Planning for semi-detached house, cost estimation

Hello,

we can buy a nice plot of land from the municipality, however it can only be built on with a semi-detached house. The development plan allows TH 6.50m, FH 11.00m and two full floors plus roof (gable roof or shed roof allowed). Frontage for our side southeast, the west wall faces the neighbor.

The building partner, with whom we have to agree (heights and roof pitch must be the same), can only build quite narrow and is currently planning a house 7.25 m wide and 9.50 m deep, i.e. our partition wall is then 9.50 m long. To reach approximately 140-150 m² living space with these dimensions, it is currently planned with 2 full floors plus attic (knee wall there then still 0.5 m, roof pitch 30°) as well as a utility basement. This makes the house overall very tall (TH 6.50 FH approx. 10.50 m). His current latest offer via a developer (solid construction, KfW70) amounts to €265,000 including ancillary costs. Is that realistic? Costs for the plot are not included, this is only about the house itself.

We are currently planning to have the house built by a local general contractor, whereby his proposal was to take over the planning, tendering, and construction management, but then select the craftsmen together with us and not offer the whole as a fixed total price including all profit and risk surcharges. We could save quite a bit this way (approx. 10%), but the risk would then be on us. We know the consultant quite well through various channels (friends, colleagues), I think he does not want to take advantage of us.

I find it difficult to make reasonable estimates for the total price now and hope to get some help here.

We are planning the following:
- Basement as living space (i.e. within the insulated area of the house)
- Ground floor with large kitchen/dining area (table for 8 people) and small living room (separable, suitable as guest room)
- Upper floor with 3 roughly equally sized rooms (approx. 15 sqm each) and family bathroom
- Attic with a studio room

Possibly we would like to take one meter off the south side of the 9.50 m length and instead put a gallery corridor in front of the window side, i.e. our building volume would then only be 8.50 m deep, but we could go up to approx. 10.50 m in width.

The ground and upper floors together should not significantly exceed 130 sqm, but will be finished (painting etc. as DIY), basement and attic remain unfinished at the beginning. It should preferably be a Kfw55 house. What minimum costs should be expected here if I take the following layout:
- Basement (slab + prefabricated concrete basement + basement ceiling), insulation outside and under slab
- Solid shell (e.g. 24cm Poroton over 2 full floors, footprint approx. 10 x 8.50 ceiling concrete?)
- Roof as gable roof 30°, rafter insulation
- Exterior insulation to achieve KfW55 (approx. 25 cm ETICS on Poroton sufficient?)
- Passive house windows (triple-glazed, plastic) mounted in insulation plane. The south side should be generously glazed to make good use of solar heat.
- Stairs from basement to attic
- Lightning protection (since we would then be the highest building on the hill)

The equipment does not need to meet high standards, normal standard is sufficient for us (e.g. tiles and sanitary equipment), for the floor on the ground floor we were thinking of industrial parquet. The interior walls should be plastered and painted.

- Heating technology
Here it gets complicated because I have ideas, but I do not know if they fit in combination and are cost-effective:
- Controlled residential ventilation with heat recovery (I am calculating here with approx. €11,500)
- Ground heat exchanger in intake air stream (approx. €1,500 (installation of ground loop in own work))
- Solar thermal system and 1000l buffer tank (we are 4 people) approx. €5,000
- Residual heating through gas boiler or pellet heating (more expensive but saves the gas connection) and underfloor heating.

Thank you very much for your help!

Hello

His most current offer from a developer (solid construction, KfW70) amounts to €265,000 including ancillary costs. Is that realistic?

No one can answer that in a serious manner because important details are unknown.

We are currently planning to have the house built by a local general contractor, whereby his proposal was to take over the planning, tendering and construction management, but then to select the craftsmen together with us and not to offer the whole as a fixed total price including all profit and risk surcharges. We could save quite a bit that way (about 10%), but the risk would then lie with us.
We know the consultant fairly well through various channels (friends, colleagues), I think he does not want to take advantage of us there.

Is there already an architect involved?

I find it difficult now to make reasonable estimates of the total price and hope for some help here...

No one can answer these questions seriously either, because you have many variables in your planning. More precise information is only possible once the planning and offer are finalized.

