Brick Extension vs HUP Extension: What Is the Difference?

The main difference between a brick extension and a hup! extension is the construction of the walls and roof. A traditional extension is built layer by layer on site from bricks, blocks, insulation and mortar. A hup! extension is a modular system: factory-made components are delivered and assembled on site. Both need sound foundations, both must comply with Building Regulations, and both can look like a conventional extension once finished.

We build both at Complete Property Solutions, so this guide is a fair comparison rather than a sales pitch. It is written for homeowners across Warrington, St Helens, Wigan and the wider North West who are weighing up the two routes.

TL;DR

• Brick-and-block is built wet, on site, course by course. hup! is a factory-made system assembled on site.
• hup! walls are thinner (215mm) than a typical insulated cavity wall, which can give you a little more usable floor space.
• hup! can be finished in brick slips or render, so appearance alone does not tell you how an extension was built.
• Both options need suitable foundations, Building Regulations approval, and planning permission only where your project requires it.
• The right choice depends on your site, your design, your house style and your priorities. We can talk you through both at a site visit.

Table of Contents

• How each type of extension is built
• Brick extension vs hup! extension at a glance
• Insulation and thermal performance
• Design flexibility
• Usable floor space
• Finishes: why appearance does not identify the build
• Disruption and timescales
• Foundations: both options need them
• Building Regulations and planning permission
• What affects the cost
• When each option may suit you
• Our view as a family-run builder
• Talk to us about both options
• FAQs
• Arrange a site visit
• Sources

How each type of extension is built

Traditional brick-and-block

A traditional extension uses an outer skin of brick, a cavity with insulation, and an inner skin of blockwork, topped with a timber or steel-supported roof. Which? describes traditional extensions as built using materials such as concrete, bricks and wood. Bricklayers build the walls up course by course, which means the work is exposed to the weather and the walls need time to cure before the next trades follow.

It is the method most builders and most surveyors know best. It is flexible, easy to adapt on site, and the finished result is what many homeowners picture when they think of a house extension.

The hup! building system

hup! is a modular building system made by Ultraframe. Which? explains that its factory-made components are delivered and assembled on site. Rather than building up a cavity wall in stages, the installer fits a pre-engineered wall and roof system onto a prepared base. The wall panels are designed to take a choice of external finishes, which we cover below.

As an approved hup! Building System partner, we are trained in fitting the system and know where it works well and where a conventional build is the better answer. You can read our own overview in hup! extensions explained: are they worth it?.

Brick extension vs hup! extension at a glance

Insulation and thermal performance

Both methods can meet current Building Regulations. The difference is how they get there.

Ultraframe’s own figures say hup! walls achieve a U-value of 0.17 W/m²K, against the 0.18 W/m²K wall target it cites for Building Regulations. A U-value measures how quickly heat passes through a wall, so lower is better. These are manufacturer figures for the wall system, and the real performance of your finished extension also depends on the roof, glazing, floor, airtightness and how well everything is installed.

A brick-and-block wall can reach the same target by adding more insulation, which makes the wall deeper. The same Ultraframe page says a cavity wall grows from 300mm to 350mm to reach 0.18 W/m²K, with more thickness added by internal dot-and-dab plasterboard.

We would not tell any homeowner that one method is automatically warmer than the other. A well-built brick extension with good insulation and quality glazing will perform extremely well. What matters is the design, the detailing and the standard of workmanship.

Design flexibility

This is where brick-and-block has a natural edge. Because it is built by hand on site, a bricklayer can adapt to awkward corners, unusual roof lines, curved features or a matching detail on a period property.

hup! offers a good range of layouts, including lean-to, tiled roof and glazed roof options, single-storey extensions and conservatory conversions. Which? notes that hup! covers single-storey builds and conservatory conversions. If you want a two-storey extension, a complex shape, or a wraparound with several changes of level, we will often recommend traditional construction.

If your plan is a clean, rectangular single-storey room such as a kitchen-diner, family room or garden room, hup! is often a strong fit. Our kitchen extensions team can show you both routes for the same layout.

