Old building with architectural planning from 2020 - cost estimate update

Hello forum community,

I have recently been quietly reading along and have already been able to pick up some good advice/tips: thank you! I have also read a bit of background information regarding my current concern, but I am now reaching the limits of the information puzzle.

First, I would like to introduce myself (us): We are a small family consisting of dad (37), mom (31), and baby (1.5) and live in a suburb of Dresden – where the sun usually shines on the beautiful vineyards – in a rental apartment that is very nice for three seasons of the year. For about a year now, we have put the topic of "own home" on a prospective wish list. In principle, the original idea was a "good used property" (modernization yes, renovation no, new build no). Basically, we pull down the "allegedly highest millionaire density in Germany" and thus don’t have a corresponding budget – and although the (public) offer has improved with rising interest rates, the selection is still very limited. In addition, the housing stock here is generally very beautiful (villa area) – but also very old (120 years+ is not uncommon).

What this is about today: A local realtor offered us a house, which we declined due to the location. The same realtor then looked into his portfolio and drew our attention to another offer that looks very interesting:
- Location: very nice
- Plot: very large (930 m²)
- Price: okay?
- Size: very small (88 m² living + 37 m² usable space)
- Condition: hmm… major renovation

In numbers: semi-detached house, built in 1902 (architectural design) or 1940 (exposé), energy efficiency class F (approx. 200 kWh/m² a, gas). The price including ancillary purchase costs is roughly at the land value. The current owner commissioned an architect in 2020 to plan the extension and conversion – and thereby apply for a building permit (which was granted / is still valid or was just extended again). I was allowed to look at the plans: a very nice overall concept – the currently somewhat “botched” semi-detached house (on the half to be purchased there is a “GDR flat roof annex” added) will be restored to a symmetrical, very beautiful house. We may have different wishes in details (room layout) (certainly easily adaptable) and overall the semi-detached house will have more space after renovation than we actually need. But if we – or someone else – ever implement the plans, the house will become a beautiful gem.

My main concern: I would like to create a first rough cost estimate ("on a beer coaster") to check whether the project even lies within our financially feasible range. My previous rough estimates unfortunately showed a range from "feasible" to "much too big for us."

Approach 1: Tailor-to-Need
- Initial consideration, before looking at the architectural plans, exposé area data
- 88 m² living area x 2000 EUR/m² major renovation
- 37 m² usable area x 1000 EUR/m² light renovation
- 50 m² new living area (extension) x 3000 EUR/m²
- 50k EUR miscellaneous (land survey, architect, new infrastructure from road)
=> Total: 413k EUR (category: too big for us)
[Footnote: Please also comment on the assumptions for renovation/construction costs – are these realistic or exaggerated expectations?]

Approach 2: Architectural plans x Pippi Longstocking factor
- KG300 (100k EUR) + KG400 (20k EUR) + KG500 (2.7k EUR) + KG700 (12.1k EUR) = 134.8k EUR
- Basis: early 2020 → googled construction cost curve, got alarmed, took start point "x1.5"
=> Total: 135k x 1.5 = 202k EUR (category: feasible)

Approach 3: Architectural plans x
- Existing areas according to architect: 71 m²
- New build areas according to architect: 105 m²
- Not included: existing basement areas
- Googled renovation costs and found one hit "cost example: this is how much house construction costs" from a large building society based on a KFW40-130m² new build, thus energetically overshooting the target (= too high?), but also for a plain vanilla new build without additional expenditure for existing renovations (= too low… or overall okay?), in detail:
- Renovation existing: house installation (230 EUR/m²) + roof (230 EUR/m² - 50% of new build price) + interior finishing (500 EUR/m²) = 962 EUR/m²
- Extension new build: house installation (230 EUR/m²) + roof (461 EUR/m²) + walls (962 EUR/m²) + interior finishing (500 EUR/m²) = 2150 EUR/m²
- Flat-rate costs: land survey (30k EUR), heating (25k EUR), windows (35k EUR), ventilation (8k EUR – guesswork?), bathroom/sanitary (15k EUR) = 113k EUR
=> Total: 68k EUR (renovation) + 226k EUR (new build) + 113k EUR (flat-rate items) = 407k EUR

