Adding floors - Structural stability questionable

Hello everyone,
my partner and I are currently considering what our future living situation should look like.
In this context, the idea came up whether an extension of my parents' house might be an affordable way to create sufficient living space. We then inquired at the building authority whether this would be possible. According to the building authority, a full additional floor is not permitted, but a knee wall extension is possible.
The house was originally planned as a bungalow but had to be built with a pitched roof for legal reasons.
Whether an extension is technically feasible and whether it is within a budget we can afford is something we would now like to have checked by an architect or construction company. What costs should we expect for such a cost estimate?

Since we are complete laypersons and have not yet dealt intensively with the topic, we would be very grateful for some tips.

Best regards, Lili

When commissioning an architect, these are the service phases 1+2 (basic evaluation + preliminary design) according to the HOAI (Fee Structure for Architects and Engineers) with 2+7 = 9% of the total fee. The architect’s fee is not freely negotiated but is bound to the HOAI.

The fee is calculated based on the so-called chargeable net construction costs (cost group 300+400 building + technical equipment), the fee zone, the renovation surcharge, incidental costs, and value-added tax. The more extensive the scope of work becomes, the higher the so-called incidental construction costs (incidental construction costs), which include, among other things, the architect’s fee. Other incidental construction costs are the fees for the structural engineer, possibly also the surveyor, etc. The incidental construction costs in renovation projects overall (not just for the architect) amount to about 18-22% of the gross construction costs.

The architect prepares, in consultation with you, a preliminary design (max. 3 variants incl.) and a cost estimate, with which you can enter into financing considerations or financing negotiations with the bank. The architect also clarifies all the building and planning law questions that are always associated with a construction project. The architect delivers a approval-capable preliminary design/planning within your budget.

Adding an additional floor is generally worthwhile if the existing structure has sufficient statics and a usable shell construction. Bungalows from the 50s/60s are usually quite suitable, although mostly built rather sparingly. If the bungalow is a prefabricated house, I would be more skeptical.

Good evening Lilli,

Whether an extension is technically possible and whether it is within a financially feasible range for us is something we would now like to have checked by an architect or construction company. What costs can one expect for such a cost estimate?

Will has already shown you the path that must be taken for individual contracting via an architect. I would like to recommend that you proceed somewhat differently.

Adding onto an existing property "can" have something in common with the famous Pandora’s box, but it can also be quite easy to handle. (Unfortunately, you don’t mention how large the bungalow is and what the potential gained space could look like). To check this, the old documents – if available – can be used; if not, a structural engineer must come out and look at the existing property. In my opinion, an expert – at least a carpenter – should also be involved who can assess the roof and its structure; if necessary, this structure along with the roof tiles can be reused. Hiring a structural engineer costs money; the carpenter will most likely come to the construction site for free as part of an offer.

Before you and your partner get deeply involved with a possible extension, you should consult a financer you trust and discuss your financial possibilities. Only when you know exactly what you can handle financially will you know whether the project – at least from a monetary perspective – can be tackled. Once a sum “x” is known, go to the architect or construction company (with verifiable references in renovation) and present your project. Ask for an offer based on the assumption that an extension is possible; additionally, have them provide figures in case the bungalow needs “some” structural reinforcement.

Only when you have a binding offer, even two (before the first meeting with the architect, clarify whether the initial consultation is free; otherwise, you have signed a contract if you, in good faith, say “go ahead”) or three, will you roughly know where the journey can lead. Know whether you can manage the construction project and be able to make a final decision.

In this context – if and when the construction project is taken on, go to a tax advisor/notary beforehand and clarify the legal situation for both of you; you are not married.

Rhenish greetings

Thank you for the great advice. For a layperson, the flood of information on the WWW is somewhat confusing.

Precisely because of "Pandora's box," we are concerned about investing thousands of euros (more than 2500) in an architect/structural engineer only to find out later that the project exceeds our budget. According to your answers and my research, the service phases 1-2 should roughly be within our budget.

My grandfather designed and built the house in the early 70s. The living area is 140 sqm, and the house is partially basemented. The extension should therefore practically not exceed 105 sqm, although to my knowledge, sqm with sloping roofs are not fully counted, right? The building plan with structural engineering is still available. My father doubts that an extension is possible without additional reinforcement. The roof structure most likely cannot be reused.

We understand that it won’t be done with just a few tens of thousands of euros. But since land and property prices are very high here in the area and would significantly exceed our budget, we hope that it might be possible nonetheless. It is important to me, looking toward the future and possible need for help in old age, to stay close to our parents, hence our dilemma.

Regarding the financial framework, we have already considered a maximum limit for ourselves, which we want to state with a buffer of 50,000 euros for the planning.

Equity would then be around 15-25% depending on the actual final amount. The house in question is not currently burdened by any loan/mortgage.

The next steps now are, if I understood correctly, to coordinate the financing with parents and bank and then to go to the structural engineer or architect with a concrete figure (making sure to pay attention to how the consultation is compensated).

This has really helped us a lot. Thank you!

Best regards, Lili

Hello Lili,

something you should also think about in advance is securing the required loan.

Usually, such security is provided by a land charge. As it reads so far, the existing building including the land belongs to your parents.

Therefore, the security would also have to be provided by the parents, unless you convert the house into two legally separated condominiums after the renovation and thus establish a WEG.

Even if the parents were willing to have the land charge registered, in my opinion, there are at least two risks:

1. If you, for whatever reason, can no longer service the financing and it comes to a foreclosure, not only would you lose your apartment, but also your parents. However, this risk could be limited by a lifelong right of residence (registered in the land register) for your parents in their apartment. However, such a right of residence also significantly reduces the loan value.

2. Legally speaking, you (meaning your partner and you) do not own anything at all in this constellation. Therefore, it must be at least considered that eventually the entire property can become subject to inheritance tax. Potential disputes within the family aside.

Therefore, my recommendation would definitely be the real division into two apartments and the establishment of a WEG.

Regards,

Dirk

Hello Lili,

I am adding to my contribution, also with regard to epi's suggestion: Building within existing structures is a different matter than new construction on a "greenfield" site. Such a construction project within existing buildings always involves a as detailed as possible building survey, examining the condition of preservation and the usability of the building fabric, potential building damages, and the construction and planning law situation.
In addition, a building measurement and the creation of current as-built plans must always be carried out, as the old building application documents, if available, never represent the current building condition.
These preliminary investigations are carried out by an architect, possibly also involving a structural engineer.

The reusability of components/building materials should be viewed realistically: very rare, old building materials can be dismantled, cleaned, and prepared for reinstallation. It usually is not worthwhile. An old roof truss from the 1970s and a tile covering have no value that justifies the effort of refurbishment. With the reuse of old building materials, which do not correspond to common standards, the planner also takes a risk—his risk.

These preliminary investigations cost time and money, but are an essential prerequisite for a construction process that should be as free of surprises as possible. Surprises can never be excluded, but Pandora’s box can be kept small. Craftsmen are not planners, and free offers do not replace professional planning. Construction projects that have been planned and started in this way often end up in an organizational dead end with a very unsatisfactory result. In the last five years, I have experienced three such construction projects during building consultations that were "driven against the wall" in this manner. And that also cost money.

I recommend that you arrange an on-site building consultation appointment with an architect experienced in old buildings, have him assess the situation fundamentally, and, based on the available documents, name an initial rough cost framework. If necessary, you can then proceed with a more detailed cost estimate including area calculations and a sketch of the generally possible expansion for financing advice. Your approach and the financial conditions are, as far as described, realistic.

Dirk’s comments are also essential and should be taken into account in advance.