today. Our working hours would easily double.