Steel portal frame members
- Rafters and columns sized for gravity, wind and snow loads.
- Haunch lengths, knee and apex details suitable for fabrication.
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Steel buildings and sheds • Portal frame design
Portal frame – steel portal frame design, bracing and foundations
A portal frame is often the simplest way to create a wide, open building. We design steel portal frame members, bracing and foundations so your fabricator and Building Control know the structure is safe.
Each portal frame design covers rafters, columns, bases and stability under wind, snow and crane or mezzanine loads where needed.
- Steel portal frame members, bases and foundations designed as one system.
- Wind bracing and stability checked so the frame will not sway or rack under storm loads.
- Fixed fee calculation packs with clear drawings that fabricators and Building Control can follow.
We support small industrial units, workshops, farm sheds and extensions to existing portal frames across the UK, working with your architect, contractor or steel fabricator from concept to final design.
Portal frame – what we design for your building
We design the full steel portal frame system so the loads get from the roof and walls safely down into the ground.
Portal frame stability and bracing
- Roof and vertical bracing to stabilise the frame under wind.
- Portal frame roof bracing and tie members checked for tension and compression.
Connections and bases
- Design actions for eaves and apex connections for your fabricator.
- Base reactions for hold down bolts and column bases, including uplift and shear.
Foundations and pads
- Pad foundations sized for bearing, shear and overturning.
- Strip or ground beams where loads need to be shared between pads.
Extensions to existing portal frames
- New bays or lean-to frames tied into an existing portal frame.
- Checks on stability and load paths so the old and new frames work together.
Alterations, openings and cranes
- New door openings, mezzanines or local strengthening of members.
- Extra checks where internal cranes or heavy storage racks are planned.
Key points in portal frame design and analysis
These quick notes cover the questions we hear most often when clients are planning a steel portal frame building.
Load combinations and sway
Portal frame design is controlled by combinations of dead, imposed, wind and snow loads.
We check both strength and sideways sway of the frame so doors and cladding still work after it deflects.
Bracing and stability
Wind bracing is needed in the roof and walls to stop frames toppling like dominoes.
We set out bracing lines that work with doors, openings and cladding layouts.
Foundations and uplift
Wind suction can try to pull portal frame columns out of the ground.
Pads and bases are sized for uplift, sliding and rotation so the building stays anchored even in strong storms.
Information we need to design your portal frame
Clear information at the start keeps the portal frame design straight and avoids rework later.
Frame layout and dimensions
- Overall building length, span, eaves height and bay spacing.
- Any steps in roof, changes in height or lean-to frames.
Use, cladding and openings
- Building use, target internal clear height and any cranes or mezzanines.
- Door sizes and positions, cladding type and roof pitch.
Location and ground conditions
- Site address so we can apply correct wind and snow loads.
- Soil type, bearing capacity and water level if known.
Existing information and drawings
- Any previous structural drawings or frame models if this is an extension.
- Architect or fabricator drawings in PDF or DWG where available.
Portal frames – frequently asked questions
Short answers to the questions we hear most often about portal frame buildings and steel frame design.
What is a portal frame?
A portal frame is a rigid steel frame made from columns and rafters connected with moment joints at the knees and apex. It gives a clear internal space with few internal columns and is widely used for industrial and farm buildings.
Where are portal frames typically used?
Portal frames are common for warehouses, workshops, farm sheds, retail sheds and small industrial units. They are also used for single storey extensions to factories and storage buildings.
Do I need a structural engineer for a portal frame?
Yes. A portal frame must be designed by a structural engineer so that member sizes, bracing and foundations can resist wind, snow and imposed loads safely and meet Building Control requirements.
Can you provide design actions for connections only?
Yes. If your fabricator prefers to design their own connections, we can supply design actions and sketches for eaves, apex and base connections instead of full connection details.
How long does portal frame design take?
Simple single span portal frames can often be turned around within one to two weeks after we have full information. Larger or more complex frames with cranes or mezzanines take longer and we agree timescales at the start.
Portal frame design videos from our YouTube channel
For engineers and students, these short videos walk through portal frame prelim design, wind bracing and analysis models.
Easy method for portal frame preliminary design
Wind bracing sizes for portal frames
Analysis modelling methods for portal frames
Clients who used us for portal frame design
A few short comments from projects where we designed portal frames, bracing and foundations.
Farm building – Cheshire
New steel portal frame hay barn
“The frame design and pad layouts were clear. The steel fabricator said the reactions were easy to use and Building Control passed the structure without any issues.”
Workshop – West Midlands
Portal frame with crane beam
“They explained the effect of the crane loads in simple terms. The drawings made it clear how the bracing and crane beam should be fitted on site.”
Extension to factory – Manchester
New bays tied into existing frame
“SECalcs checked the old portal frame and designed the new bays so everything worked together. This saved us from guessing and gave Building Control confidence.”
Request a portal frame structural engineer quote
Use this form to outline your portal frame building or extension. Your enquiry goes straight to an engineer.
Tell us about your portal frame project
Share a few details so we can review the frame layout and ground conditions and confirm a fixed fee for your portal frame calculations.
This form connects to our central SECalcs email. You will usually hear back from a structural engineer within one working day.
Ready to move your portal frame project forward?
If you are planning a steel portal frame building or extension and want clear structural calculations for the frame, bracing and foundations, send us a few details and we will confirm the next steps and a fixed fee.
- Head Office: Corwell Lane, Uxbridge, England, UB8 3DE.
- 07359 267907
- info@structuralengineercalcs.com
- Company No: 12653163