What Do Structural Calculations Include?

14. Beam Reactions

Once a beam is designed, the calculation can determine the forces transferred into its supports.

These are:

reactions.

For example:

B1

↙︎  ↘︎

R1  R2

Those reactions matter because the building beneath them must carry the load.

Why Reactions Matter to the Builder

Imagine the calculation says:

Left Reaction

40kN

Right Reaction

40kN

Those forces do not vanish at the end of the beam.

They pass into:

• masonry;
• padstones;
• columns;
• foundations.

15. Bearing Checks

Where a beam bears onto masonry, the support needs to carry the concentrated reaction.

The design may need to consider:

• bearing length;
• masonry;
• wall thickness;
• reaction;
• padstone.

What Is a Padstone?

A padstone is a structural element used to help distribute a concentrated beam reaction into the supporting masonry.

It can be:

• precast concrete;
• in-situ concrete;
• another suitably designed structural arrangement.

Does Every Steel Beam Need a Padstone?

No.

Whether a padstone is required depends on:

• reaction;
• masonry strength;
• wall construction;
• bearing arrangement.

This is why generic notes such as:

“Provide standard padstone to all steels”

should not replace structural design.

Does Every Beam Need 150mm Bearing?

No single dimension should be treated as a substitute for the structural design.

Typical domestic guidance may use commonly adopted minimum bearing arrangements, but the actual design should consider:

• loads;
• reaction;
• support;
• material;
• geometry.

Follow the project-specific structural specification.

16. Timber Beam Calculations

Not every structural member is steel.

Structural calculations can also design timber members such as:

• floor beams;
• roof beams;
• trimmers;
• lintels.

Checks can include:

• bending;
• shear;
• deflection;
• bearing.

17. Floor Joist Calculations

Floor joists may need to be checked for:

• span;
• spacing;
• loading;
• bending;
• shear;
• deflection.

This is particularly common in:

loft conversions.

Existing ceiling joists are often not automatically suitable as the new habitable floor structure.

Why Loft Floors Often Need Structural Design

A ceiling structure was not necessarily designed as a habitable floor.

A loft conversion can introduce:

• people;
• furniture;
• partitions;
• bathroom loads;
• floor finishes.

The new floor arrangement therefore needs to be designed appropriately.

18. Roof Calculations

Structural calculations can also cover roof members.

Depending on the project, these can include:

• rafters;
• purlins;
• ridge beams;
• trimmers;
• dormer beams;
• structural alterations to existing roof members.

When Are Roof Calculations Needed?

Examples include:

• loft conversion;
• vaulted extension roof;
• large rooflight;
• altered purlin;
• removed strut;
• dormer;
• unusual roof span.

19. Trimmer Calculations

Openings in floors and roofs often require:

trimmers.

Examples include:

• stair openings;
• rooflights;
• loft hatches;
• large service openings.

The surrounding members may need to carry loads that previously travelled through the removed joists or rafters.

20. Column Calculations

A steel beam may need to be supported by:

steel columns.

The column calculation can consider:

• axial load;
• bending where relevant;
• buckling;
• member capacity;
• restraint.

Why Columns Change the Scope

A simple beam sitting on two substantial masonry walls is one structural problem.

A beam supported on steel columns creates additional questions:

Beam

↓

Columns

↓

Base / Foundation

The load path has become more complex.

21. Steel Frame Calculations

Large structural openings can sometimes require:

• goalpost frames;
• box frames;
• other steel framing.

These can require calculations for:

• horizontal beam;
• columns;
• connections;
• stability;
• foundations.

What Is a Goalpost Frame?

A simplified goalpost arrangement is:

B1 horizontal beam

↓    ↓

C1  C2

The vertical members transfer the beam reactions towards the foundations.

What Is a Box Frame?

A box frame is a more extensive structural arrangement which can include:

• upper beam;
• columns;
• lower member;
• structural connections.

It can be required in some projects where the design needs additional:

• stability;
• load transfer.

22. Connection Calculations

Some structural systems require connections to be designed.

These can include:

• bolts;
• welds;
• end plates;
• fin plates;
• base plates;
• cleats.

Does Every Steel Beam Need Connection Calculations?

No.

A simple beam bearing directly onto masonry may have a much simpler support arrangement than a:

• beam-to-column;
• beam-to-beam;
• steel-frame

connection.

Are Connections Automatically Included?

Not necessarily.

The structural-design scope should state what is included.

A quotation for:

one beam calculation

should not automatically be assumed to include a complete multi-member steel-frame connection design.

23. Foundation Calculations

Structural calculations can include foundations where required.

