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Structural work for renovations

Structural calculations and drawings for a safe renovation

Are you renovating and changing something in the load-bearing structure of your home or building? Then it is important to establish in advance how the loads will be safely absorbed and transferred.

Removing a wall, creating a wider opening, adding a stairwell or building an extension may seem structurally simple. In structural terms, however, such a change can have consequences for floors, joist layers, façades, foundations and other load-bearing components.

ROMB provides the structural design for private renovations and small-scale building projects — from the initial assessment to structural calculations, structural drawings and construction details for the contractor or permit application.

Discuss your renovation

When do you need structural work?

Not every renovation requires a structural engineer. However, as soon as you remove, relocate, load more heavily or add a load-bearing component, a structural assessment is advisable and often necessary.

Think, for example, of:

We assess how the existing structure works and which structural provisions are needed to carry out the intended renovation safely.

Structural solutions for your renovation

Removing a load-bearing wall

Removing a load-bearing wall is one of the most common structural interventions in home renovations. When a load-bearing wall is removed, the load from the floor, wall or roof structure above must be taken over by another structure.

This is done, for example, with:

We determine which loads rest on the wall and then calculate the required beam, columns, supports and connections.

Removing a load-bearing wall

Steel beam and steel portal frame

For larger openings a single beam is not always sufficient. When the support is limited or when large forces must be transferred, a steel portal frame may be necessary.

A portal frame usually consists of:

We not only calculate the steel section, but also assess where the forces ultimately end up. A heavy HEB or HEA beam is of little value when the wall, floor or foundation it rests on has insufficient capacity.

Calculating a steel portal frame

Lintels and larger façade openings

Do you want to enlarge a window, door or sliding door? Then the existing lintel may be inadequate or need to be replaced entirely.

We can calculate structural provisions for:

Depending on the situation, a steel section, prefabricated concrete lintel or another structural solution can be chosen.

Stairwell opening or void in a floor

For a new staircase between two floors, part of the existing floor or timber joist layer often has to be removed. Existing floor joists may be interrupted in the process. The load must then be redirected to the remaining floor structure via new trimmer beams or other supporting structures.

Among other things, we assess:

On this basis we produce a structural drawing of the stairwell opening and the modified floor structure.

Stairwell structural calculation

Modifying or reinforcing a joist floor

In older homes, upper floors often consist of timber joist layers. During a renovation it may be necessary to check or reinforce the existing joist layer, for example when:

We assess the existing joist dimensions, timber quality, centre-to-centre spacing and span, and determine whether reinforcement is necessary. Possible solutions include, for example:

Structure for an extension

In an extension, various structural components come together. Think of:

That is why we prefer to assess an extension as one coherent structural system. A change to one component can affect another. A wide rear-façade opening, for example, causes considerable point loads at the columns, which must ultimately be absorbed by the floor and foundation.

Extension structural calculation

Foundation during a renovation

Not every renovation needs a new foundation. For extensions, larger portal frames, roof extensions or other interventions, however, a foundation check may be necessary.

Depending on the project, we investigate:

The starting point is always the same: the load must be safely transferred from the roof or floor above, through the load-bearing structure, ultimately down to the subsoil.

Foundation calculation

Roof extension and roof structure

A roof extension not only adds extra living space, but also extra weight to the existing building. Therefore, among other things, the following must be assessed:

In older homes it may be necessary to reinforce the existing structure locally. We can work out the structural components of the roof extension in full and coordinate them with the architectural drawings.

Roof extension structural calculation

Roof terrace and roof loading

An existing flat roof is not automatically suitable as a roof terrace. A roof designed solely as a roof may originally have been calculated for different loads than a floor on which people, furniture and other imposed loads are present.

Therefore we assess, among other things:

Where necessary, we design reinforcements.

Roof terrace structural calculation

From load to foundation

A structural calculation involves more than just determining a steel section. In every renovation we look at the full load path:

roof or floor above→ beam→ column or load-bearing wall→ floor / foundation beam→ foundation→ subsoil

It is precisely this coherence that matters. A steel beam may be strong enough on its own, while the masonry wall or existing foundation below it cannot readily absorb the concentrated load. That is why, where necessary, we look beyond the directly modified structural component alone.

Structural calculations and structural drawings

A sound structural design usually consists of two parts.

Structural calculation

The calculation records, among other things:

  • assumptions;
  • geometry;
  • material data;
  • loads;
  • load combinations;
  • forces and moments;
  • section check;
  • deflection;
  • support reactions;
  • connections;
  • foundation load, where relevant.

