Gutters, downspouts and rainwater systems

Scope of supply

A pre-engineered building with a large roof sheds a lot of water in a short storm, so gutters and downspouts must be sized, not just added. World Steel supplies the complete rainwater system as part of the accessories package: see gutters and downspouts for the principles.

• Eave gutters in box or ogee shape, with end caps, outlets and expansion joints.
• Valley gutters for multi-gable roofs and internal gutters where specified.
• Downspouts (downpipes) with elbows, offsets, brackets and shoes.
• Gutter straps or brackets fixed to the eave strut, and overflow details.
• Sealant, rivets and fasteners.

Sizing and options

Gutters and downspouts are sized from the design rainfall intensity of the site, the roof catchment area and slope, and the outlet spacing. For each market the governing method differs, and overflow provisions are required so that a blocked outlet does not flood the building. Options include:

• Larger box gutters for long roof runs, with sumps and overflow weirs.
• Rainwater harvesting outlets connected to tanks by others.
• Leaf guards and gutter screens for sites near trees.
• Square or round downspouts, and concealed downspouts inside wall cladding where requested.

Materials and finishes

Gutters are usually formed from aluminium-zinc coated or pre-painted steel matching the trims; valley gutters that hold water for longer may be specified in heavier gauge, stainless steel or with a membrane lining. Downspouts can be in steel or in PVC supplied locally. Details at the eave are coordinated with trims and flashings and with the eave strut.

Compliance by market

Design references and accessories

See gutters and downspouts for sizing principles.

Documentation, packing and quotation

Deliverables include a roof drainage layout with outlet positions, sizing calculations to the stated code, details of joints, overflow and supports, and a component list. Gutters are nested in lengths with protective film and packed with the trims.

A quotation can be prepared quickly when the enquiry states the project location and the code to be used. Please send:

1. Site location or design rainfall intensity and return period.
2. Roof plan with slopes and any valleys.
3. Preferred gutter style, downspout material and colour.
4. Connection point to site drainage (by others).

World Steel returns a priced scope with a clear inclusions and exclusions list, the design basis assumed and a typical lead time. Enquiries go through the export supply team in Ho Chi Minh City.