A foundation design can consider:

• structural load;
• foundation type;
• size;
• ground conditions;
• bearing pressure;
• nearby influences where relevant.

Do All Extensions Need Bespoke Foundation Calculations?

Not necessarily.

Many conventional domestic foundations can be designed using established Building Regulations guidance and site-specific Building Control requirements without a bespoke engineering calculation for every strip foundation.

However, engineering input becomes more likely where there are:

• concentrated column loads;
• unusual ground conditions;
• trees;
• deep made ground;
• nearby structures;
• unusual foundation systems;
• high loads.

Is There a Standard Foundation Depth?

No universal foundation depth works for every house.

Foundation depth can depend on:

• ground;
• trees;
• drains;
• neighbouring foundations;
• frost;
• site history;
• structural loading.

A generic:

“1 metre is always enough”

rule is not reliable.

24. Pad Foundation Calculations

A steel column may need a:

pad foundation.

The calculation can assess:

• column load;
• foundation size;
• bearing pressure;
• structural design of the pad where relevant.

Can a Steel Column Sit on an Existing Concrete Floor?

Do not assume so.

A domestic floor slab may not have been designed to carry a substantial concentrated column reaction.

The support arrangement needs to be assessed.

25. Masonry Checks

Structural design can sometimes include checks relating to:

• load-bearing walls;
• concentrated reactions;
• masonry bearing;
• wall stability.

This can be important where:

• beam reactions are high;
• wall is thin;
• masonry condition is questionable.

26. Existing Structure Checks

Sometimes the project depends on an existing structural element.

Examples include:

• existing steel beam;
• existing wall;
• existing foundation;
• existing roof member.

The designer may need to assess whether it remains adequate for the proposed work.

Is Existing Structure Automatically Included?

No.

This is a major scope issue.

A new beam calculation does not automatically mean:

the entire existing house has been structurally surveyed.

If existing elements need assessment, that should form part of the agreed scope.

27. Structural Member Schedule

For projects containing several elements, the calculations or associated drawings may use a schedule.

For example:

Reference	Element
B1	Rear opening steel beam
B2	Internal steel beam
C1	Steel column
J1	New floor joists
T1	Stair trimmer
F1	Pad foundation

This makes it easier to coordinate calculations with drawings.

Why Structural References Matter

The Building Regulation drawing can show:

B1

and the calculation package can contain:

B1

The contractor can then identify exactly which calculation corresponds to which member.

28. Structural Sketches

Calculations can include sketches to clarify:

• spans;
• loading;
• beam arrangement;
• supports;
• dimensions.

These can be very useful.

But a calculation sketch should not automatically be confused with a full:

structural drawing package.

Structural Sketch vs Structural Drawing

A:

Calculation Sketch

helps explain the analysis.

A:

Structural Drawing

communicates the structural arrangement for coordination/construction.

The exact distinction depends on project complexity and deliverables.

29. Calculation Results

A structural calculation ultimately needs to reach a design conclusion.

For example:

B1

Selected section:

203 × 133 × 25 UB

with relevant support requirements.

Or:

J1

New timber floor joists:

specified section at specified centres

subject to the project design.

The calculation should make the required structural output identifiable.

What Does “Pass” Mean in Structural Software?

Structural-design software may show checks such as:

PASS

This means the element satisfies the particular design check performed using the inputs and assumptions entered.

It does not mean:

“the entire building is guaranteed structurally perfect.”

The result is only as relevant as:

• the structural model;
• inputs;
• assumptions;
• scope.

Structural Software Does Not Replace the Designer

Software can perform sophisticated analysis.

But somebody still needs to determine:

• what structure to model;
• what loads apply;
• what supports exist;
• what assumptions are appropriate;
• whether the result makes engineering sense.

Structural design is not simply pressing:

Calculate.

30. Design Standards

Structural calculations are prepared using appropriate:

• Building Regulations requirements;
• structural design standards;
• recognised engineering principles.

The standards used depend on:

• material;
• element;
• project.

For modern structural design this can involve relevant:

Eurocodes

and their associated UK National Annexes.

What Are Eurocodes?

Eurocodes are structural design standards covering areas including:

• basis of structural design;
• actions on structures;
• concrete;
• steel;
• timber;
• masonry;
• geotechnical design.

The appropriate standards depend on the calculation.

Do Homeowners Need to Understand Eurocodes?

No.

You do not need to become a structural engineer to commission structural calculations.

The calculation should be prepared by somebody competent for the work.

Your practical concern is:

Does the calculation clearly relate to my project and coordinate with what is being built?

