Understanding brick mortars | Features

TABLE 1: MORTAR MIXES
This table lists four types of mortar based on Portland cement as a binder and the proportions, by volume, of the constituents in various mixes. Mixes are grouped in four designations of approximately equal strength and durability.
Type of mortar		Cement:lime:sand	Masonry cement:sand		Cement:sand (plasticised)
Binder content		Portland cement and lime, with or without air entraining additive	Masonry cement containing Portland cement and lime in approx. 1:1 ratio, and air entraining additive	Masonry cement containing Portland cement (min 75%) and inorganic materials other than lime and air entraining additive	Portland cement and an air entraining additive
Designation	(i)	1:0 to 0.25:3	-	-	-
	(ii)	1:0.5:4 to 4.5	1:3	1:2.5 to 3.5	1:3 to 4
	(iii)	1:1:5 to 6	1:3.5 to 4	1:4 to 5	1:5 to 6
	(iv)	1:2:8 to 9	1:4.5	1:5.5 to 6.5	1:7 to 8
Note: The range of sand volumes noted in this table allow for the differences in grading on the void volume. The lower volumes apply to Type G graded sands of BS 1199 and 1200 and the higher volumes to Type S. Mortar with both lime and air entrainment can be used with any sands within grading defined in BS 1199 and 1200.

TABLE 2: BRICK AND MORTAR SPECIFICATIONS
This table offers the appropriate specification of clay bricks and mortar for various building types
Situation	Brick durability		Mortar designation	Remarks
	BS 3921	EN 771-1
Work below or near external ground level
Low risk of saturation, with or without freezing	FL, FN, ML or MN	F1 or F2: S1 or S2	(i), (ii) or (iii)
High risk of saturation, with freezing	FL FN F2:	F2: S2 S1	(i) or (ii) (i) or (ii*)	* with SRPC
Drainage manholes	FL, FN, ML or MN	F1 or F2:S1 or S2	(i)
External walls of buildings (unrendered) excluding chimneys, parapets, cappings, copings and sills
Low risk of saturation	FL, FN, ML or MN	F1 or F2:S1 or S2	(i), (ii) or (iii)
High risk of saturation	FL FN	F2: S2 F2: S1	(i) or (ii) (i) or (ii*)	* with SRPC
Parapet walls (unrendered)
Low risk of saturation, e.g. low parapets with copings on some single storey buildings	FL or ML FN or MN	F1, F2: S2 F1, F2: S1	(i), (ii) or (iii) (i), (ii) or (iii)	* with SRPC
High risk of saturation, e.g. where only a capping is provided	FL FN	F2: S2 F2: S1	(i) or (ii) (i) or (ii*)	* with SRPC
Cappings, copings and sills
Cappings, copings and sills	FL or FN	F2: S1 or S2	(i)	Bed DPCs under cappings, copings and sills in the same mortar
Freestanding garden walls
With coping	FL or ML FN or MN	F1, F2: S2 F1, F2: S1	(i), (ii) or (iii) (i) or (ii)	(ii) mortar with SRPC in exposed locations
With capping	FL FN	F2: S2 F2: S1	(i) or (ii) (i) or (ii) with SRPC
*Earth retaining walls Backfilling with free-draining material is strongly recommended**
With coping and waterproof membrane on retaining face	FL or ML FN or MN	F1, F2: S2 F1, F2: S1	(i) or (ii) (i) or (ii*)	* with SRPC
With capping, or with coping but no waterproof membrane on retaining face	FL or FN	F2: S1 or S2	(i)	A waterproof membrane on the retaining face is strongly recommended
Note: BS 3921: 1985, the British Standard Specification for Clay Bricks, is in the process of being replaced by BS EN 771-1: 2003, the European Standard for Clay Masonry Units. They will run concurrently until early 2005.
Key
Designation letters for brick durability and soluble salts content differ between BS 3921 and EN 771-1.
In BS 3921:1985
Brick durability: F=frost resistant M=moderately frost resistant O=not frost resistant
Soluble salts content: L=low soluble salts content N=normal soluble salts content
In BS EN 771-1:2003
Brick durability: F2=severe exposure F1=moderate exposure F0=passive exposure
Soluble salts content: S2=lower content category S1=higher content category S0=No requirement category
SRPC=Sulphate resisting Portland cement