Lightweight steel construction because of its appearance, construction progress fast, environmentally friendly and integrated low cost advantages, rapid development, has been widely used in the construction industry. The light steel building envelope system as an integral part of the lightweight steel construction, its quality directly affects the entire light steel construction quality is good or bad. It comprises two main wall systems and roofing systems.

1）the wall system constructed of lightweight steel construction 

1.1 wall design requirements. In the structure of the wall system, wall design is critical in the design must meet the following requirements: 

First, the wall should have a certain strength, rigidity and stability requirements. 

Secondly, the wall must have good thermal insulation function. 

Than the last, the wall in addition to meeting the basic functional requirements, but also should have some noise function, which should meet the requirements for sound insulation aspects; fire prevention, fire safety regulations should be consistent with the corresponding combustion performance and fire resistance requirements; in choice of material of the wall, should use lightweight materials, while also considering proof, waterproof, windproof and anti-freeze and economy requirements.1.2 Structural design wall system 

Wall system configuration consists of many aspects of composition, and structure during the design of the wall system, the key point is the wall structure and node layout practices of these two aspects, the following focuses on the structural arrangement and node wallboard practice these two aspects of the design . 

1.2.1 wallboard structural arrangement. Between the use of polyurethane sandwich panels wall socket type connection, the connection between plate and wall frame structure should be equipped with special fixtures. To meet the different architectural styles of the pursuit, wall plates can be stacked vertically and horizontally using two kinds of layout patterns. The heel plate is a plate in the longitudinal direction perpendicular to the ground arrangement, a traditional light steel building practices. Plate horizontally is a longitudinal direction of the plate arrangement parallel to the ground, is a new approach light steel building, the effect of relatively new building facade, wall shelf systems are all vertical layout, the load-bearing steel columns and wall bracket together constitute , a variety of load bearing walls are borne by the steel and wall shelves. 

1.2.2 node approach. When building wall using upright principles, all parts of the building node (baseboards, door and window openings, etc.) are more mature approach. The building wall plate horizontally approach adopted in the actual project is still relatively small, according to engineering practice, general reference node structure except the traditional approach, the structure baseboards, door and window openings and parapet around the top of peer nodes, and the traditional approach differ.

1.3 Wall commonly used materials 

Currently, the domestic species as a light sheet wall envelope more, there are pre-painted metal pressure plate sandwich panels, steel mesh cement board, straw board.

2, light steel building construction roofing systems 

2.1 Classification of lightweight steel roofing materials. 

Lightweight steel body construction materials roofing materials should be used with a lightweight, high strength, durability, fire resistance, thermal insulation, acoustic, seismic and other properties, while requiring a simple structure, easy construction, and to industrial production, such as pressure plate , space board, corrugated iron.In short, light steel structure building envelope systems in the design and construction must comply with the stress, stability, stiffness, waterproof, fireproof, heat insulation, sound insulation, shock, and the construction and maintenance requirements, in order to meet the design standards meet safety and normal use of the building.