What Drawings Are Needed?

Planning drawings are not normally enough for construction.

A Building Regulations drawing package develops the preferred design into a more detailed technical proposal.

Depending on the project, the package may include:
 

• Proposed floor plans

• Detailed dimensions

• Foundation details

• Wall construction

• Floor build-ups

• Roof details

• Insulation specifications

• Drainage layouts

• Ventilation information

• Fire-safety notes

• Window and door details

• Rooflight or roof-lantern details

• Structural references

• Construction notes

• Material specifications
   

Structural calculations are normally prepared separately by a structural engineer.

The designer and structural engineer should coordinate their information so that the builder receives a clear and consistent package.

 

Why Prepare Detailed Drawings Before Asking Builders to Quote?

A builder may be able to provide an early budget estimate from planning drawings.

However, a detailed quotation usually requires more information.

Without technical drawings and structural calculations, builders may make different assumptions about:
 

• Foundations

• Drainage

• Steel beams

• Insulation

• Roof construction

• Glazing

• Electrical work

• Plumbing

• Finishes
   

This makes quotations difficult to compare.

One builder may include the necessary structural work. Another may leave it out and add it later as an extra.

A clear Building Regulations package helps reduce uncertainty and gives builders a stronger basis for pricing the same project.

 

Full Plans Application

For most house extensions, a full-plans application is the most suitable route.
 

Detailed drawings and supporting information are submitted for review.
 

The plans are checked before the project progresses too far, allowing technical issues to be identified earlier.
 

A full-plans application can provide:
 

• Greater clarity before construction begins

• A reviewed set of technical drawings

• A clearer basis for builder quotations

• Reduced risk of avoidable changes on site

• Better coordination with the structural engineer

• A more organised construction process
   

For a substantial extension, this is usually preferable to relying on limited information and resolving the technical design during the build.

 

Building Notice

A building notice may be available for some smaller domestic projects.
 

This route allows work to begin without detailed plans being formally approved in advance in the same way as a full-plans application.
 

The work must still comply with the Building Regulations.
 

A building notice may be suitable for a straightforward alteration where the construction is simple and the builder is experienced.
 

However, for a larger extension involving structural work, drainage changes or a more complex design, the full-plans route is often more sensible.

 

Who Approves the Work?

For a typical domestic extension in England, building control approval can normally be dealt with through:
 

• The local authority Building Control department

• A private registered building control approver
   

The chosen building control body will review the relevant information and inspect the work at appropriate stages.
 

Building Control should not be confused with the builder, designer or structural engineer.
 

Each has a different role.

 

What Site Inspections Are Required?

Building Control will normally inspect the project at several stages.
 

The precise sequence will depend on the work, but inspections may include:
 

• Excavation before foundations are poured

• Foundations

• Drainage before it is covered

• Ground-floor construction

• Damp-proof course

• Structural steelwork

• Roof construction

• Insulation

• Fire-safety measures

• Completion

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Important work should not be covered before the relevant inspection has taken place.
 

The builder should coordinate the inspection programme and make sure the building control body is notified at the correct stages.

 

Do I Need a Structural Engineer?

Many house extensions require structural engineering input.

This is particularly likely where the work involves a large opening between the original house and the extension.

A structural engineer may also be needed for:
 

• Steel beams

• Columns

• Padstones

• Roof alterations

• Double-storey extensions

• Foundation design

• Chimney-breast removal

• Internal wall removals

• Temporary support

• Complex drainage or ground conditions

The structural calculations form an important part of the technical package and help the builder price the work more accurately.

 

Can Work Start Before the Technical Details Are Finalised?

It may be possible to begin some work before every technical detail has been agreed.
 

However, rushing into construction can create avoidable risk.
 

For example:
 

• The foundations may need to be deeper than expected

• A drain may need to be moved

• The steel beams may need to change

• The insulation design may be inadequate

• The proposed glazing area may be excessive

• The roof detail may require revision
   

Resolving these issues on paper is usually easier and cheaper than redesigning the extension after work has started.

 

What Happens When the Work Is Complete?

Once the extension has been completed and the necessary inspections have taken place, the building control body should issue the relevant completion certificate where the work complies.
 

Keep this document safely.
 

It may be important when selling or remortgaging the property.
 

A completion certificate provides evidence that the work has passed through the Building Control process.

 

What If Building Regulations Approval Was Not Obtained?

Building work carried out without the correct Building Regulations process can create difficulties later.
 

Potential problems may include:
 

• Questions from solicitors

• Problems when selling the property

• Mortgage-lender concerns

• The need to expose completed work for inspection

• Remedial work

• Additional professional fees

• Delays

• Enforcement action
   

Retrospective regularisation may be possible in some circumstances, but it is not the preferred route for a new extension.
 

The best approach is to deal with Building Regulations properly before work begins.

 

Building Regulations Approval Does Not Replace Other Permissions

Building Regulations approval is only one part of the project.
 

Depending on the property and the proposed work, you may also need:
 

• Planning permission

• Confirmation of permitted development rights

• A Lawful Development Certificate

• Structural calculations

• Party Wall notices

• A Party Wall Award

• A build-over agreement

• Freeholder consent

• Leaseholder consent

• Listed-building consent

• Conservation-area advice
   

Each issue should be checked separately.

 

Prepare Properly Before You Build

A successful extension requires more than an attractive layout.
 

The design, construction details, structural calculations, drainage arrangements, insulation and Building Control process all need to work together.
 

Preparing a proper technical package can help builders quote more accurately, reduce uncertainty on site and give the project a much stronger foundation from the outset.

 

Find Suitable Extension Professionals

Depending on your project, you may need architectural design support, Building Regulations drawings, structural calculations, Building Control input, Party Wall advice and an experienced extension builder.
 

Tell us a little about your home, the extension you are considering and the stage you have reached. We can help connect you with suitable professionals for the next steps.