31. Design Conclusions

A useful calculation package should allow the relevant people to identify:

• what structural element is required;
• what assumptions are important;
• what support conditions are required;
• what additional structural information applies.

The output needs to be usable.

What Structural Calculations Do Not Normally Include

This is just as important as what they do include.

A standard structural-calculation service does not automatically include everything involved in construction.

Structural Calculations Do Not Automatically Include Building Regulation Drawings

These are separate deliverables.

A calculation may design:

B1 beam

while Building Regulation drawings show:

• wall build-ups;
• insulation;
• ventilation;
• drainage;
• fire safety;
• roof construction;
• other regulatory information.

For larger projects, you may need both.

Structural Calculations Do Not Automatically Include Planning Drawings

Planning drawings serve a different purpose.

They normally show matters such as:

• layout;
• appearance;
• scale;
• site relationship.

Structural calculations are technical engineering documents.

Structural Calculations Do Not Automatically Include Fabrication Drawings

The steel fabricator may prepare:

• shop drawings;
• plate details;
• hole positions;
• fabrication dimensions.

These are separate from the structural calculation unless specifically included.

Structural Calculations Do Not Automatically Include Temporary Works

This is particularly important for wall removals.

The permanent calculation might design:

B1 steel beam.

But before B1 is installed, the existing building may need:

• props;
• needles;
• temporary beams;
• bracing.

Temporary works should be planned separately unless expressly included in the structural-design appointment.

Structural Calculations Are Not a Method Statement

A structural calculation does not automatically explain:

• demolition sequence;
• lifting method;
• site access;
• installation sequence;
• worker safety arrangements.

Those are construction-planning matters.

Structural Calculations Are Not a Structural Survey

A calculation is not automatically a survey of the entire property.

For example:

B1 steel-beam calculation

does not mean the designer has certified:

• every crack;
• every foundation;
• every roof member;
• every previous alteration.

The scope matters.

Structural Calculations Are Not a Building Control Approval

Structural calculations provide technical evidence.

Building Control independently assesses whether the proposed work complies with the Building Regulations.

The calculation itself is not:

statutory approval.

Structural Calculations Are Not a Completion Certificate

A completion certificate relates to the Building Control process after the work has been completed and the relevant requirements have been satisfied.

It is separate from the structural calculation.

Structural Calculations Are Not a Guarantee

A structural calculation does not guarantee:

• Building Control approval;
• workmanship;
• installation quality;
• undiscovered existing defects.

It designs the structural work within its agreed scope using the information available.

What Does Building Control Receive?

For a project involving structural work, Building Control may receive:

• Building Regulation drawings;
• structural calculations;
• structural drawings/details;
• specifications;
• other technical information.

The exact package depends on:

• application route;
• project type;
• structural complexity.

Does Building Control Read Every Calculation?

Building Control assesses the information needed to determine compliance.

It can:

• review calculations;
• raise queries;
• ask for clarification;
• request additional information.

The structural designer remains responsible for the design within their scope.

Does Building Control Recalculate the Beam?

Building Control is not your structural designer.

Its role is to assess compliance.

It may scrutinise:

• loads;
• assumptions;
• structural arrangement;
• member design;
• support details.

But the responsibility for producing the structural design remains with the appointed designer.

Can Building Control Ask for More Calculations?

Yes.

For example, you submit:

B1 beam calculation.

Building Control then identifies that B1 sits on:

C1 steel column.

It may ask:

How is C1 supported?

That could require:

• column calculation;
• base detail;
• foundation information.

This is why following the complete load path matters.

Does Full Plans Require Structural Calculations?

Where structural calculations are needed to demonstrate compliance, they are commonly submitted as part of the technical Full Plans information.

A typical Full Plans package can include:

• drawings;
• specifications;
• structural calculations.

What About Building Notice?

Building Notice does not involve formal approval of detailed plans in the same way as Full Plans.

But that does not remove the need for structural design.

Building Control can still request structural calculations and details.

Does Building Notice Mean I Can Skip Structural Calculations?

No.

If an element requires structural design, the application route does not make the engineering requirement disappear.

A steel beam still needs to be structurally adequate whether the project uses:

• Full Plans;
• Building Notice.

When Should Structural Calculations Be Prepared?

Ideally before:

• steel ordering;
• structural demolition;
• relevant construction;
• final builder pricing where the structure affects cost.

Why Before Builder Pricing?

Suppose you ask three builders to quote for:

“Remove rear wall and install RSJ.”

Builder A

assumes one beam.

