First Decision: Plot Size and Zoning Status
The answer to the single-storey vs. two-storey question depends largely on your plot's conditions. Before deciding, you need two pieces of information:
- Floor Area Ratio (TAKS): This ratio, set by the zoning plan, determines what share of your plot you can cover with a building. For example, on a 500 m² plot with a TAKS of 0.30, you can build a structure with a footprint of up to 150 m².
- Floor Space Index (KAKS / Emsal): On the same 500 m² plot with an Emsal of 0.60, you have a total construction right of 300 m². Build two storeys and each floor can be 150 m²; build one storey and you can only use 150 m² in total.
Small plot or a high KAKS allowance → two storeys is more efficient.
Large plot or you want to use your full TAKS allowance → one storey is more practical.
Cost Comparison
Let's compare based on the same 150 m² of usable area:
| Item | Single-Storey (150 m²) | Two-Storey (2×75 m²) |
|---|---|---|
| Foundation area | ~180 m² | ~100 m² |
| Roof area | ~180 m² | ~100 m² |
| Floor slab | None | ~75 m² (steel joists + OSB + acoustic insulation) |
| Staircase | None | Yes (~25,000–40,000 TL) |
| Turnkey cost difference | — | 20-30% more expensive |
| Approximate cost (turnkey) | 3,300,000 – 3,900,000 TL | 3,900,000 – 4,800,000 TL |
In a two-storey home the foundation and roof shrink, but a floor slab is added: steel joists, OSB panel, acoustic insulation and reinforced structural framing. Stronger profile requirements and the staircase also add cost. Overall, a 20-30% extra cost for the same usable area is normal.
Construction Time Difference
| Single-Storey | Two-Storey | |
|---|---|---|
| Shell construction | 6–8 weeks | 9–12 weeks |
| Turnkey | 4 months | 5–7 months |
| Reason for extra time | — | Floor slab + second-storey assembly |
Structural Load and Safety
Light steel structures are built up to two storeys with standard systems under TBDY 2026. There are a few technical points to keep in mind for a two-storey structure:
- Profile thickness may increase: since the ground floor carries a greater load, its profile thickness may be greater than the upper floor's. This is determined in the structural calculation.
- OSB cladding is mandatory: in two-storey structures, OSB cladding is required on both floors; this provides rigidity and reduces floor vibration.
- Floor slab vibration: because light steel floors are lighter than reinforced concrete, a slight vibration can be felt while walking. This is minimized with acoustic insulation board and a minimum 150 mm joist spacing.
A two-storey light steel structure calculated under TBDY 2026 has the same earthquake safety level as a single-storey one. The structure's low weight (90% lighter than reinforced concrete) is also a major advantage in two-storey buildings — since earthquake force is proportional to structure weight, a lighter structure draws less force.
Living Comfort Comparison
| Criterion | Single-Storey | Two-Storey |
|---|---|---|
| Accessibility (elderly/disabled) | Superior (no stairs) | Requires stairs |
| Privacy (separate bedrooms) | Medium (rooms side by side) | Superior (bedrooms upstairs, living downstairs) |
| Heating efficiency | Easier (single zone) | Requires heating two floors |
| Garden use | Less garden (larger footprint) | More garden (smaller footprint) |
| View | Ground level | Wide view from the upper floor |
| Cleaning/maintenance | Easier | Stair cleaning adds work |
When Is Single-Storey Better?
- For elderly or mobility-limited residents, stairs are a real problem — single-storey should definitely be preferred.
- On a large, flat plot, a single-storey structure is the more common and practical choice.
- If budget is tight, single-storey is 20-30% cheaper for the same usable area.
- If fast delivery matters most, single-storey is delivered 4-6 weeks earlier.
- For holiday or seasonal use, single-storey requires less upkeep.
When Is Two-Storey Better?
- On a small plot, gaining more usable area effectively requires two storeys.
- For larger families (4+ people), two storeys works better for privacy and layout.
- For rental purposes, keeping the upper floor separate can provide rental income from two households.
- To fully use your KAKS allowance, two storeys provides more construction area.
- For long-term investment, two-storey homes carry a slightly higher resale value.
Examples from Real Projects
Two typical examples from projects we've completed as MefSteel:
140 m² usable area, 3+1, single storey, turnkey.
Plot: 400 m², rural area, large garden.
Duration: 110 days. Family: a couple with 2 children.
Why single-storey? A large plot and the grandmother in the family being unable to use stairs.
160 m² total usable area (ground floor 80 m² + upper floor 80 m²), for rental purposes.
Plot: 250 m², zoned area.
Duration: 160 days. Ground floor rented out separately.
Why two-storey? Small plot, maximum KAKS use and a dual-rental-income goal.
Decision Tree
| Situation | Recommendation |
|---|---|
| Plot 400 m²+ and TAKS sufficient | Single-storey |
| Plot under 300 m² | Two-storey |
| Family member aged 60+ or with mobility limits | Single-storey |
| Rental investment, two independent units | Two-storey |
| Tight budget, fast delivery a priority | Single-storey |
| Family of 4+, privacy matters | Two-storey |
| Holiday / seasonal use | Single-storey |
Frequently Asked Questions
Is a two-storey light steel home sturdy?
Yes. Two-storey light steel structures calculated under TBDY 2026 are fully safe against earthquake and wind loads. Hundreds of two-storey light steel structures are in trouble-free service across Turkey. Sturdiness comes not from the number of storeys but from the accuracy of the structural calculation.
How is acoustic insulation achieved in a two-storey structure?
A minimum 50 mm acoustic mineral wool panel is placed in the floor slab. An additional acoustic panel (for impact noise) can be applied over the OSB. With correct application, floor noise in a two-storey light steel structure becomes comparable to reinforced concrete.
Can a floor be added later?
Yes — this is one of light steel's biggest advantages. It's possible to convert a single-storey structure into a two-storey one later. However, this requires the ground floor's structural system to have been calculated for the extra load from the start. So if you anticipate adding a floor in the future, let us know at the initial design stage — we'll calculate the structure accordingly.
Does an attic count as living space?
That depends on local zoning regulations. In some areas, attic space below a certain height doesn't count toward the floor area calculation. If you're planning an attic floor or mansard roof, clarify the zoning status with the municipality in advance.
Let's work out together whether single-storey or two-storey suits you better based on your TAKS, KAKS and budget. Call 0553 543 02 12 or share your project details through the contact form.