This effectively states that all box gutters must allow for 30mm of freeboard which is from the overflow point eg.
Framing box gutter.
A box gutter is actually built into the bottom of the roof or into the roof overhang.
The foundation of most box gutters is wood that is then covered with thin sheet metal such as tin copper lead stainless steel or some other metal that will not readily corrode.
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Since they are not readily visible they typically don t alter the historic character of buildings and don t detract from or conceal decorative cornice details.
Copper gutter linings are most often built into wood framed supporting structures.
A box gutter does not hang onto the edge of a roof or on the edge or side of a house as many modern pre formed metal gutters do.
The kynar resin based coatings provide protection against weathering aging and pollution on commercial industrial and residential buildings.
Choose a trial width of box gutter minimum width is 300mm for commercial or 200mm for domestic.
Although the copper lining conforms closely to the gutter frame profile it should not fit tightly.
The most efficient hydraulic shape is width twice depth.
Rainhead overflow or specific box gutter overflow must be at least 30mm below the height of the back of the box gutter.
Unlike other gutters they are part of the roof structure.
If this gives a depth of box gutter that is too deep for the roof construction try a larger width etc etc.
Box gutters are composed of wood framing with a sheet metal lining normally copper stainless steel or galvanized steel.
The box is built by an experienced carpenter into the roof overhang or into the bottom of the roof then lined with the sheet metal.
Built in gutters also referred to as box gutters are considered a concealed roof drainage system.
The lining must be free to move.
They are most commonly found in older historical homes or buildings.
Box gutters are also known as parallel gutters trough gutters or built in gutter systems.
All domestic box gutters must be a minimum of 200mm wide and 75mm deep.