Questions:
1) What cost sizes would you use for a budget estimate?
2) What is a reasonable energetic target condition? (The building only has two permanent, small existing exterior walls + partition wall to the other semi-detached house and is otherwise complemented by the new/extension on the large/long wall.)
3) How does 2) then influence 1)?
4) Why do approaches 1+3 differ so much from approach 2 → is the factor 1.5 chosen too low? For crystal ball possessors: did the architect underestimate? Or does it depend too much on the specific plans… and the next step inevitably has to be the path to a professional who looks at the exact details, checks current prices, and possibly also advises on cut/reduction options?

Regards
MrMunki

1) What cost sizes would you use for a budget estimate?

Approach 1 sounds the most realistic to me.

2) What is a sensible energetic target state? (The building has only two remaining, small existing exterior walls + partition wall to the other semi-detached house and is otherwise supplemented on the large/long wall by the new extension.)

Well, if you're renovating it anyway, then look where you come out well including subsidies.
Presumably something around KFW55EE makes sense. Then you get up to €150k credit plus a 20% repayment bonus. (+ construction supervision)

What about the other semi-detached house, is something supposed to be done there too or will it remain as it is?

3) How does 2) then influence 1)

Less than you think. You have to tackle everything anyway. Then you might as well insulate properly. Insulating when you have to do it anyway is the most cost-efficient approach.

Take approach 1 and add a safety buffer. If REALLY EVERYTHING is done during the major renovation, the 2,000€/sqm might not be enough (or will even probably not be enough).

4) Why do approaches 1+3 deviate so much from approach 2

Because approach 2 is only a renovation and you simply omit 50sqm of new construction. Then you are also above €350k. So everything is comparable.

Is there an online exposé to get an impression? What is the asking price of the DH?

Does the new construction really have to happen? No one is forcing you to implement someone else's plans. If it has to be (Bedarf?), maybe it can be done later?

Hello everyone,

thanks already for the feedback:

Approach 1 was before reviewing the architect’s planning, i.e. the very first assumption of "the house offers 88 m² – too little – so you just add 50 m²". The architect plans to demolish half of the existing structure (the DDR extension) and build more new substance instead. If you detach yourself from the existing plans and say "yup, it’s too big (not feasible)" and make a new plan based on a more suitable (smaller) total area, you would rather aim for the areas assumed here (+/-, a clever architect will surely find another optimum for the smaller demand). Here I’m then surprised that approach 3 (which assumes the >200 m² total area of the existing renovation plan) ends up with a comparable number.

Approach 2 is not just renovation, but the package of 90 m² substance -> 50% demolition -> 81 m² (gross floor area) new build. But with a cost basis from 2020 – and I have also seen email correspondence where the architect says things like "...renovation forgotten..." and "...prices no longer realistic..." on his fee invoice (the latter would be reflected in my 1.5x factor... if that is realistic... if the renovation isn’t included and comes on top, you quickly get to >/=100k EUR extra... hmm).

: Exposé is currently offline (according to the realtor deactivated at the owner’s request: no sales pressure, accessible for fair offers, no desire for lowballing). I think I once heard in the forum of a site where you can look at old exposés? Unfortunately, I forgot the name, otherwise I could check there. The asking price is just under 400k EUR (+additional costs: 5.5% tax, 3.57% realtor, 2% notary/land registry). The standard land value is 465 EUR/m² (x930 m² = 432k EUR).

: From my point of view, it won’t work without new construction -> about half of the 88 m² is in the "DDR extension", where it’s not worth investing money and which is only usable as a hallway/anteroom/storage space. That leaves about 45...50 m² of the original substance, which neither fits our spatial requirements nor the possible floor plan design -> that would be a huge step backwards compared to the rental apartment. One of our challenges is, among other things, that our rental apartment (except in winter, when we watch the heating costs escape through windows and walls) is very nice and in a prime location: So there is no urgent need for action on our part – either the overall package fits, or we’ll just stay here longer and keep looking.

Best regards
MrMunki