Usable floor space

A thinner wall means more room inside. hup! walls are 215mm wide, compared with the 300mm of a cavity wall built to the same U-value, according to Ultraframe’s published figures. Over a whole room that can be a modest but useful gain.

Here is a simple worked example. If the difference in wall thickness is around 100mm and your extension has walls on three sides, you gain roughly 100mm of internal width on each. In a small kitchen extension, that could be enough to fit a slightly wider run of units or a larger island. It will not transform a room, but on a tight plot it is worth knowing about.

The flip side: if you are limited on the outside by a boundary or by permitted development limits, a thinner wall helps inside. If the footprint is not constrained, the difference matters less.

Finishes: why appearance does not identify the build

Many people assume a hup! extension looks different from a brick one. Often it does not. hup! can be finished with brick slips, render or cladding. Ultraframe’s specification guide shows brick slips and render as wall finish options, and says the system is compatible with other wall finishes available on the market.

Brick slips are thin slices of real brick fixed to the wall panel. Once pointed, they can closely match your existing home. So when you see a neat brick extension on a street in Great Sankey or Culcheth, you cannot tell by looking whether it is brick-and-block or a hup! build with brick slips.

This matters in practice:

• If your house is a mid-century brick semi in Lowton or Haydock, you can match the brick colour with either method.
• If you prefer a rendered or contrasting look, both work.
• Ask any builder how the wall is actually built, not just what it looks like.

Disruption and timescales

We do not quote speed claims we cannot stand behind, so here is the careful version. Which? says modular building is typically faster and less disruptive than a traditional extension, and notes that hup! claims its system is five times faster to build. That is a manufacturer claim about the build itself, so treat it as a guide rather than a promise for your whole project.

The building phase is only part of the overall timeline. A realistic project includes:

1. Design and drawings.
2. Planning or a lawful development check, if needed.
3. Building Regulations submission.
4. Groundworks and base.
5. Walls and roof (this is the stage where hup! can save time).
6. Electrics, plumbing, plastering or internal finishing, flooring and decoration.

With hup! the structure can be weathertight sooner, which can reduce the time your home feels like a building site. With brick-and-block, the wet trades and curing time usually add to the on-site period. Either way, kitchen fit-outs, glazing lead times and inspections will shape the final timetable. We give you a programme at quotation stage so you know what to expect.

Foundations: both options need them

A common myth is that hup! needs no foundations. It does need a suitable base. Ultraframe’s technical guide says hup! can be installed on an existing foundation if it provides a level surface, but the correct base type and depth still depend on ground conditions and Building Regulations.

Ultraframe also says the hup! Base can use concrete pads or ground screws rather than full foundations, which means less excavation and concrete. Its specification guide adds that conventional strip foundations can also be used. In Warrington and St Helens, where ground conditions vary, we assess each site before recommending a base. Clay, nearby trees and old drains can all change the answer, for brick and hup! alike.

Building Regulations and planning permission

Both extension types must comply with Building Regulations. That approval is separate from planning permission, and as one council’s homeowner guide puts it, all extension and conversion projects need it. Regulations cover structure, insulation, ventilation, drainage, fire safety and electrics, and a building control officer inspects at set stages.

Planning is different. Which? says hup! extensions are subject to the same planning requirements as any other extension or conservatory. In England, enlarging a house is permitted development only if it meets the limits and conditions in Class A of the General Permitted Development Order. Whether you need an application depends on your house, your plot, and the size and position of the extension, not on the construction method.

For more detail, see our guides to permitted development for house extensions and permitted development vs planning permission.

What affects the cost

There is no honest single price for either option, because the cost depends on the project. Which? gives a guide for traditional builds: from around £30,000 for a small single-storey extension to £120,000 or more for a large two-storey one. It does not publish a comparable hup! price, and says hup! pricing varies with size, customisation and whether an existing base and foundations can be reused.

The factors that move the figure most are:

• Size and number of storeys. Bigger and taller costs more.
• Groundworks. Poor ground, drainage runs or trees can add to the base cost.
• Roof type. Solid tiled, glazed and flat roofs are priced differently.
• Glazing. Bi-folding doors, aluminium patio doors and rooflights add cost.
• Finishes. Brick slips, render or full brick, plus flooring and decoration.
• Internal work. Kitchen, electrics, underfloor heating and plastering.
• Structural alterations. Opening up the old rear wall with an RSJ, for example.

