Cost estimate for knee wall construction and renovation on the existing structure

Hello,

I wanted to ask for your assessment of the cost breakdown from our architect. Preliminary information about the construction project:

Construction will be within an existing building

[*]Year of construction 1971
[*]Exterior dimensions approx. 13m x 11.50m
[*]Gable roof 33°
[*]A 1.20m knee wall will be built
[*]Change of room layout within the existing building
[*]Complete renovation

Construction site setup
Construction site setup including crane 4,800.00 €
Scaffolding work 3,500.00 €
Demolition work
Bricks approx. 210m² x 10€ 2,100.00 €
Battens, purlins, rafters approx. 210m² x 12€ 2,520.00 €
Gutters + downpipes approx. 23m x 15€ 345.00 €
Gable masonry approx. 35m² x 60€ 2,100.00 €
Dismantling windows, roller shutter boxes, front door, entrance stairs 3,700.00 €
Demolition of interior walls approx. 40m² x 20€ 800.00 €
Demolition of exterior masonry approx. 20m² x 40€ 800.00 €
Blocking up/cutting of chiseled components 30m x 15€ 450.00 €
Creating new stairwell opening in the ground floor ceiling 1,000.00 €
Demolishing floor coverings + screed on ground floor approx. 140m² x 20€ 2,800.00 €

Construction
Reinforcement steel 5,000.00 €
Ground floor: support pads, lintels, steel beams approx. 15m x 250€ 3,750.00 €
Masonry exterior walls new attic approx. 105m² x 90€ 9,450.00 €
Separation layer for masonry approx. 100m² x 8.50€ 850.00 €
Existing chimney raise 1,500.00 €
Ring beam approx. 65m x 60€ 3,900.00 €
Lintels approx. 13m x 85€ 1,105.00 €
Load-bearing interior walls attic approx. 29m² x 90€ 2,610.00 €
Non-load-bearing interior walls ground floor + attic approx. 80m² x 65€ 5,200.00 €
Roof
Roof truss approx. 11m³ KVH x 550€ 6,050.00 €
Carpentry approx. 390m x 8€ 3,120.00 €
Small metal parts 800.00 €
Eaves + verge boarding approx. 40m² x 36€ 1,440.00 €
Roof slope OSB boards approx. 150m² 3,600.00 €
Collar beam ceiling approx. 68m² x 95€ 6,400.00 €
Insulation roof slopes + collar beam ceiling approx. 220m² x 23€ 5,060.00 €
Roof battens approx. 210m² x 9€ 1,890.00 €
Verge + eaves boards approx. 58m x 6€ 348.00 €
Underlay membrane approx. 210m² x 10€ 2,100.00 €
Clay roof tiles approx. 210m² x 16€ 3,360.00 €
Ridge tiles approx. 13.8m x 39€ 538.00 €
Verge tiles approx. 30m x 30€ 900.00 €
Special tiles – penetrations 300.00 €
Vent pipe caps with flexible hose 400.00 €
Chimney flashing + cladding 1,200.00 €
4 roof windows with external shutters 6,800.00 €
Solar collectors approx. 4m² 3,800.00 €
Zinc gutters approx. 28m x 30€ 840.00 €
Rainwater downpipes approx. 8m x 35€ 280.00 €
Drain supports + bends 76.00 €
End drains + leaf guards 100.00 €
Front door canopy 1,760.00 €

Interior work
Front door system 6,200.00 €
Windows/doors with roller shutters and exterior window sills 28,000.00 €
Heating: condensing boiler 11,870.00 €
Underfloor heating ground floor + upper floor 8,600.00 €
Plumbing installation 7,600.00 €
Electrical 10,000.00 €
Decentralized ventilation system 8,770.00 €
Insulation of basement ceiling approx. 135m² x 18€ 2,430.00 €
Screed ground floor + attic 234m² x 20€ 4,680.00 €
Bathrooms 11,500.00 €
New stairs to attic 6,000.00 €
Interior doors 8 x 450€ 3,600.00 €
Floor coverings approx. 234m² x 60€ 14,040.00 €
Interior window sills 450.00 €
Interior plaster and painting work 12,000.00 €
Exterior plaster + insulation approx. 300m² x 87€ 26,100.00 €

Total costs: 271,282.00 €

What was completely neglected is the outdoor area, since the garden is already landscaped and fences are set up and will remain. What we still need to add:

Garage door: 6,000.00 €
Terrace: 5,000.00 €
Basement insulation outside and bitumen coating: 2,000.00 €
Paving driveway: 10,000.00 €

+ the "soft costs" of

Building permit fees 1,200.00 €
Architect for building application 5,950.00 €
Structural engineering and thermal insulation 3,000.00 €

and for internal calculation about 20,000.00 € for kitchen, lamps, and other furnishings

That brings us to a total of 324,432.00 €

A few questions are on my mind:
- How is it with the Energy Saving Ordinance, is exterior wall insulation mandatory as well as a ventilation system when renovating?
- Is a timber frame construction cost-neutral compared to masonry? What are possibly other advantages and disadvantages? (Our main previous argument for timber frame construction is the speed as well as the easier change of room layout if necessary)

Thanks!

I am attaching the current plans again to possibly better estimate the costs.

- Is a timber frame construction cost-neutral compared to masonry?

If I understood correctly, the ground floor remains in its basic substance (i.e., it only undergoes minor interior wall changes), and the upper floor is converted from the attic into a living floor and is effectively raised at the knee wall by its ridge beams. It does not have interior walls yet. I wouldn’t think of tearing down the gable walls and placing a timber-framed upper floor on a masonry ground floor. Instead, I would build up the gable walls, masonry the load-bearing wall (above the same in the ground floor), and otherwise open it up for drywall (or gypsum boards in the bathroom, if applicable). So: gypsum board between the hallway and bathroom, drywall between the children's rooms and between bedroom and dressing room as well as the study, and the "rest" masonry as downstairs.

Thank you for the idea! To be honest, that sounds pretty logical. Additionally, we would save about 12 cbm of debris, which would cost us around 800.

Would we come to about 90k for the construction and roof?

Thanks for the idea! Honestly, that sounds pretty logical.

However, the architect should not do it significantly differently without me. Transforming the "existing gable walls" into the "new gable walls" can sometimes be cheaper than demolishing them up to the ground floor ceiling; without photos, I don't want to claim otherwise, as the architect has the advantage of local knowledge of the specific site. But continuing above with the same exterior wall building material as before is basically standard and hardly any smarter otherwise.

Everyone has their own "style" here, and in 1971 I probably would have mostly built the interior walls in the attic with masonry, but today the craftsmen are different, drywall is more common. The load-bearing wall above is located above the lower one, so it is unproblematic to construct with the same material; and it is parallel to the ridge, so no fiddly stepping required. Between the children's room and the stairs, you then have the fiddliness on the slope above, but overall I would tend to go with masonry there; likewise between the study and children's room. Between the bathroom and hallway, you can then deviate from my preference and use drywall, as well as between the study and bedroom or the bed and dressing area; after all there is also "green" plasterboard.

Many single-family house architects "lack" the more rational thinking of developers and apartment builders, they are a bit more romantic oriented, less technical.

Go ahead and post some photos as well.

I can't contribute anything to the costs, but I would reduce the pantry or leave it out entirely in favor of a more open feeling. I think the corridor to the kitchen has something of the narrow part of an hourglass. It feels like you get stuck there.