In building design for Nepal, there are several mandatory rule of thumb that architects and designers typically follow. While these rules may or may not be legally binding, they are based on experience and practical knowledge to ensure safe and functional buildings. The main objective of these Mandatory Rules of Thumb (MRT) is to provide ready-to-use dimensions and details for various structural and non-structural elements for ordinary residential buildings commonly built in Nepal. Their purpose is to replace the non-engineered construction presently adopted with pre-engineered construction so as to achieve the minimum seismic safety requirements. There are major three codes that explain the thumb rule for building design in Nepal. They are NBC 201, NBC 202 and NBC 205. NBC 201 is for RCC building with masonry infill. NBC 202 is for load bearing masonry building and NBC 205 talks about MRT for RCC building without masonry infill. Few important rule of thumbs for building design as per these codes are pointed below:
For Load Bearing Masonry Building
- Brick masonry with cement mortar can be used upto three storey building.
- Brick masonry with mud mortar can be used upto two storey.
- Stone masonry with cement mortar can be used upto two storey.
- The concrete to be used in footings, columns, beams and slabs, etc., shall have a minimum crushing strength of 15 kN/m² at 28 days for a 150 mm cube.
- Cement-sand mortar for masonry bond shall be of 1:6 and 1:4 for one-brick and half-brick thick walls, respectively.
- All plasters shall have a cement-sand mix not leaner than 1:6 on outside or inside faces.
- In order to achieve the full strength of masonry, the usual bonds specified for masonry shall be followed so that the vertical joints are broken properly from course to course.
- Openings should be as small and as centrally located as practicable.
- A building shall not be constructed if the proposed site is : water-logged, a rock-falling area, a landslide-prone area, a subsidence and/or fill area, and, a river bed or swamp area.
For RCC Building
- The span of beam shall not exceed 4.5m
- Each slab panels must be lesser than 13.5 square meter.
- The size of cantilever projection shall not exceed 1m.
- The length to width as well as height to width ratio of building must not exceed 3.
- The maximum height of structure is 11m or 3 storey whichever is less from the level of lateral restraint. However, an additional storey of smaller plan area(not exceeding 25% of typical floor area) shall be permitted.
- The length of wings on the structure shall restricted such that they are lesser than 25% of the length of rectangular part in either direction.
- No walls except a parapet wall shall be built on a cantilever slab. Such walls shall be constructed only if the cantilever slab is formed with beams.
- The foundation shall be at uniform level.
- Buildings shall not have soft storey.