Portal Frame Structural Design Calculations • Bracing • Foundations • UK-Wide
Fixed-fee structural calculations for steel portal frame workshops, farm buildings, industrial units and frame extensions. Building Control-ready packs for your fabricator and inspector.
Get Your Fixed-Fee Portal Frame Quote
Describe your frame — we'll confirm a fixed price within one working day.
Full Portal Frame Design — Members, Bracing and Foundations
We design the complete steel portal frame system so your fabricator can order steel and Building Control can approve the structure.
Steel Portal Frame Members
Rafters and columns sized for gravity, wind and snow loads to BS EN 1993.
- Haunch lengths and knee/apex details for fabrication
- Member sections chosen for strength and sway limits
- Second-order effects included where required
Stability and Wind Bracing
Roof and vertical bracing designed to stabilise the frame against lateral wind loads.
- Bracing layouts coordinated with doors and cladding
- Tension and compression checks on bracing members
- Frame sway checked against deflection limits
Connection Design Actions
Eaves, apex and base plate forces for your fabricator to design the connections.
- Moment, shear and axial forces at all key joints
- Hold-down bolt forces including wind uplift
- Full connection design available if required
Pad and Strip Foundations
Foundations sized for bearing pressure, shear and overturning under all load combinations.
- Uplift and sliding checks included
- Ground beam options where shared pads are needed
- Reinforcement details for Building Control
Extensions and Alterations
New bays or lean-to frames tied into existing portal frame structures.
- Assessment of existing frame capacity
- Load path checks across old and new structure
- New door openings or local strengthening
Cranes and Mezzanine Floors
Additional checks where overhead cranes or heavy mezzanine storage decks are planned.
- Crane beam and corbel design
- Dynamic crane load cases applied to frame
- Mezzanine frame and connection design
From Enquiry to Building Control Approval
Most portal frame designs are completed without a site visit. Send drawings or dimensions and we handle the rest.
Send Your Brief
Share frame dimensions, site location, building use and any drawings. We confirm what we need to produce a fixed fee.
Fixed Fee Agreed
You receive a clear scope, fixed price and programme before any design work starts. No hourly rates, no surprises.
Calculations and Drawings
We produce the full structural calculation pack — members, bracing, connections and foundations — with drawings your fabricator can follow.
Building Control Support
We respond to Building Control queries and provide reasonable revisions until the structure is formally approved.
Information We Need to Start Your Portal Frame Design
Clear information at the start avoids rework and keeps the programme on track.
Frame Layout and Dimensions
- Building span, length, eaves height and bay spacing
- Any roof steps, lean-to bays or height changes
- Roof pitch or preferred pitch range
Use, Cladding and Openings
- Building use and any imposed floor or crane loads
- Door sizes and positions along each elevation
- Cladding type: steel sheet, timber, block, etc.
Site and Ground Conditions
- Full site address or postcode for wind and snow data
- Soil type and bearing capacity if a ground report is available
- Any known groundwater issues
Existing Structure (if Extending)
- Previous structural drawings if extending an existing frame
- Architect or fabricator drawings in PDF or DWG
- Photographs of the existing frame and foundations
Portal Frame Design Packages
Fixed prices agreed before any work begins. No hourly rates. No hidden extras.
Single Span Portal Frame
Members, bracing and pad foundations for a new single span building.
- Rafter and column member design
- Roof and wall bracing layout
- Connection design actions
- Pad foundations with reinforcement
Multi-Span / Complex Frame
Multiple bays, lean-to frames, stepped roofs or frames with valley beams.
- All spans and frame types included
- Valley gutters and lean-to rafters
- Full stability analysis
- All foundations designed as a system
Extension to Existing Frame
New bays or lean-to additions tied into your existing portal frame building.
- Existing frame capacity check
- New bay member and connection design
- Combined stability assessment
- New foundation design
Frame with Crane or Mezzanine
Portal frames with overhead travelling cranes or internal mezzanine storage decks.
- Crane beam and corbel design
- Dynamic load combinations
- Mezzanine frame and connections
- Enhanced foundation design
Portal Frame Design — From Our YouTube Channel
Short videos covering preliminary sizing, wind bracing and analysis models for engineers and informed clients.
Preliminary Design Method for Portal Frames
A quick approach to choosing starting member sizes before detailed analysis.
Wind Bracing Sizes for Portal Frames
How to size roof and wall bracing members so the frame stays stable under wind.
Analysis Modelling for Portal Frames
Comparing analysis methods and what they mean for real portal frame behaviour.
Portal Frame Projects We Have Designed
Comments from clients on farm buildings, workshops and industrial frame extensions across the UK.
"The frame design and pad layouts were clear and easy to follow. Our steel fabricator said the connection reactions were exactly what he needed, and Building Control passed the structure without any queries."
"They explained the crane load effects in plain terms and the drawings showed clearly how the bracing and crane beam should be fitted on site. Professional from start to Building Control sign-off."
"SECalcs assessed the old frame and designed the new extension bays so everything worked together. This gave Building Control the confidence to approve the structure quickly."
Portal Frame Questions Answered
Common questions from clients planning a portal frame building or extension.
A portal frame is a rigid steel structure made from columns and rafters connected with moment-resisting joints at the eaves (haunches) and apex. It creates a wide, clear internal space without intermediate columns — making it the standard structural form for workshops, farm sheds, warehouses and small industrial units across the UK.
Yes. Building Control requires structural calculations for all portal frame buildings. A structural engineer sizes the members, checks sway stability and wind bracing, and calculates the pad foundations so the frame is safe under all load combinations and complies with Building Regulations.
A simple single-span portal frame with pad foundations typically starts from £800. Multi-span frames, frames with cranes or mezzanines, and extensions to existing structures are priced on enquiry after reviewing the full brief. All fees are fixed and agreed before any work begins — no hourly rates.
Our portal frame packs include full structural calculations for members, bracing and foundations; an arrangement drawing showing column and rafter positions; connection design actions for your steel fabricator; and pad or strip foundation details with reinforcement. The complete pack is ready for Building Control submission.
A straightforward single-span frame is typically completed within one to two weeks of receiving all project information. More complex frames take longer — we agree a programme at the start of each project so your fabricator and contractor can plan around it.
A portal frame uses tapered I-section members with moment-resisting haunch joints, suited to larger agricultural, industrial and warehouse spans of 10–40 m. A goalpost or steel box frame uses RHS or SHS hollow sections with bolted connections, better suited to residential openings, garage conversions and smaller commercial applications. We design both — see our steel box frame and goalpost frame page.
Ready to Move Your Portal Frame Project Forward?
Send us your frame dimensions and site details. We'll confirm a fixed fee — usually within one working day.
- Head Office: Corwell Lane, Uxbridge, England, UB8 3DE.
- 07359 267907
- info@structuralengineercalcs.com
- Company No: 12653163