ᐅ Material costs for self-building a double garage

Hello,

Our house is planned to have a double garage, measuring 6 x 7.5 meters (20 x 25 feet). The floor area ratio is already fully utilized, so I would first need to check whether 6 x 9 meters (20 x 30 feet) would also be approved. In any case, the garage will have a flat roof and one door. The main gate will be a large sectional door with electric drive and remote control.

Quotes for a prefabricated garage were between 18,000 and 20,000 without the foundation. I then tried to create a material cost estimate for a self-build project and would appreciate your expert feedback on whether this list seems realistic. For the construction itself, I could rely on experienced all-rounders and masons.

==Building application==
Surveyor update of site plan 200
Building application under simplified approval procedure 50

==Foundation slab==
Concrete with strip footing 1400
Formwork 100
Gravel 1000
Excavator rental, 2 days 160
Reinforcement 200
Plate compactor rental, 2 days 80

==Walls==
Aerated concrete blocks, 21 cm (8 inches) 1500
Mortar 50

==Ceiling==
Concrete 900
Formwork + supports 200
Reinforcement 200
Roof membrane 120
Aluminum finishing strip 280

==Fixtures==
Sewage connection 50
Cables and light switches 50

==Gate/Door==
Gate with electric motor 3000
Metal door 200

==Wall finishes==
Interior plaster 150
Exterior plaster 150
Facing bricks for the front, 5 m² (54 ft²) 200

==Miscellaneous==
Miscellaneous 200
Tools 300
============
Total approx. 11,000

Thanks and best regards, Jens

As far as I know, a masonry garage is generally more expensive than a prefabricated garage. For my building project, I received quotes for 9x3m (29.5x10 feet) garages (single, not double) including door, window, electric drive, and all accessories ranging between 7,000 and 9,000 euros (without the foundation, which is usually offered to me for about 1,000 euros). Therefore, I can imagine that with some searching, you can find a supplier who can offer your shorter double garage for around 15,000 euros.

Why choose a concrete ceiling? Put a wooden shed roof on it instead, that will save you more. How large should the door inside be? We calculated 3 m x 2.75 m (10 ft x 9 ft) at €900. So €3,000 is already a high estimate. Is gravel that expensive in your area? It costs €40 for 3 tons (3 short tons) if you pick it up yourself at the gravel plant. Do you want to concrete the floor or pave it? Do you need a structural calculation for the garage in the building permit / planning permission process? The exemption procedure is not possible if you want to build it larger!

I roughly googled to estimate the prices and probably haven’t found the cheapest options yet, but I preferred to set the prices a bit higher. If you say that some of them are already priced on the high side, that would confirm my assumption. It should definitely be a concrete ceiling.
With double prefabricated garages, there is always the issue that the partition wall has such a frame and the whole thing looks assembled. That’s a disadvantage I’m not really fond of.