Not sure whether you need a simple beam calculation or full structural design? This guide walks through common domestic projects and explains exactly what you'll need.
Scenario 1: Removing a Load Bearing Wall
Your project:
Opening up your ground floor by removing the wall between kitchen and living room. The wall supports the first floor and roof above.
What structural work is needed:
- Replacement beam: A steel or timber beam to carry the loads previously supported by the wall. This is typically a Universal Beam (UKB) sized to the span and loading.
- Padstones: Concrete or dense blockwork bearing pads at each end to spread the load into the masonry.
- Temporary support: Acrow props or strong boys to hold the structure while the wall is removed and the beam installed.
What Building Control want to see:
- Structural calculations showing the beam can carry the design loads (permanent + variable)
- Construction drawings showing beam size, position, padstone dimensions, and temporary works
- Specification of materials (steel grade, concrete strength)
- Proof that loads transfer safely down to foundations
What FM Structural provides:
- Standard Beam Calculation (£195-£295): For straightforward wall removals in typical construction. You get calculations, construction drawing, material specification, and temporary support details.
- If Party Wall applies: We can serve notices and handle party wall compliance (from £150)
Scenario 2: Single-Storey Extension
Your project:
Adding a 4m x 3m single-storey rear extension with a flat roof, knocking through from the existing kitchen.
What structural work is needed:
- Foundations: Typically 600mm wide strip footings to 1m depth (subject to ground conditions)
- Floor slab: 100mm concrete slab with damp proof membrane and insulation
- Walls: Cavity wall construction (brick outer, blockwork inner)
- Roof structure: Timber joists or steel beams supporting flat roof deck and weathering
- Opening beam: Steel beam where you knock through to existing house
What Building Control want to see:
- Foundation design calculations and drawings
- Floor slab specification
- Wall construction details
- Roof structural calculations and layout
- Opening beam calculations
- Thermal performance calculations (Part L compliance)
What FM Structural provides:
- Full Structural Design Package (£450-£650): Complete calculations and drawings covering foundations, floor slab, walls, roof structure, and opening beam. Suitable for Full Plans Building Regulations application.
- If ground conditions are poor or unknown, we can recommend a soil investigation and design foundations accordingly.
Scenario 3: Loft Conversion
Your project:
Converting your trussed-rafter roof space into a bedroom and en-suite. You'll need to remove some of the existing trusses and create headroom.
What structural work is needed:
- Roof alterations: Steel beams to replace the structural function of removed truss members. This often involves a ridge beam and supporting posts down to load-bearing walls.
- Floor strengthening: Existing ceiling joists (typically 100×50mm) are not designed as floor joists. You'll need to double them up, add new joists, or install steel beams.
- Staircase opening: Trimmer joists and possibly a steel beam to create the stair void.
- Dormer (if applicable): Structural frame for dormer window, including lintel over opening and valley beams.
What Building Control want to see:
- Roof alteration calculations and layout drawings
- Floor joist calculations (with deflection checks for vibration)
- Staircase opening structural details
- Dormer frame calculations (if applicable)
- Load paths showing how loads transfer to existing structure and foundations
What FM Structural provides:
- Full Structural Design Package (£550-£850): Comprehensive calculations and drawings for roof alterations, floor strengthening, staircase opening, and dormer (if applicable). Includes review of existing structure and recommendations for strengthening.
- If the existing structure shows signs of movement or distress, we can carry out a structural survey to identify issues before you commit to the conversion.
Scenario 4: Two-Storey Extension
Your project:
Adding a two-storey side extension, extending kitchen on ground floor and adding a bedroom above.
What structural work is needed:
- Foundations: Deeper and wider than single-storey due to higher loading
- Ground floor slab
- Ground floor walls: Designed to carry first floor + roof loads
- First floor structure: Timber joists or beam-and-block floor
- First floor walls
- Roof structure: Pitched roof tied into existing roof, or independent structure
- Opening beams: Where you knock through at ground and first floor levels
What Building Control want to see:
- Complete structural package from foundations to roof
- Calculations for all load-bearing elements
- Construction drawings showing floor plans, sections, and critical details
- Integration details showing how new structure ties into existing
What FM Structural provides:
- Full Structural Design Package (£750-£1,200): Comprehensive calculations and drawings for the entire extension, including foundations, floors, walls, roof, and opening beams. Includes details for tying new work into existing structure.
- We can coordinate with your architect to ensure structural design aligns with architectural intent.
Scenario 5: Just Need a Padstone Calculation
Your project:
Building Control has asked for padstone calculations for an existing beam that's already installed, or your builder needs confirmation of padstone size before ordering materials.
What FM Structural provides:
- Padstone Calculation (£95-£150): Quick turnaround calculation showing padstone dimensions, bearing length, and reinforcement if needed. Suitable for retrospective Building Control approval or pre-construction confirmation.
Scenario 6: Party Wall Act Compliance
Your project:
Any of the above scenarios, but the work affects a shared wall with your neighbor, or you're excavating within 3 meters of their property.
What the Party Wall Act requires:
- Written notice served on adjoining owners at least two months before starting work
- Description of the proposed work
- Drawings showing what you're doing
- If your neighbor dissents (or doesn't respond), surveyors are appointed to agree a Party Wall Award
What FM Structural provides:
- Party Wall Notice Service (£150-£300): We prepare and serve the required notices on your behalf, including drawings and descriptions.
- Party Wall Surveying (from £800): If a dispute arises, we can act as the Building Owner's surveyor to negotiate the Award.
- Party Wall services are often bundled with structural design—if you need both, we offer a package rate.
Quick Decision Guide
Choose Standard Beam Calculation if:
- You're removing a single wall in typical construction (cavity wall, timber floor, standard roof)
- The span is straightforward (under 4.5m)
- No complications (no existing movement, ground is stable, construction type is known)
Choose Full Structural Design if:
- You're building an extension (any size)
- You're doing a loft conversion
- You're removing multiple walls or creating a large opening (>4.5m)
- The property is non-standard (timber frame, pre-1919, listed building)
- There are complications (existing cracks, unknown foundations, poor ground)
Add Party Wall services if:
- You're working on a shared wall
- You're excavating within 3m of your neighbor's structure
- You're building a new wall on the boundary
Still Not Sure?
Submit an enquiry with photos and a description of what you're doing. We'll review it and recommend the appropriate service level. If you've selected a higher service tier than necessary, we'll tell you—we don't upsell.
You can also use our template gallery to identify your project type and get an instant indication of what's typically needed.
