Indian Foundation Rules: Depth, Thickness & Concrete Grade (NBC 2016)

The requirement

Edition and scope. This page summarizes the stated older NBC 2016 reference. BIS now lists SP 7:2026. A model text is not a nationwide permit rule: confirm the local bye-law and adopted edition first. The newer standard’s clauses have not been checked here.

Every foundation in India must go down at least 500 mm below natural ground level. That is NBC 2016 §6.2.2. Footing thickness comes off Table 4: roughly 150 mm up to 300 mm, set by footing type. Width has no set number. Concrete for a reinforced footing starts at grade M20 under mild exposure.

These rules sit in NBC 2016 Part 6, “Structural Design”. Section 2 covers soils and foundations. Section 5A covers plain and reinforced concrete. Unlike some countries, NBC sets a flat minimum depth. It does not leave depth wholly to a site test.

Depth: 500 mm, and no frost figure. NBC 2016 §6.2.2 gives a baseline depth of at least 500 mm below natural ground level within that clause’s scope. The Code has no frost-line number anywhere. Frost is only named as one factor to weigh when a deeper footing is needed in fine sands or silts. That fits most of India, which has no frost-design rule at all. NBC also gives no set figure for hill or Himalayan regions. There the depth comes from a geotechnical study of your own site.

1. 1 footing
2. 2 ground

Width: a design job, not a table lookup. NBC does not fix a strip footing’s width. The width comes from structural design. That design checks your load against the soil’s allowable bearing capacity (§7.2). Get the ground assessed for your site and load. Then size the footing to carry that load. Don’t read a width off this page.

Thickness: read Table 4 for your footing type. Table 4 (§7.3.12) sets minimum thickness by footing type and support. It runs roughly from 150 mm to 300 mm. The low end is a reinforced concrete footing resting on soil. The top end is a masonry footing, or a reinforced concrete footing resting on piles. Read the figure for your own footing type off the table. One number does not cover every case.

Concrete grade. Do not assume a buried footing has mild exposure. The designer must assess the soil, groundwater and exposure class. NBC 2016 Part 6, Section 5A, Table 5 sets a minimum grade of M20 for reinforced concrete. Harsher exposure pushes the grade up.

What we won’t print — rebar cover

The research behind this page found two readings of the Code on rebar cover. So we are not printing a fixed number until that is settled. Check Table 16 (Part 6, Section 5A, §25.4.2). Use the cover figure that matches your project’s exposure class. Then confirm it with the engineer who designed the rebar before you pour.

Work out the concrete volume

Use the concrete sizes on the approved plan. Embedment is the depth from ground level to the base of the footing. It is not the thickness of concrete to pour. A strip, wall and trench fill each have their own shape. Work out each part on its own. Where parts meet, count that concrete once.

This example uses a straight concrete strip with the same size all along:

• Total concrete length: 20 m.
• Concrete width: 0.6 m.
• Concrete thickness, measured from its top to its underside: 0.5 m.

These are example sizes, not code limits or a footing design. Check the shape and size on the plans. Then check how deep the base must sit. It must meet the soil and frost rules for the site.

Volume = length × concrete width × concrete thickness.

20 × 0.6 × 0.5 = 6.0 m³.

That is the volume before any extra for waste or uneven ground. Measure the trench or forms. Agree the extra amount and final order with the supplier. The tool does the sum. It does not choose safe footing sizes.

Do it in 5 seconds

Related

• India’s building code hub. How the NBC model code gets adopted into state bye-laws.
• Setting out the stairs on the same build? See Indian stair rules.

Sources

• National Building Code of India 2016 (NBC 2016 / SP 7:2016), Bureau of Indian Standards — Part 6, Section 2 §6.2.2 and §7.2/§7.3.12 (foundation depth, width and thickness table) and Section 5A Table 5 / Table 16 (concrete grade, rebar cover). For full text and access options, check the current status at bis.gov.in.

Read this first. These figures are from NBC 2016, which BIS has withdrawn and replaced with SP 7:2026 (“National Building Construction Standards 2026”), gazette-notified in 2026 (reported 30 April 2026) and now BIS’s current national standard. NBC is also a model code: it has no legal force until your state or municipality adopts it into its own bye-laws — and local instruments may use a fixed edition or an updated reference. Confirm which edition your local bye-law currently adopts, and get your ground checked with a proper site investigation, before you dig.