How the two differ in kind
A brick veneer has two entirely separate structural needs, and the components that meet them are frequently discussed as though they were interchangeable.
WALL TIES restrain it LATERALLY. Wind pressing on the veneer and, more severely, sucking on it has to be transferred back to the structure behind, and the ties do that — in tension and in compression, at a density set by the wind load, the cavity width and the tie's own capacity. They also hold the veneer plumb during construction and through its life. What they do not do is carry its weight, beyond an incidental amount.
SHELF ANGLES carry the WEIGHT. Brick is heavy, and a tall veneer cannot simply stack from the ground: differential movement between the veneer and the frame behind it, and the sheer accumulated load, mean the weight has to be handed to the structure at intervals — typically at floor lines above a certain height, with the requirement and the spacing set by the code and the backing type. A steel angle is bolted to the structure, the veneer above sits on it, and the load goes into the frame.
The detail that makes that work is the SOFT JOINT immediately beneath the angle: a compressible joint, sealed rather than mortared, that leaves the veneer above free to be supported by the angle without bearing on the veneer below. Without it the angle supports nothing, because the brickwork is continuous through it.
That joint is also the detail most often destroyed, by a bricklayer filling it with mortar because an open joint looks unfinished. The consequence is not cosmetic. Brick GROWS — fired clay takes up moisture and expands irreversibly for years after manufacture — and a veneer with nowhere to expand goes into compression, which appears as spalling at the angle, bowing of the wall, and cracking at the corners.
The factors that actually differ
Show
| Shelf angles | Wall ties | |
|---|---|---|
| What it carries | The veneer's weight, into the structure at intervals. | Lateral load — wind pressure and suction — and essentially none of the weight. |
| What sets the quantity | The weight of veneer above it, the span between its fixings, and the eccentricity of the load on the angle. | Wind load, cavity width, tie capacity, and a maximum spacing — with tighter spacing at openings and edges. |
| Where it goes | At floor lines above the height at which the code requires intermediate support. | Distributed over the whole wall, at a density, with additional ties around every opening. |
| The critical accompanying detail | A soft joint immediately beneath, which is what lets the angle relieve the veneer above. | Correct embedment in the bed joint and a drip or a slope so water cannot track inward along the tie. |
| How it is defeated | Mortaring the soft joint solid, which makes the veneer continuous and the angle useless. | Ties omitted, spaced too far, installed sloping the wrong way, or not embedded far enough into the bed joint. |
| What failure looks like | Spalling at the angle, bowing of the wall, cracking at corners — the signature of a veneer in compression. | The veneer bowing or, in an extreme wind event, detaching. |
| Corrosion | A steel angle in a cavity needs corrosion protection and a route for water off it, or it rusts and jacks the brickwork apart. | Same concern — tie material and coating are specified for the exposure. |
| Drainage interaction | The angle interrupts the cavity, so flashing over it and weeps above it are required, or water collects on the angle. | Ties should not bridge water across the cavity; a drip or slope is part of the design. |
| Movement | The reason it exists at height — brick expands irreversibly for years and cannot be allowed to accumulate. | Ties permit small differential movement between veneer and backing. |
| Both required | Yes, above the height at which intermediate support is needed. | Yes, always, on every veneer regardless of height. |
Which one, and when
Choose shelf angles when…
- A veneer tall enough that the code requires intermediate support — which above a modest height it does.
- A framed backing, where differential movement between veneer and frame makes relief essential.
- Over an opening or a soffit, where the veneer above has nothing beneath it.
- Wherever the veneer's accumulated weight would otherwise be carried on brickwork below that was never designed for it.
Choose wall ties when…
- Every veneer, at every height — ties are not optional and not a function of height.
- Around every opening and at every free edge, where the density is increased.
- Wherever the cavity width or the wind exposure changes, since both affect the required density.
- As the check on an existing wall that is bowing, since inadequate or corroded ties are the usual cause.
Now run your own numbers
This page holds no prices on purpose — a national average is wrong for almost every real project. Quantify both options with your dimensions and your local quotes.
Frequently asked questions
- What does the soft joint actually do?
- It separates the veneer above the shelf angle from the veneer below it, so the angle can support the upper brickwork without that brickwork bearing on the lower. Without the joint the veneer is a continuous column of masonry from the ground upward, the angle carries nothing, and the load it was installed to relieve continues down as though it were not there. The joint also accommodates movement: the veneer expands upward and the structure behind it may shorten or deflect, and a compressible joint at every angle gives that movement somewhere to go. It is formed with a compressible filler and closed with a sealant rather than mortar — visually a sealed joint rather than an open gap, which is what makes it acceptable to look at and is why the correct detail exists.