Structural drawing

On the drawing we indicate how the structure must be built. Depending on the project we show, for example:

  • position of steel beams;
  • steel sections;
  • columns;
  • supports;
  • base plates;
  • connections;
  • floor joists;
  • trimmer structures;
  • foundation beams;
  • reinforcement;
  • cross-sections and details.

This gives the contractor clear structural starting points for the execution.

Structural work for the building permit

When a building permit is required for your renovation, structural calculations and structural drawings can form part of the technical documents submitted for assessment.

Whether a permit, notification or other procedure is needed depends on the building plan and the location. This can be checked via the Dutch permit portal (Omgevingsloket). Even when a renovation may be carried out permit-free, the applicable technical building regulations still apply.

For the structural safety of existing buildings and renovations, the Dutch Building Decree (Bbl) refers to the NEN 8700 series. NEN 8701 contains the requirements for the loads applied to existing structures and renovations. The Eurocodes are additionally used within the Dutch framework for structural design.

ROMB can moreover combine the structural documents with:

Check the structure before the contractor starts

An important moment for structural advice is before load-bearing components are removed. When demolition is carried out first and only afterwards is it investigated how the structure works, unnecessary risks can arise.

In case of doubt, we therefore advise establishing before the work begins:

  1. which components are load-bearing;
  2. which load these components carry;
  3. which temporary support is needed;
  4. which permanent structure will be installed;
  5. how the forces are transferred.

This also gives the contractor clarity about materials, execution and planning.

Temporary support and propping plan

When removing a load-bearing wall or other load-bearing structure, temporary support may be necessary. The existing load must, after all, be supported before the permanent steel or concrete structure is fully functional. Depending on the situation, a propping plan may be required.

This looks, among other things, at:

The construction method must always be tailored to the actual situation on the building site.

Existing situation: first understand, then calculate

In renovations we almost always work with an existing structure. Therefore, where possible, we need information about:

When essential data is missing, additional investigation or an on-site survey may be necessary. We prefer not to rely on assumptions when a structurally important component can be checked on site.

Our approach

  1. You send the available information. Preferably we receive: the project address; architectural drawings; archive drawings; photos; approximate dimensions; a description of the intended renovation.
  2. We assess the structural intervention. We determine which components are being changed and which existing structural parts are affected as a result.
  3. Structural design. We choose a practical structural solution that fits within the existing home and the intended execution.
  4. Calculation and drawings. The required structural components are calculated and worked out on clear structural drawings.
  5. Coordination. Where necessary, we coordinate the documents with: the client; architect; contractor; steel fabricator; supplier; checking structural engineer; municipality.

Practical engineering

A structure does not need to become more complicated or heavier than technically necessary. When designing, we therefore look not only at strength, but also at practical feasibility.

Think, for example, of:

The result must be not only calculable, but also buildable.

One party for architectural and structural work

An advantage of ROMB is that architectural design and structural design can be coordinated within the same project. We can provide, among other things:

This way, architecture, structure and permit are not treated as separate parts.

For general building advice or projects outside our structural specialism, we work together with Aboss Bouwadvies.

Frequently asked questions about structural work in a renovation

Do I need a structural engineer for every renovation?

No. When only non-load-bearing components are changed, a structural calculation is often not needed. As soon as a load-bearing component is removed, changed or loaded more heavily, a structural assessment is important.

How do I know whether a wall is load-bearing?

Sometimes this can be deduced from original drawings or the structural build-up, but not always. The position, thickness, direction of the floor joists and the structure of the floors above must be assessed together.

Can a contractor decide themselves which steel beam is needed?

For a structurally sound design, the load must first be established. The length of the opening alone is insufficient to reliably determine a steel section.

Can I demolish first and calculate afterwards?

For load-bearing structures this is not advisable. First it must be clear how the existing structure is supported, both temporarily and permanently.

Do I need a calculation if my renovation is permit-free?

Permit-free does not mean regulation-free. Permit-free structures must also comply with the applicable technical building regulations.

Can you make only the calculation?

Yes. We can provide the structural part only, but if needed we can also combine building drawings, foundation calculations and permit guidance.

Can an existing steel beam be checked?

Yes. If the section, span, supports and relevant loads are known, we can assess whether an existing beam is suitable for the intended situation.

Do you also make drawings for the contractor?

Yes. In addition to the calculations, we can produce structural drawings and relevant details so the contractor or steel fabricator can build the structure.

Planning a structural change?

Is your contractor asking for a structural calculation? Do you want to remove a load-bearing wall, create a stairwell opening, or are you unsure whether the existing structure can carry your renovation?

Send us your drawings, photos and a short description of the desired situation. We will assess which structural work is needed and can then prepare a suitable quotation for the calculations and drawings.

Send your renovation plan