How to Build a Brick Garden Barbecue: From the Foundation to the Chimney

Building a brick garden barbecue may seem like a relatively straightforward project: a stable foundation, several courses of masonry, a firebox, a chimney and a worktop. In practice, however, a successful result depends on how well all these elements work together.

The foundation must support the considerable weight of the structure. The firebox must withstand repeated heating and cooling. The chimney must draw the smoke upwards instead of directing it back towards the person cooking. The materials around the fire must be suitable for high temperatures, while the external surfaces must withstand rain, snow and freezing conditions.

At Raimar, we have been manufacturing modular garden barbecues in Kresna for more than 30 years. In this article, we look at the main stages of building a barbecue from scratch, the important decisions to make before starting and the mistakes that may make it difficult to use later.

This guide is intended to provide practical information, but it does not replace a structural design. For a large barbecue, heavy natural stone cladding, a roofed structure or a barbecue connected to an existing building, you should consult a structural engineer or an experienced contractor.

Decide how you will use the barbecue before you start building

The first step is not excavation. It is clearly defining the functions you want the barbecue area to have.

Consider whether you want only a charcoal grill or a complete outdoor cooking area with:

• a preparation worktop;

• storage space for wood and charcoal;

• an outdoor sink;

• a wood-fired oven;

• cupboards or open shelves;

• a dining table;

• a roof or pergola.

A small family barbecue requires a different amount of space from a structure intended for large gatherings or commercial use.

It is good practice to select the cooking grate or metal grill frame at this stage. The dimensions of the firebox should be based on the actual accessory you will use, rather than on an approximate idea of how large the grate should be.

You should also plan for possible future expansion. Many outdoor cooking areas begin with a single stone barbecue, with a worktop, sink and oven being added later.

How to choose the location

The location affects safety, convenience and the way the smoke moves.

The barbecue should be positioned at a practical distance from the kitchen. If it is too far away, cooking will involve constantly carrying food, dishes and water back and forth. If it is too close to the house, smoke and heat may cause discomfort.

When selecting the location, check:

• whether the ground is stable and level;

• the direction of the prevailing wind;

• whether there are trees, branches or easily flammable materials nearby;

• whether smoke may reach windows, terraces or neighbouring properties;

• whether there is enough working space in front of the firebox;

• whether water and electricity can be supplied to the area;

• whether there is room for a future worktop, sink or oven.

Do not build the barbecue in an enclosed or poorly ventilated area. If it will be positioned under a roof, the smoke extraction, chimney height, fire safety measures and distances from the roof structure must be considered in advance.

Do not assume that a taller chimney will automatically solve every smoke problem. Chimney performance also depends on the flue cross-section, the shape of the smoke chamber, the size of the firebox opening and the air currents around the structure.

Planning the dimensions

There is no single universal size for a garden barbecue.

The dimensions should be determined according to:

• the selected cooking grate;

• the number of people you usually cook for;

• the available space;

• the height of the person who will use the barbecue;

• the presence of a worktop and additional modules;

• whether it will be used for charcoal, an electric grill or both;

• the overall design of the firebox and chimney.

The working height should allow food to be placed and turned comfortably without the user having to bend down continuously.

There should be enough space in front of the firebox for safe and comfortable use. Do not position the dining table and seating immediately behind the person cooking, as this restricts movement and creates a risk when handling hot cookware.

Before construction begins, mark the outline of the future structure on the ground. You can temporarily arrange bricks or mark the dimensions with chalk and string. This will help you assess the actual scale of the barbecue and the space available for movement.

What type of foundation does a masonry barbecue need?

A stone or brick barbecue is a heavy, permanent structure. It should therefore not be built directly on grass, topsoil or unprepared ground.

An unstable foundation may lead to:

• uneven settlement;

• tilting of the structure;

• cracks in the joints;

• movement of individual sections;

• problems between the firebox and chimney;

• water collecting around the base.

A typical solution involves removing the unstable top layer of soil, preparing a compacted mineral base and casting a reinforced concrete slab.

The exact thickness and reinforcement of the slab should not be determined using a universal diagram found online. They depend on the size and weight of the barbecue, the type of soil, the local climate and whether the project includes additional modules or a roof.

The foundation must be:

• flat;

• level;

• capable of supporting the required load;

• wider than the barbecue itself;

• protected against permanent water accumulation;

• fully stabilised before construction continues.

Drainage around the barbecue should also be considered. Even a well-constructed slab will not help if the surrounding area regularly fills with standing water.

Do not load freshly poured concrete simply because its surface appears dry. The time required for it to achieve sufficient strength depends on the concrete mixture, slab thickness, temperature and installation conditions.

Which materials can be used for the main structure?

The external load-bearing structure of a garden barbecue can be built from various masonry or concrete materials. However, not every material is suitable for direct contact with fire.

