Masonry design
Masonry carries load in compression through walls and piers built from bricks or blocks bedded in mortar, and it remains the everyday structure of most UK homes. We assess and design masonry to the Eurocodes for clients across the UK.
What decides how much load a masonry wall can carry?
Rarely just the strength of the bricks. Slenderness, the wall's height against its thickness, and the eccentricity of the load usually govern, because a slender or off-centre loaded wall buckles before it crushes. We check both, along with the restraint the floors and return walls provide.
How masonry carries load
Masonry is strong in compression and weak in tension, so it works best as walls and piers that carry vertical load down to the foundations and resist crushing. Its strength comes from the units, the bricks or blocks, working together with the mortar joints, and the design value depends on the unit strength, the mortar class and how the two combine, expressed as a characteristic compressive strength for the masonry as a whole. Because it cannot be relied on in tension, masonry needs help wherever bending occurs, from lintels over openings to ties and returns that stop tall walls bending under wind.
The behaviour that most often governs masonry is not crushing but stability. A wall is a slender element, so its slenderness ratio, the effective height against the thickness, together with the eccentricity of the load, sets how much of its compressive strength it can actually use. A slender or eccentrically loaded wall buckles long before it crushes. This is why panel restraint, floors and roofs propping the top of a wall, and return walls giving lateral support all feature so heavily in masonry design, and why removing a length of wall can matter more than it first appears.
Designing to BS EN 1996
Masonry is designed to BS EN 1996, Eurocode 6, with the UK National Annex. For vertical load we check the compressive capacity of the wall or pier, allowing for slenderness and the eccentricity of the load from floors and beams bearing on it. For lateral load, mainly wind on external walls and the effect of any propping, we check the panel spanning between its supports, treating it as bending in one or two directions depending on how it is held on its edges. Where a concentrated load lands, from a beam end or padstone, we check the bearing stress under it.
Movement and detailing carry as much weight as the numbers. Clay bricks expand over time and concrete blocks shrink, so movement joints are placed to stop these built-in movements cracking the wall, and wall ties, bed-joint reinforcement and cavity details all feed into the design. Where masonry has to resist more than plain walling can, we introduce reinforced or post-tensioned masonry, bars set into pockets or bed joints, though for most projects the answer is a sensible layout of solid wall, returns and openings that keeps the masonry in the compression it is good at.
Durability, exposure and where masonry suits
Masonry durability is mostly about water and frost. Units and mortar are graded for exposure, and in wet or freezing conditions we specify frost-resistant units and the right mortar and sulfate class so the wall does not spall or the joints erode. Below ground and near the ground, where masonry meets damp, we specify engineering bricks or dense units and coordinate the damp-proof course, because sustained saturation and freeze-thaw are what break masonry down over decades rather than any structural overload.
Masonry suits load-bearing walls in houses and low-rise buildings, cavity external walls, party walls, retaining and boundary walls and piers, where its compressive strength, fire resistance, sound insulation and low maintenance all count in its favour. Its limits are tension and span, so it needs lintels and beams over openings and cannot form long horizontal spans itself, and it is heavy, which the foundations have to carry. We work with the material's strengths, designing the walls, piers and lintels and checking what an opening or alteration does to the load paths around it.
What we check.
The points our calculations resolve for a project like this.
- Characteristic compressive strength from unit strength and mortar class
- Slenderness and load eccentricity governing wall capacity
- Lateral and wind design of panels spanning between supports
- Bearing stress under beam ends and concentrated loads
- Movement joints for brick expansion and block shrinkage
- Frost and sulfate exposure grading for durability
From enquiry to sign-off.
Enquiry
Send drawings or describe the problem. We confirm the scope, the deliverables and a target timescale.
Information
We agree the survey, drawings or data we need and any site access required.
Engineering
Design, calculation or assessment to the relevant Eurocodes and UK National Annex.
Issue
A clear, defensible report or set of calculations, with assumptions and limitations stated.
Common questions
What decides how much load a masonry wall can carry?
Rarely just the strength of the bricks. Slenderness, the wall's height against its thickness, and the eccentricity of the load usually govern, because a slender or off-centre loaded wall buckles before it crushes. We check both, along with the restraint the floors and return walls provide.
Why do walls need movement joints?
Because the materials move. Clay bricks expand over years and concrete blocks shrink as they dry, and without joints to relieve this the wall cracks. We place movement joints at the spacings Eurocode 6 and good practice set, so built-in movement does not show as cracking later.
Can masonry be reinforced?
Yes. Bed-joint reinforcement, and bars set into pockets or hollow blocks, let masonry carry bending and lateral load it could not manage plain, and post-tensioning can be used for taller or more heavily loaded walls. For most projects a sensible layout of solid walls, returns and lintels does the job without it.
Is masonry good in fire?
Generally yes. Masonry has good inherent fire resistance and provides useful sound insulation, which is why party and separating walls are so often built from it. The period of resistance depends on the wall thickness and materials, and we confirm it against the relevant guidance for the building.
Tell us what you are building.
Send the drawings or describe the project. We confirm scope, deliverables and a realistic timescale.
Start a project