How it differs from concrete
The difference is the coarse aggregate.
**Mortar** is cement, fine sand and water. It beds, fills and renders, but it is not meant to carry load.
**Concrete** also contains gravel. That gravel is what gives it structural strength, which is why a slab, a footing or a column is made of concrete and never of mortar.
A third word that gets mixed up with both: **cement** is only the powder in the bag, the binder that makes everything else stick.
The mortars people actually use
**Bedding or bricklaying mortar.** The traditional one, cement and sand. For laying block and brick, and for bedding units.
**Bastard or cement-lime mortar.** It also contains lime. It is more plastic, far nicer to work with and lets the wall breathe, which makes it the right choice in restoration and traditional construction, where a cement-only mortar damages the stone.
**Tile adhesive (cementitious adhesive).** For fixing ceramics. It is not a bedding mortar: it is formulated to bond to a smooth surface and goes on in a thin bed.
**One-coat render.** A facade render that acts as both undercoat and finish, and comes ready coloured.
**Self-levelling compound.** Very fluid, spreads out on its own and finds its own level. For preparing floors before a covering.
**Repair mortar.** Thixotropic, stays put on vertical and overhead surfaces without slumping. For making good damaged concrete.
**Renovating render.** Porous, lets moisture evaporate out of the wall and holds the salts. For rising damp.
**Refractory mortar.** Withstands high temperatures. For chimneys, ovens and barbecues.
The traditional mixes
They are expressed as parts of cement to parts of sand.
- **1:3** — a rich, strong mortar. For external render and work that has to last.
- **1:4** — the general-purpose one, the most commonly mixed.
- **1:5 or 1:6** — a lean mortar, for filling and undemanding work.
- **1:1:6** (cement, lime, sand) — the bastard mix, the pleasantest to work with.
That said: most jobs today are done with bagged ready-mixed mortar, batched at the factory. It costs a little more per square metre and is almost always worth it, because the result is the same on Monday as on Friday.
How to mix it
- Put in **most of the water** first, not all of it, then the powder. The other way round leaves lumps at the bottom of the bucket.
- Mix with a paddle on a drill at low speed, until there are no lumps.
- **Let it stand for five minutes** and mix again briefly. This step is nearly always skipped and it is the one that lets the admixtures do their work.
- Adjust the water **before** it stands, never after.
Water: the mistake that ruins everything
Adding extra water is the easiest thing to do and the most expensive. Mortar with too much water flows better and feels easier, but:
- It loses a noticeable amount of strength.
- It shrinks more as it dries, and therefore cracks.
- It separates: the water rises and the cement sinks.
The quantity on the bag is not a suggestion. If the mortar will not flow, something else is wrong: usually the substrate is dry and is drawing the water out, and that is fixed by dampening or priming it first.
Two more things
**Pot life.** Once mixed you have a while to use it, usually one or two hours. After that it cannot be “revived” by adding water: what comes out of that will not bond.
**Cold and heat.** Below 5 °C setting stops; above 30 °C, or in wind, mortar dries before it sets and ends up dusty. In summer in Menorca it pays to work first thing and to dampen the substrate.
Tell us what you are doing
We stock ready-mixed mortars for every one of these jobs, and sand and cement if you would rather mix your own. Give us the area and the type of work and we will tell you which one suits and how much you need.