- Why does brickwork expand permanently?
- Because fired clay takes up moisture from the air after it leaves the kiln and expands as it does, and that expansion is largely IRREVERSIBLE — it is not the seasonal wetting and drying of a material that returns to its original size. The rate is highest immediately after firing and continues at a decreasing rate for years, so a wall built with young brick expands measurably over its early life and keeps creeping afterwards. This is why brick veneer needs movement provision in both directions: vertical, through the soft joints at shelf angles, and horizontal, through vertical movement joints at spacings and at corners. It also runs opposite to concrete and to the timber or steel frame behind, which shrink — so the differential movement across the cavity is larger than either material's own movement.
- What happens when the soft joint is mortared solid?
- The veneer becomes continuous through the angle, and the expansion that had nowhere else to go puts the brickwork into compression. The visible consequences are consistent: spalling of the brick faces immediately below the angle, where the stress concentrates; bowing of the veneer, because a compressed panel restrained at its edges buckles outward; and cracking at corners and at the ends of walls where the expansion is trying to relieve itself. The angle itself is then loaded by brickwork bearing on it from below as well as above, which is not what it was designed for. It is one of the most common defects in brick veneer construction, it is a workmanship error rather than a design one, and it is worth inspecting for specifically, since a mortared joint is easy to see from the ground.
- How many ties does a veneer need?
- A density set by the wind load, the cavity width and the tie's own rated capacity, subject to maximum spacings in both directions — and with additional ties in specific places. The wind load determines the force each tie must transfer in tension and compression; the cavity width matters because a tie spanning a wide cavity buckles more readily in compression; and the tie's capacity comes from its type and its embedment. Beyond the general density, codes require closer spacing around openings, at unsupported edges, and at the top of the wall — because the veneer is least restrained there and the local wind pressures are highest at corners and edges, exactly as they are on a roof. Increasing the general spacing while ignoring those local requirements is a common shortfall.
- Do ties carry any of the weight?
- Essentially none, and expecting them to is a misunderstanding worth correcting. A conventional veneer tie is designed to transfer load perpendicular to the wall — tension when the wind sucks and compression when it presses — and is not rated to carry the veneer's weight in shear along the wall plane. The weight travels down through the masonry itself to whatever supports it: the foundation at the base, and a shelf angle at each level where intermediate support is required. The distinction matters because it identifies what is actually failing when a veneer moves: a bowing wall is a tie problem, while a veneer that has settled, spalled at a horizontal line, or cracked above an opening is a support problem. Different symptoms, different components, different remedies.
- Why does a shelf angle need flashing and weeps?
- Because it interrupts the cavity, and a cavity's job is to drain. Water that has penetrated the veneer runs down the back of the brickwork and down the cavity, and a steel angle projecting into that path is a shelf for it to collect on. Flashing over the angle collects that water and directs it back out through weep holes in the course immediately above, which is why weeps appear in a line above every shelf angle as well as at the base of the wall. Omit either and water sits on the angle — corroding it, saturating the brickwork above and below, and eventually appearing inside. Corrosion on a shelf angle is particularly damaging because rust occupies more volume than the steel it came from, so a rusting angle jacks the brickwork above it apart.
- At what height is intermediate support required?
- Above a height the code sets, and the threshold depends on the backing and on the jurisdiction, so the local code governs rather than any figure quoted generally. The reasoning behind the requirement is consistent everywhere: the accumulated weight of a tall veneer is substantial; a framed backing shrinks and deflects while the veneer expands, so their relative movement grows with height; and a veneer supported only at its base has no way to relieve either. Where the backing is masonry or concrete rather than a frame, the differential movement is smaller and the permitted height is generally greater. The practical consequence for a two-storey house is that shelf angles are often not required at all, while a multi-storey building has one at essentially every floor.
- How do I tell which problem an existing wall has?
- By where and how it has moved, and the patterns are distinct enough to diagnose from the ground. A veneer bowing outward between floor lines, with the bow greatest at mid-height, points at ties — too few, corroded, or never installed, which is a well-documented defect in some periods of construction. Spalled brick faces in a horizontal band, cracking that steps through the bed joints at a consistent level, and a visible line of crushed or mortar-filled joints point at a shelf angle whose soft joint has been lost or that is corroding. Vertical cracking at corners and at the ends of long walls points at missing or inadequate movement joints. Rust staining at a horizontal line is a shelf angle corroding. All of these warrant a structural inspection rather than a repair to the visible symptom.