What strikes me is that you want to install a technology that I find unusual. Since you will have to tender and award the trades individually anyway, you should definitely have a TGA planning created before deciding on one technology or another; involve a TGA planner. Since you are personally responsible for every award and, in my opinion, do not have the greatest knowledge of efficient houses or renewable energies (as how could you), it would be safer to have someone at your side who is familiar with this.

Kind regards

Hello,
thank you very much for the quick response.

But there is already an architect involved, right?

Yes, there is. Behind the consultant is a large company that has been active in residential construction for over 20 years and, for example, has developed an entire area as a residential district in the area where our plot is also located. The planning would then be done by their architects and MEP planners.

No one can seriously answer these questions either because you have many variables in your planning. More precise information is only possible once the planning is done along with the offer.

This week we will receive a first offer, possibly also one from the provider of our construction partners.

What strikes me is that you want to install a technique that is, for me, unusual. Since you have to tender and award the trades separately anyway, you should definitely have an MEP plan created before deciding on one technology or the other; bring an MEP planner on board. Since you are personally responsible for any awarding and, in my opinion, don’t have the greatest knowledge about efficient houses or renewable energies (how could you), it would be safer to have someone on your side who is familiar with this.

That is probably because we are currently gathering a lot of information and certain ideas are swirling around in our heads. That is why I am asking here as well, since I am still not sure whether these really go together technically. Originally, I based it on the desire for a passive house, and there is one in the village with the mentioned technology (controlled residential ventilation with heat recovery, brine-earth heat exchanger, solar thermal energy and residual heating via wood stove with water jacket).
If we do not reach passive house standard (new goal KFW55), then that won’t fit, which is why I planned for a higher heating output here.
I generally consider controlled residential ventilation to be useful in a suitably airtight house; the earth heat exchanger is recommended on many information sites, especially since the cost is manageable. What do you consider recommendable?

In general, I still have the question whether awarding the trades individually is also recommended and whether savings potential can really be used that way (and if it actually is in the end), or whether rather bad experiences are made with this and a general contractor is the better option?

Thank you very much for your opinions.

Kniestock dort dann noch 0.5m, roof pitch 30°

No idea how tall you are or how you want to use the attic... but even 2m away from the wall, the room height is only 1.65m... With such a low knee wall, you need a steeper roof pitch if you want to use it properly as living space (at 45°, for example, it would already be 2.5m high at 2m distance from the wall).

Hello, after a long time I want to revive the article again, after long discussions with our construction partner (semi-detached house) we have a solution for the entire building that is fair to both. In the meantime, we also have a concrete offer from the construction company, which I would now like to put up for discussion here:

Semi-detached house with the dimensions 9.00 m x 8.25 m (gable side and semi-detached house wall is 9 m), gable roof with 38°. 2 full floors, knee wall in the attic 0.00 m) The semi-detached house will be basemented (expansion by own work), ground floor and first floor will be fully finished the attic is declared as expandable (stairs to attic will already be installed)

Price: €249,000 according to construction service description (which I unfortunately only have as a printout and not electronically)

Here are a few details from the construction service description (Energy Saving Ordinance 2009): Foundation: slab C20/25 d=12 cm

Basement: Basement outer walls also C20/25 in statically required strength and bulk density Basement inner walls made of calcium silicate masonry Basement windows plastic 1.1W/m²K, 80x60 cm, number according to plan (3x) including light shafts Thermal insulation according to construction service description 80 mm Basement floor height 2.375 (top of slab to underside of raw ceiling) Basement ceiling reinforced concrete solid ceiling made of precast panels

Shell construction: Floor height from ground floor 2.625 m from top of raw floor to underside of raw ceiling Outer walls two-shell (inner masonry made of hollow clay bricks, 17.5 cm, outside thermal insulation 14 cm Alternative offer for single-shell energy saving masonry made of clay bricks (Thermoplan) or aerated concrete (Hebel), wall thickness 36.5 cm possible

Party wall as two-shell soundproof masonry with separation joint Installation plastering for pipelines made of aerated concrete Floor ceilings like basement ceiling Roller shutter box made of cement-bonded lightweight panels with interior wall insulation

Exterior plaster: Thermal insulation composite system (Sto or equivalent, 14 cm B1 - WLG40 In the base area base insulation boards WLG35 with water-repellent mesh plaster. In single-shell construction 2-layer mineral exterior plaster

Carpentry work Roof truss made of construction timber, roof overhang eaves and gable each 50 cm Overhangs with visible boarding lying on the rafters (16 mm spruce), painting see painting work

