Lime VS Portland Cement? Which Is Better?
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There are only two kinds of cement used in masonry, Lime and Portland.
Cement is like flour, the essential ingredient in baking that can be used to make bread, muffins, etc. Similarly, cement is the essential ingredient for brick mortar, concrete and paving stones. Many people confuse cement and concrete, but they are not the same: Cement is like the flour and concrete is like the bread. Cement is basically the glue of masonry.
So this brings us back to our original question: Which is better, lime cement or Portland? Each has its pros and cons.
Portland Pros | Portland Cons | Lime Pros | Lime Cons |
| High Strength | No Flexibility | Flexibility | Slow set time |
| Quick Set Time | Impermeable to water | Autogenous healing | Low strength |
| Sets Underwater | Bad for Environment | Permeability | |
| Less Expensive | High Strength | Workability | |
| Better for Environment |
Mortar Types
Since each cement has different good and bad qualities, most common mortars combine both types of cement. There are 5 main types of mortar, suitable in different applications, each with different strengths, properties and applications.
Type M – 3200 PSI – 100% Portland
Type S – 2200 PSI – 67% Portland – 33% lime
Type N – 1400 PSI – 50% Portland – 50% lime
Type O – 1000 PSI – 33% Portland – 67% lime
Type K – 750 PSI – 100% lime
Bricks and wall stones are usually laid in Type N. This 50-50 mix combines the good qualities of the Portland (strength and fast set time) with the flexibility, permeability and workability of lime.
Type M (pure Portland) or Type S must be used for anything exposed horizontally to the elements, such as a stone patio, door threshold or wall coping. This is because water pooling and salt will quickly erode the surface (usually within one year) if the mortar is Type N or lower.
Types O and K are rarely used (Type O is usually for glass block and Type K is practice mortar).
Types of Lime
The element that gives the cement strength is the clay content. Portland cement is about 30% clay-based, while lime is usually about 5% clay. However, there are three basic strengths of lime mortar, depending on the amount of clay present. The closer the clay percentage gets to 30%, the closer it is to a Portland cement, since the strength will be the same.
So Which Type of Cement Is Better?
There is no right or wrong type of cement, but there are many right and wrong applications of each. This leads to confusion as to what ratio is right for each circumstance. Many people know that using pure Portland on natural stone is bad (and it is), but in our Canadian climate you have to lay a flagstone patio in pure Portland if you want it to last more than a couple of years. Lime and Portland cements are equally useful to the trade, and only knowledge and experience will tell you what the right cement or ratio is.
Is the lime that is mixed with Portland cement in types S, N and O mortar. hydraulic or non-hydraulic?
Hello there. I suppose one feature has been left out in comparing the pros and cons of the two cements – the life of the mortar in which lime fares far better than portland. Again the strength of the mortar is perhaps evaluated only for short term, if compared for a period of say, a 100 years, perhaps lime again would fare better.
Very well written article.
Prem Pratick Kumar
So what do you use on stone foundation walls, on the exterior, for repointing above-grade, rubble stone foundation walls? My understanding is that the Portland is bad, so which of those grades do you use instead?
Well written article, perhaps if more Mason were familiar with these principles we would have less project failures. Air floated clay can also be used to make mortar mixes instead of lime. Also like to point out that mixes should be tailored to the strength of the material you are laying(ie laying reclaims with high lime content). That way if there is movement in a structure it will crack the mortar joints and not the material itself making repair a lot easier.
Please in your next post discuss the significance of the lime mortars, historically, and please define their ability to breathe.
I have damp issues on internal walls ,ive re-rendered with sand ,cement and waterproof add mix 5 yrs ago ,we also had the cavity filled with insulation ..
i think the walls are sweating ,if i had rendered with lime would this have happened I’m going to extract the cavity.
the walls were originally lime mix and cavity free…
Hi, I would like to know what ratio to mix lime with what. I don’t want to use portland cement. Do I have to add clay to the mix?
Typically Portland cement is mixed with hydrated lime, sand, and water to make mortar. Lime putty mortars are not very common for new construction but are more often used on historic building constructed with lime putty mortars. Additionally there are two other types of cement that are often used for preparing mortar. They are masonry cement and mortar cement. Refer to ASTM C270 for more information. Masonry cement and mortar cement are proprietary products that contain either Portland cement or blended cements that are mixed with a plasticiser such as hydrated lime of ground limestone along with other materials to enhance he mortar properties such as workability or air entrainment. Masonry cement mortars are the predominant mortar type for the southeast United States.
Thanks for the info.
Toduochwn! That’s a really cool way of putting it!
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My take is this:
Lime is beautiful, had been used for facades, blocks, in building in the past. Mold free (but not water tight!)
Today lime is in portland cement, brick mortar, maybe drywall and compounds, plasters, pool liners, more: but carefully and mixed with other things.
However it’s not suggested for (outdoor/wet) floors or in bathroom / steam rooms or with (ceramic) tile for many technical reasons (issues that arise a customer would complain about, or long-term commercial liability if it fails long-term).
For DiY for niche use (anywhere not critical) lime is a great project. For professional use, let the manufacturers do the mixing and use only the approved mixes for applications 🙂