Offer · Design
Timber structure calculated, not guessed.
The structural engineer designs what holds the house up: the wall frames, the floor, the roof structure and the trusses. We calculate to Eurocode 5 and draw so that the carpenter never has to guess. For investors, architects and contractors.
What our structural engineer does
- 01
Structural analysis
Walls, floors, roof structures, trusses, headers and posts: capacity and deflection under code loads, with the snow and wind zone of your plot.
- 02
Working drawings of the structure
Drawings of every wall and floor with numbered elements, material schedules, connection details. Also for designs from other studios.
- 03
Roof structures and trusses
A traditional roof or nail-plate trusses, also for halls, shelters and farm buildings: spans up to 15 m without intermediate supports, 20 m on request.
- 04
A masonry design as a timber frame
Have a masonry design from a catalogue or from another architect? We recalculate the structure as a timber frame, keeping the layout and the massing.
3D model
Turn a structure we designed.
A house in Matysówka near Rzeszów, straight from the working drawings: every stud, header, rafter and collar tie in its place. Turn it, zoom in, click a member or its name and every member of that kind lights up on the model.
Click a member on the model or its name above: every member of that kind lights up lime and the camera moves to where they show best.
- 553studs in the walls
- 134headers
- 85rafters and jack rafters
- 61floor joists
The model straight from the timber design software, slimmed to 0.6 MB. The numbers are counted from the same file.
Tool
Pick a floor joist from our stock.
Span, spacing and use: we check which C24 joist from our stock passes, calculated the way a structural engineer does. The pick is indicative; one click sends it to us to confirm.
The calculations on this page are estimates only and are not a basis for any construction work. The joist for your build is chosen by the structural engineer in the design.
| Section | Bending | Shear | Deflection | Result |
|---|---|---|---|---|
| 45 × 95 mm | 703 % | 164 % | 2265 % | Too weak |
| 45 × 145 mm | 329 % | 108 % | 639 % | Too weak |
| 45 × 170 mm | 242 % | 92 % | 398 % | Too weak |
| 45 × 195 mm | 184 % | 80 % | 264 % | Too weak |
| 45 × 220 mm | 145 % | 71 % | 184 % | Too weak |
| 45 × 245 mm | 117 % | 64 % | 134 % | Too weak |
| 2 × 45 × 195 mm | 93 % | 41 % | 134 % | Too weak |
| 2 × 45 × 220 mm | 73 % | 36 % | 94 % | Tight, no margin |
| 2 × 45 × 245 mm | 59 % | 33 % | 68 % | Our pick |
| STEICOjoist, I-joist | from the maker's data | beyond 5.2 m or when C24 is not enough | ||
| LVL, laminated veneer lumber | from the maker's data | beyond 5.2 m or when C24 is not enough | ||
Your floor
Send this pick to the engineer.
The table knows nothing about a partition wall, a chimney or a bathtub. Leave the parameters and a contact: the engineer checks the layout, the loads and the supports and confirms or corrects the section, no strings attached.
Floor joist sizing from asasak.pl: span 4.0 m, spacing 60 cm, Living floor. The table gives 2 × 45 × 245 mm C24 (utilisation 68 %).
How do we calculate it?
- Load
- Living floor: the permanent 2.5 kN/m² is what our structural engineer takes, with a margin for the deck, the ceiling, the floor layers and the partitions (the joist's own weight is added separately from its section, 4.2 kN/m³ for C24); the imposed 2.0 kN/m² is category A of EN 1991-1-1 (rooms in dwellings); deflection up to L/300 so the floor does not spring. Design: (1.35 × 2.5 + 1.5 × 2.0) kN/m² × 0.6 m + 1.35 × the joist's own weight 0.09 kN/m = 3.95 kN/m. Characteristic, for deflection: 2.79 kN/m. Simply supported beam, uniform load.
- Beam length
- C24 timber in stock comes up to 5.4 m long. Less 10 cm of bearing at each end that leaves 5.2 m of span; longer floors are made of STEICOjoist I-joists or LVL beams, calculated from the maker's data.
- Bending
- M = w L² / 8 = 7.90 kNm. Stress σ = M / W = 8.8 MPa ≤ f_m,d = 24 × k_h × 0.8 / 1.3 = 14.8 MPa (C24, service class 1, medium-term load).
- Shear
- V = w L / 2 = 7.90 kN. τ = 1.5 V / (0.67 b h) = 0.80 MPa ≤ f_v,d = 2.46 MPa (k_cr allows for cracks in the timber).
- Deflection
- u = 5 w L⁴ / (384 E I), E = 11000 MPa. Instantaneous under the whole characteristic load: 7.7 mm ≤ L/300 = 13.3 mm. Final with creep: permanent part × (1 + 0.6), imposed × (1 + 0.3 × 0.6) = 10.9 mm ≤ L/250 = 16.0 mm.
A simplified pick to PN-EN 1995-1-1 for a simply supported beam: service class 1, medium-term imposed load (k_mod 0.8), compression edge braced by the decking (no lateral-torsional check), no floor vibration, bearing, connections or point loads. Deflections are checked cautiously (L/300 and L/250) and the section is picked with a margin: utilisation up to 90 %. In the design the joist gets its own calculation for the real layout and loads.
What we check
Seven things that have to add up.
- Bending capacityBeams, rafters, headers: the stress in the most heavily loaded section.
- Shear and bearingThe zones at the supports, where timber splits along the grain or crushes.
- DeflectionInstantaneous and final with creep, so the floor does not bounce and the plaster does not crack.
- StabilityLateral buckling of beams, buckling of studs and the bracing of walls against wind.
- ConnectionsNails, screws, carpentry joints and nail plates: each with a capacity, not out of habit.
- Floor vibrationSpan and stiffness chosen so that footsteps in one room are not felt in the next.
- Loads from the plotSnow by zone and altitude, wind by terrain, the weight of the roofing you choose.
What we calculate against
- PN-EN 1995-1-1Eurocode 5: design of timber structures
- PN-EN 1991Eurocode 1: actions, including snow and wind by zone
- PN-EN 338strength classes of structural timber, C24 among them
- PN-EN 14250prefabricated trusses with punched metal plate fasteners
Who it is for
For investors, architects and contractors.
Investor
You have a design or an idea and want a house that stands on calculations, not assurances. You get documentation our crew or yours builds from.
Architect or design studio
You design the massing, we calculate the timber structure and draw the frame. We work on your files and agree details and dates.
Contractor
You build frames or roofs and need working drawings, calculations for the permit or trusses with their documentation.
Contact
Send the project, we reply with a quote.
A PDF with plans and sections is enough, or a description of what you are planning. We reply with the scope, the date and the price.
You can also send the files to biuro@asasak.pl. See the Architecture page too
Let's talk
Your structure could be next.
Design, structure and materials from one company. Call or write. An advisor will tell you where to start.