Roof covering: Concrete roof tiles (Braas) Gutters and pipes made of titanium zinc sheet

Windows/front door: Plastic, 5-chamber profile (Schüco, Rehau) fittings Roto glazing thermal insulation glass in triple glazing (4/8/4/8/4 mm) U-value 0.7 W/m²K, sound insulation class II Front door wood with glass panel, electric door opener, aluminum fittings

Electrical: 15 circuit breakers, 4 FI switches Otherwise switches, sockets and cables according to plan Intercom system

Sanitary: Sanitary objects RENOVA or SANIBEL 3001 Fittings MEDIANO or Talis Drain pipes Geberit DB20 Bathtub steel enamel 1700 mm x 750 mm Shower tray 900 x 900 mm, depth 150 mm steel enamel 2x washbasin porcelain, approx. 60x48 cm 1x hand washbasin porcelain, approx. 45x35 cm Wall-hung toilets with in-wall cistern insulated (2x)

Heating: Natural gas-fired, condensing technology Buderus, approx. 120 l domestic hot water tank Flat radiators, underfloor heating on request (extra charge, see below) Solar system: 5.6 m² collector area (sufficient for up to 140 m² living area) Solar storage 300 l

Painting work: Paint wood outside (roof overhang) Filling Paint basement White painted textured wallpaper in living rooms

Tiles: Format 15/20 to 30/30, d=0.8 cm, laying normal bond, material price €25/m² Guest WC all around 1.20 m high, bathroom and shower room full height Floor tiles in basement hallway, hallway, vestibule, kitchen, bathrooms, guest WC, storage room

Floor covering Veneer parquet floor, manufacturer Bauwerk SLIMWOOD in living-dining room ground floor Carpet covering in all other rooms (€20/m²) Wooden baseboards

Plaster: Interior walls single-layer smoothed gypsum plaster

Dry plaster and insulation work Roof insulation 22 cm WLG35 Gypsum plasterboard 12.5 mm

Stairs Railing-supporting solid wood staircase manufacturer Kohler/Bucher model VIVA

Interior doors Laminate surface, approx. 4 cm thick, door leaf height approx. 198.5 cm Fittings aluminum manufacturer Hoppe (Verona, Bonn, ...)

I hope this is sufficient for assessment, I will try to scan the construction service description completely.

We now have the following extensions/changes in the offer:

Extension to KfW70:

1. Heating system - Heating as air heat pump, Stiebel Eltron type WPL for indoor installation including necessary control technology, buffer storage, etc. - Underfloor heating with individual room control instead of radiators, instead an electric towel heater in the bathroom - Gas boiler with exhaust gas duct Skoberne as well as solar system omitted Extra charge: €13,870

2. Additional insulation: - Increase of outer wall to 16 cm WLG35 instead of 24 cm WLG40 - Increase rafter height including roof insulation to 24 instead of 22 cm - Increase perimeter insulation of basement to 12 instead of 8 cm Extra charge €2,180

As a note it says that according to their experience the efficiency house 70 standard is achieved, but the verification would still have to be done.

Furthermore, we want to carry out part of the painting work (- €4,460) and flooring work (- €3,650) as own work.

Secondary construction costs (surveyor costs, approval and acceptance, connection fees, earthworks) are indicated at approx. €19,000

Garage and garden work are not listed, will be carried out as own work.

I now have a lot of questions about this: 1. Heating technology - useful? How ideally to combine with a controlled residential ventilation (costs?)? 2. Insulation and KfW70 realistic? 3. Total costs realistic or can/should something still be done?

Thank you very much

Hi, I just want to draw your attention to two points where we needed problems/coordination in advance: In the basement, you only have a ceiling height of 2.375 m – then another 20 cm will be lost for insulation + screed + flooring (you wanted to build a living basement) – so you end up with a room height of 2.17 m. I don’t know if you feel comfortable with that; from my point of view, it’s a bit oppressive, because outside there are concrete walls that aren’t really pretty,... If you finish the basement yourself (we did that too), you lay the electricity yourself – we then had the discussion about connecting the basement electricity to the meter cabinet. The builder’s electrician didn’t want to vouch for our basement electricity and only made the connection after I opened the distribution boxes so he could see what we had wired. You should clarify something like that in advance.