Footing and Foundation Formwork: Typical Details

Footing forms are the simplest formwork on a job and the most repeated. A small mistake in one typical detail gets built eighteen times, and a footing set at the wrong level or in the wrong place is expensive to fix once the walls and columns sit on it.

This post covers what a footing form has to do, three typical cases from our projects (isolated footings, slab edges and deep boxes), and what a footing formwork drawing should show.

What a footing form has to do

• Hold the shape and the top level. The footing size and the top of footing elevation come from the structural drawings. The form has to deliver both, on often uneven ground.
• Resist the concrete. Footings are shallow, so the pressure is low. At the full liquid head of normal-weight concrete (about 150 lb/ft³), a 2 ft deep footing pushes about 300 lb/ft² at the bottom, a fifth of what a 10 ft wall sees. Stakes, cleats and kickers usually do the work that ties do in a wall.
• Stay put. The form must not float, shift or bulge while the concrete is placed and vibrated, especially at the bottom corners.
• Locate what goes in the concrete. Dowels, column starter bars, anchor bolts and waterstops are set against the form, so the form decides where they end up.

Isolated footings: one typical detail, counted

For a two-storey villa in Turks and Caicos, the first pour was 18 isolated footings. The drawing shows every footing on the grid, plus one typical footing form drawn once in plan, section and 3D:

• 1-inch wood panels stiffened with 2×2 and 2×4 lumber
• 2×4 lumber supports bracing the sides to the ground
• sections through each footing type, with all elevations measured from the ground floor level

The schedule turns the typical detail into an order: 26 sq ft of panel per footing, 474 sq ft for all 18; 36 ft of 2×2 and 81 ft of 2×4 per footing, so 648 ft and 1,464 ft in total. The pump vault area is listed separately. The supports of this pour are then reused in the next one.

Slab edges and slabs on grade

At a slab on grade, the edge form is the foundation form. For the chemical storage area of the Pineda Causeway BPS in Melbourne, Florida, the typical ground slab section shows:

• a wood panel edge form on 2×4 lumber
• a wood brace to a 2×4 stake driven deep into the ground
• a waterstop at the footing-to-wall joint, placed before the first pour
• plywood block-out boxes for the openings, reused in the next pour

On the UC Davis Equine Center, the slab edges around the treadmill area use 2 ft wood panels held by metal form stakes at 2 ft spacing, with lumber braces.

When the foundation becomes a box

Some foundations are really walls: pits, vaults and boxes cast on a base slab. On the F.M. Woods water treatment plant upgrade, the first pour was a box formed with 13 ft tall plywood panels, an inner wood box, 4×4 walers, ties and diagonal braces, with a waterstop at the joint to the base.

At that height the concrete pressure is wall pressure, so treat it as a wall: tie spacing, walers and pour rate as in Timber Wall Formwork: Ties, Walers and Bracing.

Where footing forms go wrong

• Level. The top of footing is set from the wrong datum. Give one reference level on the drawing and show the elevation on every footing type.
• Embeds. Dowels and anchor bolts are placed by eye. Show them on the form drawing and use templates for anchor bolts.
• Bottom corners. Corners open up under vibration. Detail the corner cleats and the bracing at the base.
• Soft ground. Stakes pull out. Give the stake length and spacing, and the support where the ground is poor.
• The first joint. The waterstop between footing and wall is forgotten until the wall is formed. Show it on the footing drawing.
• Counting. Material is ordered by the footing, by eye. A schedule per footing type and per pour orders it once.

What a footing formwork drawing should show

• A plan with every footing tagged on the grid, with its size and top elevation
• One typical form detail per footing type, in plan, section and 3D
• Stakes, cleats, kickers and braces, with their spacing
• Block-outs, embeds, dowels and waterstops
• Pour phases, and which forms are reused in the next pour
• Panel and lumber quantities per footing type and per pour

A note on engineering

Loads, bracing and the support of the forms must follow ACI 347R or your local code. If your contract or jurisdiction requires formwork drawings sealed by a licensed engineer, tell us when you ask for a quote.

For pour breaks and joints, see Formwork Shop Drawings and Construction Joint Layout. For suspended slabs, see Slab Shoring Layout: From Drawing to Site.