Building a DIY fire pit
A basic garden fire pit can be built quickly and easily. In fact if you buy a standard fire pit kit (i.e. one with no hard landscaping or seating) you should be able to set it out and assemble it in less than a day.
The project
A basic fire pit is really nothing more than a circular hole in the ground with a solid base and a low level wall encircling it. You place wood or coal in the pit, ignite it, and sit back and enjoy the warmth. You can even use it as a barbeque. Consequently, digging out and building a fire pit is not rocket science and it requires a minimum of DIY skill.
The dimensions
The fire pit hole is usually circular with a diameter of a minimum of 18 inches, but generally between 2 feet and 3 fee is better. You can of course build a square pit, or one of any other geometric shape, but it will be more complex to construct.
The finished level of the base of the pit should be between 6 inches and one foot below the surrounding ground level. This means that it is necessary to excavate to a greater depth than this to allow for the fire pit base.
The fire pit's encircling wall will be between 12 and 18 inches in height and the stone or brick used should be at least 4 inches wide. Higher walls will prevent the pit from sucking in the air needed to burn the fuel.
Any seating placed around the fire pit should be at least 4 feet from the fire pit walls.
The construction
The fire pit should be located a safe distance from buildings and vegetation in an area that is flat and well drained.
The fire pit shape can be marked on the ground using sand as a template for the excavation (digging) which can be done with a spade (and a pick if the ground is rocky).
The pit base should be composed of a minimum of 6 inches of concrete. A thicker base will be harder wearing and 6 inches of compacted hardcore (crushed stone) topped with 6 inches of concrete is ideal. This would require a total dig depth of between 18 inches and 2 feet.
Most fire pit walls require a solid flat and level base, so it is a good idea to use the fire pit base as a footing for the encircling wall. This means that you need to increase the diameter of the pit base by X2 the width of the wall. This will also make the completed fire pit look more permanent as the walls will emerge from the ground rather than sitting on top of it.
When the fire pit base is excavated and constructed the fire pit wall can be built. The wall can be dry-laid (without mortar), or wet-laid with mortar joint beds and perpends between the horizontal and vertical intersections of the masonry units. The stone, bricks or blocks used to build the wall should be bonded (i.e. have their joints staggered for extra strength and stability). This also looks better.
If the fire pit wall is wet-laid, then a vertical layer of mortar can be used to line the internal surface of the wall. This will aid cleaning and prevent blow-through of ash, sparks etc.
The extras
Most fire pit projects use paving slabs, cobbles or brick sets to create a hard landscaped patio area around the fire pit. This can be done as part of the original project, or as a secondary project at some point in the future and it allows patio furniture to be sited around the fire pit.
Permanent stone or brick seating can be built around the fire pit, usually by using the same style of stones or bricks used to make the pit itself. Even basic seating like flat stone benches can look good and help to create an all year round outdoor partying and eating environment.
Fire pits are particularly appealing at night and since they can double up as barbeques they make great entertaining center points in a garden.