Builder B

assumes beam + padstones.

Builder C

assumes goalpost frame + foundations.

You are not comparing the same scope.

Calculate First, Then Price

With structural design:

B1

C1 / C2 if required

F1 / F2 if required

the contractors can price a more clearly defined structural solution.

That can reduce ambiguity.

Why Before Ordering Steel?

Because the calculation determines the structural section.

Wrong sequence:

Guess beam

↓

Order steel

↓

Calculate afterwards

Correct sequence:

Define opening

↓

Calculate structure

↓

Coordinate support

↓

Confirm fabrication dimensions

↓

Order steel

Structural Calculations for Load-Bearing Wall Removal

A straightforward wall-removal calculation can include:

• beam loading;
• beam design;
• bending;
• shear;
• deflection;
• reactions;
• support requirements.

The exact scope depends on the building.

Example: 3m Internal Wall Removal

Existing wall supports:

• first-floor joists.

Proposed:

• 3m opening.

Potential calculation scope:

B1

steel beam.

R1 / R2

beam reactions.

PS1 / PS2

bearing/padstone assessment where required.

This can be a relatively straightforward structural-opening project.

Structural Calculations for a Large Rear Opening

Now consider:

5m rear-wall removal.

The project might require:

B1

main steel beam.

C1

left column.

C2

right column.

CN1 / CN2

connections.

F1 / F2

foundations.

That is substantially more design work than:

one RSJ calculation.

Structural Calculations for Extensions

Depending on the extension, calculations can include:

• rear opening beam;
• side opening;
• roof beam;
• lintels;
• columns;
• frames;
• foundations;
• unusual roof members.

Not every extension needs calculations for every element.

Structural Calculations for Loft Conversions

These can include:

• new floor joists;
• steel floor beams;
• dormer structure;
• roof beams;
• purlins;
• trimmers;
• stair opening;
• rooflight trimming;
• columns/connections where relevant.

Loft conversions can therefore involve a much wider calculation package than a single wall removal.

Structural Calculations for Garage Conversions

A simple garage conversion may require little bespoke structural calculation.

Calculations become more likely where the project includes:

• removal of structural wall;
• widened opening;
• new steel beam;
• questionable support beneath garage-door infill;
• roof alterations.

Structural Calculations for Double-Storey Extensions

These can become more involved because loads may travel through:

• upper floor;
• upper walls;
• roof;
• lower structure;
• foundations.

The structural load path needs to be coordinated through the building.

Structural Calculations for New Builds

A new house can require a much broader structural design package.

Depending on the construction, this may include:

• foundations;
• load-bearing walls;
• floor systems;
• beams;
• columns;
• lintels;
• roof structure;
• stability;
• connections.

This is not comparable with a standalone RSJ calculation.

What Information Does the Structural Designer Need?

This depends on the project, but useful information can include:

• existing plans;
• proposed plans;
• sections;
• elevations;
• dimensions;
• photographs;
• joist directions;
• wall construction;
• roof information;
• ground information;
• existing structural drawings;
• previous calculations.

Do I Need Architectural Drawings First?

Not always.

For a simple structural opening, it may be possible to work from:

• dimensioned sketches;
• photographs;
• measurements.

For larger projects such as:

• extension;
• loft conversion;
• new build;

proper architectural/technical drawings are generally much more useful.

Can Structural Calculations Be Prepared From Planning Drawings?

Yes, where the drawings contain reliable information.

Planning drawings can provide:

• geometry;
• dimensions;
• proposed layout;
• opening sizes.

Additional information may still be needed for structural design.

Can Structural Calculations Be Prepared Online?

For many suitable residential projects:

yes.

Reliable information can be provided digitally using:

• PDF;
• DWG;
• photographs;
• measurements;
• existing technical documents.

Do I Always Need a Site Visit?

No.

A site visit is not automatically required for every structural calculation.

It may become necessary where:

• existing structure cannot be reliably identified;
• masonry condition matters;
• hidden construction affects the design;
• measurements are uncertain;
• previous alterations complicate the load path.

What Happens If Information Is Missing?

The competent approach is:

ask for it.

Not:

guess.

The designer may request:

• more photographs;
• measurements;
• opening-up;
• site investigation;
• clarification from the client.

What If the Building Is Different From the Drawings?

The structural designer should be informed.

Examples include:

• joists running another direction;
• hidden wall above;
• existing steel discovered;
• different wall thickness;
• poor masonry;
• different foundation.

The design may need to be reviewed.

What If the Design Changes?

Structural calculations may also need updating.

