Reference · 19 mixes

Mix ratios

What goes in the mixer, in what proportion, and what strength it reaches. Ratios are by volume unless noted. Every page is free - no sign-up. New to the notation? Concrete mix ratios explained covers what the numbers count, and mortar types M, S, N, O and K covers why the strongest mortar is usually the wrong one.

Concrete strength classes Mortar types (ASTM C270)Masonry grout Render & stucco Floor screed

7 mixes

Concrete strength classes

Nominal cement : sand : aggregate proportions and the strength each reaches.

M51 : 5 : 10725 psi · Blinding / levelling course under footings.M7.51 : 4 : 81,090 psi · Blinding, mass fill, non-structural pads.M101 : 3 : 61,450 psi · Levelling courses, path bedding, kerb backing.M151 : 2 : 42,175 psi · Paths, patios, shed and light slab bases.M201 : 1.5 : 32,900 psi · Driveways, footings, reinforced slabs (light).M251 : 1 : 23,625 psi · Reinforced footings, columns, structural slabs.M30Design mix4,350 psi · Structural columns, beams, suspended slabs.

5 mixes

Mortar types (ASTM C270)

The ASTM C270 types - cement : lime : sand - and where each belongs in a wall.

Type M1 : 0.25 : 32,500 psi · Below-grade, foundations, retaining walls, driveways.Type S1 : 0.5 : 4.51,800 psi · Exterior at/below grade, structural veneer, paving.Type N1 : 1 : 6750 psi · General above-grade brick & block, most common.Type O1 : 2 : 9350 psi · Interior non-load-bearing, tuck-pointing, repair.Type K1 : 3 : 1075 psi · Historic restoration of very soft masonry.

2 mixes

Masonry grout

High-slump grouts for filling block cores and bond beams around reinforcement.

Fine grout1 : 32,000 psi · Filling narrow block cores and reinforced cells.Coarse grout1 : 3 : 22,000 psi · Filling wider block cores and bond beams.

3 mixes

Render & stucco

Cement : lime : sand coats for exterior render and stucco, softest on top.

Scratch coat1 : 0.5 : 4.5First (keyed) coat of a two/three-coat render.Undercoat1 : 1 : 6Levelling undercoat on masonry walls.Finish coat1 : 2 : 9Final thin finish / stucco top coat.

2 mixes

Floor screed

Cement : sharp sand floor screeds, bonded and floating.

Bonded screed1 : 33,625 psi · Thin (25-40 mm) screed bonded to a slab.Floating screed1 : 42,900 psi · Screed over insulation or a membrane (50 mm+).

Reference, not a mix design. These are typical nominal proportions and strengths for planning and general work. Structural concrete is proportioned by weight from tested materials to a target strength - always follow your local building code and a qualified engineer's specification.