Depending on the design, the main structure may be built from:

• fire-resistant ceramic or fireclay bricks;

• concrete blocks;

• reinforced concrete components;

• a combination of masonry and concrete;

• natural stone, provided that the structure is correctly designed.

The materials used for the outer structure and those used for the firebox should not be treated as interchangeable.

Standard bricks and cement-based mortar may form part of the external structure, but the area exposed directly to flames and high temperatures must be made from suitable refractory materials.

Do not use aerated concrete blocks as an unprotected internal surface of the firebox. They are not intended for continuous direct exposure to fire.

Building the base and lower section

Once the concrete foundation has achieved the required stability, the precise position of the walls should be marked on it.

The first course is critical to the entire structure. It must be checked:

• horizontally;

• vertically;

• across the diagonals;

• in relation to the main axis of the barbecue.

Even a small deviation at the beginning will increase with every subsequent course and may make the construction of the firebox and chimney more difficult.

The lower section is often designed as an open storage area for wood or charcoal. Its design must maintain sufficient load-bearing capacity for the slab and firebox above it.

Do not leave an excessively wide opening without suitable reinforcement. The upper slab must support not only its own weight but also the firebox, walls and part of the chimney.

The slab beneath the firebox

A load-bearing slab is constructed above the lower section to support the firebox.

This is one of the elements where improvisation can lead to serious problems. The slab must support the permanent weight of the firebox and withstand repeated temperature cycles.

The required dimensions, reinforcement and temporary support should be determined according to the specific structure. For a wider barbecue or a combined project with an oven and worktops, it is advisable to have this part checked by a structural engineer.

The slab must be carefully levelled. Any unevenness should not later be compensated for with an excessively thick layer of refractory mortar.

How to build the firebox

The firebox is the area exposed to the greatest thermal stress.

It should be constructed from refractory or fireclay bricks, bonded with mortar or adhesive designed for high temperatures. Standard cement-based tile adhesive is not suitable for the inside of the firebox.

The design should include:

• a level base for the embers;

• side and rear walls made from refractory materials;

• a stable support for the cooking grate;

• access for removing ash;

• an adequate air supply;

• a transition to the smoke chamber.

It is useful to provide more than one height for the cooking grate. This allows the distance between the food and the embers to be adjusted according to the type of food and the intensity of the heat.

The refractory inner lining and the external structure expand differently when heated. They should therefore not be connected in a way that prevents normal thermal movement.

The exact solution depends on the system being used and should follow the instructions provided by the manufacturer of the refractory bricks and mortar.

The smoke chamber and chimney

The chimney is one of the most difficult parts of building a garden barbecue.

Smoke problems are not always caused only by insufficient chimney height. Other possible causes include:

• an excessively large firebox opening;

• an undersized flue;

• an abrupt or incorrectly shaped transition;

• a chimney that is too low;

• an obstruction near the chimney outlet;

• strong air currents;

• an insufficient air supply to the fire.

A smoke chamber is formed above the firebox to direct the smoke gradually towards the flue. The transition should not be arbitrary or excessively abrupt.

The chimney should be vertical, stable and protected against water penetration. When the barbecue is positioned close to a wall or beneath a roof, its design requires additional attention.

There is no single reliable chimney formula that will work for every barbecue. The size of the firebox opening, the chimney height and the flue cross-section must be considered as parts of a single system.

For this reason, the chimney is often the part of the project for which it is most worthwhile to use an experienced contractor.

Worktop and food preparation area

Even a small worktop next to the barbecue makes outdoor cooking considerably easier.

It can be used for:

• food waiting to be cooked;

• chopping boards and knives;

• herbs and seasonings;

• cookware;

• cooked food;

• barbecue utensils.

The worktop should be suitable for outdoor conditions and easy to clean. Natural stone is a good option when it has been correctly processed and impregnated.

Different types of stone react differently to grease, acids and freezing temperatures. The material and surface finish should therefore be selected according to the specific application.

When installing a stone worktop, provide a slight outward slope for drainage and avoid areas where water can collect permanently.

Natural stone cladding

The cladding gives the barbecue its finished appearance and connects it visually with the paving, façade and other materials used in the garden.

Suitable options include:

• irregular gneiss slabs;

• cut stone strips;

• limestone;

• travertine;

• marble with a suitable outdoor finish;

• other natural stone cladding suitable for exterior use.

The substrate must be solid, clean and properly prepared for bonding. The adhesive and grout must be suitable for both natural stone and outdoor use.

The stone around the firebox does not replace the refractory bricks. The decorative cladding and the firebox perform different functions.

Once installation is complete and the materials have dried fully, the stone can be impregnated. This limits the absorption of water, grease and other contaminants.

Does the barbecue need a roof?

A roof allows the area to be used in rain or strong sunshine, but it also makes the project more complex.

Simply placing a wooden shelter above the barbecue is not sufficient.