Changes that can matter include:

• wider opening;
• different beam position;
• additional wall above;
• altered roof;
• changed column position;
• changed foundation arrangement.

How Do I Know Which Calculation Is Current?

Look for document control information such as:

• calculation reference;
• issue;
• revision;
• date.

The builder should work from the latest coordinated information.

How Long Are Structural Calculations?

There is no standard number of pages.

A straightforward beam calculation might be relatively concise.

A complex structural project might contain:

• dozens;
• hundreds

of pages of analysis and design output.

Length is not a measure of quality.

More Pages Does Not Mean Better Engineering

A 100-page software printout is not automatically better than a concise, clearly structured calculation.

The important questions are:

• Is the structural model appropriate?
• Are the loads appropriate?
• Are the important assumptions clear?
• Are the relevant checks included?
• Is the final specification identifiable?
• Does it coordinate with the project?

Can Structural Calculations Be Too Complicated?

They need to be technically adequate.

But good calculation documentation should also be:

• organised;
• identifiable;
• reviewable.

Building Control should not have to search through an unexplained software dump to determine which beam is actually being proposed.

What Makes a Good Structural Calculation Package?

A good package is:

Project-Specific

It relates to the actual building.

Clearly Referenced

Structural elements can be identified.

Based on Appropriate Information

Not arbitrary assumptions.

Technically Adequate

Relevant structural checks are undertaken.

Coordinated

The calculations match the drawings.

Reviewable

Building Control can understand the design basis.

Usable

The builder can identify the required structural specification.

Warning Signs in Structural Calculations

Be cautious if you receive:

No Project Address

You cannot easily identify what the document belongs to.

No Beam Reference

It is unclear which structural element has been designed.

No Loading Information

There is little indication what the beam is supporting.

No Reactions

Support design becomes difficult to understand.

Different Beam From the Drawing

The documents conflict.

Generic Calculation

It does not appear to relate clearly to the actual project.

No Revision Control

Nobody knows which version is current.

What Should I Check When I Receive Structural Calculations?

You do not need to verify the engineering yourself.

But you can check basic coordination.

1. Correct Address?

2. Correct Project?

3. Correct Opening Width?

4. Correct Beam References?

5. Do the Drawings Match?

6. Are Supports Identified?

7. Is the Current Revision Clear?

8. Has the Builder Received the Latest Issue?

These simple checks can prevent avoidable mistakes.

What Should My Builder Check?

Before ordering or installing structural members, the contractor should make sure the construction information corresponds with:

• site dimensions;
• current drawings;
• current structural calculations;
• relevant Building Control requirements.

If something does not match:

stop and clarify.

Do not improvise a structural change.

What Should the Steel Fabricator Receive?

Depending on the project, the fabricator may require:

• steel section;
• length;
• grade where specified;
• plates;
• holes;
• connection information.

Final fabrication dimensions should be coordinated with site conditions.

Is the Calculation Enough to Order the Steel?

For a simple beam, it may provide the required structural section.

But fabrication still needs accurate:

• length;
• dimensions;
• details.

For more complex steelwork, fabrication/shop drawings may be required.

How Much Do Structural Calculations Cost?

There is no universal price because structural scope varies enormously.

A project could require:

one beam

or:

a complete multi-member structural frame.

BuildRegs currently offers:

RSJ / Structural Opening Calculations

From £249

for suitable straightforward structural-opening projects.

The final fixed quote is confirmed after the scope is reviewed.

Why Does the Price Change?

Because the amount of structural design changes.

Compare:

Project A

One internal load-bearing wall.

Potential scope:

• B1 beam;
• reactions;
• supports.

Project B

Large rear opening.

Potential scope:

• B1 beam;
• C1/C2 columns;
• connections;
• F1/F2 foundations.

Project C

Loft conversion.

Potential scope:

• B1/B2 beams;
• J1 joists;
• T1/T2 trimmers;
• roof alterations;
• dormer structure.

These are not equivalent services.

Why a Fixed Quote After Review Is Better

A fixed quote can be based on the:

actual structural scope

rather than guessing from:

“I need an RSJ.”

Sometimes the drawings reveal that the project actually needs:

• two beams;
• column;
• foundation;
• frame.

Reviewing the information first reduces surprises later.

What Does BuildRegs Need to Quote?

Upload whatever you have.

This might include:

• PDF plans;
• DWG drawings;
• planning drawings;
• photographs;
• dimensions;
• Building Control comments.

The project can then be reviewed.

What If I Only Need One RSJ?

For a suitable straightforward structural opening:

RSJ / Structural Opening Calculations

From £249