If hup! can reuse an existing base, such as a sound conservatory base, there may be savings. If it cannot, the gap between the two methods can be small. For a deeper look at why numbers differ, read why extension quotes vary so much and our house extension cost guide.

When each option may suit you

Brick-and-block may suit you if

• You want a two-storey extension or a more complex shape.
• Your home is period or has distinctive brickwork and detailing to match.
• You are combining the extension with major structural alterations.
• The design needs on-site adaptability, such as a sloping plot.

hup! may suit you if

• You want a single-storey room, garden room or kitchen-diner.
• You are replacing an old conservatory and its base is in good condition.
• You want to keep the on-site build period shorter.
• You want to make the most of the floor area inside a fixed footprint.

Either may suit you if

• You want a brick-slip finish that matches your home.
• You want a high standard of insulation and glazing.
• You value fixed-price quotes and clear project management.

Our view as a family-run builder

We have been building for more than 35 years, and we have seen methods come and go. What has not changed is that the build quality on the day matters more than the label on the system. A poorly detailed brick wall and a poorly installed modular wall will both let you down.

We are members of the Guild of Master Craftsmen and an approved hup! Building System partner, so we are not tied to one answer. When we visit a home in Rainhill or Penketh, we look at the ground, the existing house, the garden access and how you live, and then we show you what each route would mean for your design and your budget. Some customers choose brick, some choose hup!, and some start out sure of one and change their mind after seeing the plans side by side.

Our advice is simple: ask for both options priced on the same drawings, and compare them like for like.

— Gareth

Talk to us about both options

We design and build house extensions, kitchen extensions, garden rooms, garage conversions and structural alterations, and we manage the project from design to completion on a fixed-price basis. If hup! is on your shortlist, see our hup! extensions and garden rooms page. If you would rather compare it with traditional construction, our house extensions page covers single-storey, double-storey and wraparound builds.

We work across Warrington, St Helens, Wigan, Culcheth, Golborne, Ormskirk, Southport and nearby areas. If you are still choosing a company, our homeowner checklist for choosing extension builders explains what to ask.

FAQs

Is a hup! extension cheaper than brick?

Not automatically. Price depends on size, design, roof, glazing and groundworks. Which? says hup! pricing varies with customisation and whether an existing base can be reused, and it does not publish a direct price comparison. The fairest approach is to have both methods quoted on the same plans.

Is a hup! extension any good?

It can be an excellent option for the right project. Which? reports that hup! builds are certified to last at least 60 years and are typically faster and less disruptive than traditional extensions. As with any extension, quality of installation and design is what decides the result.

Do hup! extensions need foundations?

Yes, they need a suitable base. That could be an existing foundation with a level surface, concrete pads, ground screws or conventional foundations, depending on your site and Building Regulations. A site survey will confirm which applies.

Do I need planning permission for a hup! extension?

The same rules apply as for a brick extension. Many single-storey extensions can be built under permitted development if they meet the limits, but that depends on your property and plot. Building Regulations approval is needed either way.

Can you tell a hup! extension from brick by looking?

Often not. hup! can be finished in brick slips or render, so a finished extension can look just like a brick-built one. Ask how the walls are constructed rather than judging by appearance.

Arrange a site visit

The quickest way to settle brick versus hup! is to have someone look at your house and garden. Get in touch with Complete Property Solutions to arrange a site visit, and we will talk through both options, show you the differences on your own plans and give you a clear fixed-price quotation.

Sources

• Home extensions: traditional vs modular building vs annexe, Which?
• hup! walls, Ultraframe Trade
• hup! Base, Ultraframe Trade
• hup! technical guide, Ultraframe
• hup! specification guide, Ultraframe
• Extensions: a homeowner’s guide, Epping Forest District Council
• The Town and Country Planning (General Permitted Development) Order, Schedule 2

Recommended

• What Makes a Good Extension and How to Choose the Right Builder
• Why do extension quotes vary so much?
• How home extension planning works: a UK guide
• Hup! extensions explained: are they worth it?