The design must take into account:

• the distance from combustible materials;

• the route of the chimney;

• protection around the opening in the roof;

• ventilation;

• the height of the structure;

• rainwater drainage;

• local construction and fire safety requirements.

For a wooden pergola or roof, always obtain a professional solution for the area around the chimney.

Drying and the first fire

After the masonry work has been completed, the structure must be allowed to dry.

The exact drying time depends on the materials used, the thickness of the joints, the weather conditions and the manufacturers’ instructions. Do not light a strong fire immediately after construction simply because the outer surface appears dry.

The first fires should be gradual:

1. Start with a small quantity of dry kindling.

2. Maintain a moderate fire.

3. Allow the structure to heat up gradually.

4. Avoid blowtorches and flammable liquids.

5. Do not cool the hot firebox with a large quantity of water.

Gradual heating helps the remaining moisture escape and reduces sudden thermal stress in the materials.

Small surface cracks may appear as a result of thermal expansion. They should be monitored, but not every fine crack indicates a structural problem.

The most common mistakes when building a brick barbecue

Building directly on the ground

The weight of the structure requires a stable foundation. Soil that appears firm may change after heavy rainfall, freezing or prolonged dry weather.

Using standard materials inside the firebox

Standard bricks, adhesives and mortars are not automatically suitable for direct contact with flames and high temperatures.

Choosing the dimensions before selecting the cooking grate

When the grate is purchased at the end of the project, the supports often have to be modified or a non-standard accessory must be used.

Designing the chimney only for appearance

An attractive chimney does not guarantee effective smoke extraction. The cross-section, transition and height must work together.

Leaving insufficient space around the firebox

The person cooking needs enough room to move, place cookware down and step safely away from the fire.

Lighting an excessively strong first fire

Residual moisture and rapid heating increase the risk of cracks and materials becoming detached.

Adding a roof without a chimney solution

A wooden shelter and a hot flue create a dangerous combination when they have not been designed correctly.

Building from scratch or choosing a ready-made modular barbecue

Building a brick barbecue from scratch is suitable for people who want a completely individual design and have the necessary skills, time or a trusted contractor.

The project involves several separate stages:

• preparation and concreting of the foundation;

• waiting for the required curing periods;

• construction of the load-bearing structure;

• installation of a reinforced slab;

• construction of a refractory firebox;

• construction of the smoke chamber and chimney;

• installation of the worktop;

• installation of the cladding;

• drying and gradual first firing.

The alternative is a ready-made masonry barbecue. With this option, the main structure, firebox, smoke extraction system and natural stone cladding are manufactured in advance as compatible components.

The barbecue is delivered on a pallet as separate, numbered panels. A stable and level installation area must be prepared on site, after which the components are assembled according to the supplied diagram.

The main differences

In both cases, a stable and level foundation is essential.

How a ready-made Raimar barbecue is assembled

Installing a ready-made barbecue is different from constructing a brick structure from scratch.

The components are arranged according to the numbering in the supplied assembly diagram. Before bonding, the contact surfaces are washed and thoroughly moistened with water.

An even layer of C2 cement-based adhesive is applied along the entire edge to create full contact without voids. The panels are pressed together and temporarily secured with a strap, wire or wrapping film.

The horizontal and vertical alignment is checked at every stage. Once the structure has been assembled, the visible joints are filled and the surfaces are cleaned.

Assembly itself usually takes several hours, depending on the size of the model and the number of people involved. Before the first fire is lit, the adhesive must be allowed to dry completely—usually for one to two days, depending on the season and conditions.

This is the main difference: a ready-made barbecue still requires a stable installation area, but it eliminates the need to design and build the main structure, firebox, smoke extraction system and natural stone cladding separately.

Which solution is suitable for your garden?

Choose to build from scratch when:

• you require completely individual dimensions;

• the project must follow a specific architectural design;

• you have an experienced contractor;

• you accept a longer construction process;

• you want to participate personally in every stage.

A ready-made barbecue is more suitable when:

• you want a clearly defined model and size, with a clear idea of the final result;

• you prefer to minimise construction work in the garden;

• you want a ready-made firebox and chimney;

• you want natural stone cladding;

• you prefer installation according to an assembly diagram;

• you plan to add a worktop, sink or oven later.

There is no universally correct choice. The important thing is to understand in advance the skills, materials and time required to build a barbecue from scratch, as well as what has already been prepared for you when choosing a ready-made modular model.

Browse our ready-made garden barbecues, manufactured in Kresna from reinforced concrete panels, with a refractory firebox and natural stone cladding.

For more information about durability, use and possible combinations, read our article “Why Choose a Masonry Stone Barbecue for Your Garden”.

This article was prepared with the expert contribution of Eng. Rayko Smilyanov, a structural engineer with extensive manufacturing experience in natural stone and garden products at Raimar.