Caravans come in range of materials and structures. There are however, just two chassis types: the 'A'-frame chassis where rails taper out from the front to the axles and onto the rear corners. This frame supports a platform and body shell. The second type is the Rectangular Hollow Section (RHS) steel chassis which provides a complete frame for the body shell.

Aluminium frame

A most satisfactory caravan body. Aluminium tubing or extrusions are used for the framework, which is either riveted and/or welded together to form a skeletal frame for external aluminium cladding. This can be glued and/or riveted to the framework with styrene insulation, and a plywood lining is attached to the interior. This type of construction is light, strong, flexible and durable and it lasts for a long time.

Things to look out for: unsuitable grades of aluminium and/or incorrect welding techniques can cause frame cracking while the caravan is in use.

Timber frame

Timber frames are popular because they are easy to manufacture. This method can be either very good or very poor in relation to durability. Its success or otherwise depends on the type of timber chosen and the method of fastening timbers.

This type of body is usually made up of a timber framework with aluminium exterior sheeting, foam insulation and an interior lining of plywood.

Things to look out for: many timber-framed bodies have deteriorated due to the choice of timbers, glues and fasteners, eg staples. Water leaks in this type of caravan cause major damage and timber-work around doorways, windows, vents may rot and require extensive repairs.

When this type of van is incorrectly assembled it will not last, even with the best quality materials, particularly under rough road conditions. It is important to inspect exterior door, window and panel sealing regularly to ensure you find water leaks soon after they first happen.

Sandwich construction

With this type of construction a panel of exterior aluminium and interior timber ply sheet sandwich foam insulation material. The panel is bonded and is usually 20 to 25 mm thick.

Sandwich panels are used for caravan walls and windows, doors and other openings are cut out of the panel. This type of construction is considerably lighter than most and is quite durable when combined with a substantial chassis.

Fibreglass

With this construction, a timber or metal framework provides the basis for a fibreglass shell. Interior lining made from plywood or other suitable materials is attached to the basic body structure to form the interior walls and ceilings etc.

Things to look out for: while this type of body structure is quite durable, these bodies can be quite heavy and are subject to cracking when considerable body movement is experienced, eg on rough road surfaces.

Steel frame

This is where light Rectangular Hollow Section (RHS) steel tubing is welded to form a framework onto which an aluminium exterior cladding is fastened with foam or styrene insulation. The body interior walls are made of plywood.

This type of construction is usually very sturdy as long as the right materials are used with correct welding procedures. With adequate corrosion protection, this kind of van will give durable service.

Things to look out for: the major problems with this type of construction are excessive weight and corrosion over longer periods.