Interior assemblies · Partitions & Linings
Internal Masonry Partition System
This entry explains the internal masonry partition as a heavy element that carries no load: why its own weight decides what has to be under it, why the head detail has to tie it without bearing on it, and why cutting a chase into it is a different act from running a cable through a framed wall.
Educational reference entry. How this system behaves depends on climate, jurisdiction, loading, substrate, the adjacent systems it meets, how the building is used, the manufacturer's instructions and qualified professional design.
Overview
What masonry partition is
An internal masonry partition is a wall of bonded units built between rooms, taking no floor or roof load. It is a solid element rather than a faced cavity: the units are laid in bond so the wall acts as one thing, a finish is applied directly to the background, and there is nothing inside it. Everything it can be asked to do, and everything that can be done to it afterwards, follows from that solidity.
The wall carries nothing and still weighs something, and that combination is the whole of its identity. A framed partition is light enough that where it stands is usually a matter of layout; a masonry partition arriving on a floor is a line load on that floor, so moving it in plan is a question for whoever designed the structure beneath rather than for whoever is drawing the rooms.
The boundary against the framed partition is not the appearance of the finished wall, which can be identical, but the absence of a cavity. A framed partition's whole logic is the space between its faces, which carries infill, services and concealed backing; a masonry partition has no such space, so every one of those duties has to be answered differently. Services are buried in the thickness rather than threaded through a void, and anything to be fixed later is fixed into the wall rather than into something built in behind the face.
It is equally not a loadbearing masonry wall, which is the same construction doing a different job: there the floors and roof bear on the wall and the wall holds them up, and the building's stability depends on it. Here the wall is a division that happens to be heavy, and the head detail exists specifically to make sure it never starts carrying anything. It is also not a separating wall, which exists to divide separately occupied spaces and is designed against a transmission path rather than against a plan.
Terminology
Common names and aliases
These names describe the same assembly. The encyclopedia keeps one entry per system so that a trade term or a regional name never becomes a second, thinner page.
- block partition
- blockwork partition
- non-loadbearing masonry wall
- internal block wall
- solid internal partition
- brick or block internal wall
Purpose
What this system is intended to do
The job the assembly exists to perform, conceptually. An intention is not a guarantee that any particular build achieves it.
- Divide interior space with a solid element that takes no floor or roof load from the structure above it.
- Deliver its own weight down a line that the construction beneath it was arranged to receive.
- Be held against lateral action at its head and its vertical edges without those restraints transferring vertical load into it.
- Receive buried services within its own thickness, at positions agreed before the wall is built rather than found afterwards.
- Present a background to which a finish is bonded directly, with no frame and no void between the two.
- Accommodate movement in the structure above and along the run without passing it into the finished face.
Composition
The roles this system is made of
What each part does in the assembly and what it depends on — never a product, a thickness, a fixing or a determination that anything is adequate for the role.
Order is not meaningful in this system. These roles interact as parts of one whole rather than stacking up in a sequence, so the list below is not a build-up and nothing should be read into the order it appears in.
- Primary supportThe wall body, laid in bond
The bonded units that make the wall a single element rather than stacked pieces. It carries nothing from above and carries itself, which is enough to make its own stability, its restraint and its support a structural conversation rather than a layout one.
- SubstrateThe supporting line beneath the wall
The slab, the suspended deck, the beam introduced for the purpose, or the ground-bearing construction the wall is built off. It is a component of this system because the wall's weight has to arrive somewhere, and whether the thing beneath was arranged to receive it is settled before the wall is set out, not after it is up.
- AttachmentHead restraint against the soffit
The connection at the top of the wall that holds it in position laterally while leaving it free of vertical load. It is the hardest detail in the system because it is asked to do one thing and refuse another at the same point, and it is the detail most often replaced on site by simply building the wall tight.
- AttachmentTies and restraint at the vertical edges
The connections where the partition meets flanking walls, returns and columns. They hold the wall's vertical edges in line and are the reason a long run stands as a wall rather than as a slender panel, which is why an opening cut near an edge is not the same as one cut in the middle of a run.
- Edge and terminationSupport over openings
The member spanning a door or hatch, carrying the masonry above the opening back to the wall on either side. A partition carries no building load and still has to carry itself over a hole, so an opening in this wall is a small structural arrangement rather than a gap left in a frame.
- Service zoneChases, recesses and boxes cut into the thickness
The channels and pockets cut or formed so cables, pipes and accessories can be buried and covered by the finish. What distinguishes them from a service run in a framed partition is that they remove part of the element itself, so where they are, how they run and how they are made good are questions about the wall rather than about the services.
- Finish surfacePlaster or bonded board applied to the background
The finish applied directly to the masonry, whether wet or as board fixed on adhesive. It is bonded to the wall rather than carried on a frame, so it follows the wall's movement instead of spanning across it and reports anything the wall does straight through to the room.
- Jointing and sealingMortar joints, movement provision and the closure at the head
The bedding between units, any joints deliberately left within a long run, and whatever closes the gap at the head. The closure at the head is the one that goes wrong most often, because anything rigid placed across a gap that exists to permit movement has quietly cancelled the detail it was meant to complete.
Interaction
How the parts work together
The reason this is a system rather than a list of parts: what depends on what, and what stops working when one part is changed.
Weight is the origin of everything else in this system. The wall's own mass has to arrive on a line beneath it, so moving the partition in plan moves a load, and the floor or beam below becomes the thing to be examined rather than the wall being moved. A framed partition relocated on a drawing is a layout change; this one is a structural question, and it is the reason a plan marked up late in a project can stall on a wall nobody thought was structural.
The head detail is a contradiction held in one place: it must tie the wall against lateral action and must not let it pick up vertical load. Build the masonry hard up to a soffit that will deflect and only two things can follow, both bad — either the wall begins carrying the floor above it, which nothing designed it to do, or the finish and the junction crack as the soffit comes down onto it. The detail that avoids both is a restraint with a gap, and the gap has to survive everybody who works there afterwards.
A chase removes material from the element that is holding the wall up, which is not true anywhere else in interior construction. In a framed partition the same cable occupies a void that was already there and takes nothing away. Here, the depth of a chase, the direction it runs and how close two of them come to each other are all reductions in a solid element's own section, which is why chasing is coordinated in advance rather than resolved by whoever arrives with the conduit.
The finish behaves as part of the wall rather than as a layer over it. Bonded plaster or board on adhesive follows the background, so a movement joint in the masonry that is plastered straight across is no longer a movement joint, and the gap left at the head that is filled solid with the same finish has become the load path it existed to avoid. The finishing trade can therefore undo the two details that define this system without any instruction to do so and without anything visible changing.
Materials
Material families commonly met in each role
Commonly encountered, not recommended. Whether a material suits a given project depends on the whole assembly, the exposure, the manufacturer's documentation and qualified professional review.
Primary support
Unit families of these kinds are commonly encountered in internal partitions. They differ in weight, in how they take a fixing and in how readily they are cut, and which of those properties matters is decided by what the wall is being asked to carry, hold and receive rather than by the family alone.
Jointing and sealing
Bedding mortars, compressible packing at a head gap and sealant families are commonly encountered in closing this construction. Where fire provisions have been determined by others, sealant families intended for those junctions appear here; the determination itself sits outside this entry.
Attachment
Tie and restraint components at the head and at the vertical edges are commonly formed in these families. Which component belongs in a particular restraint, and what it is capable of, comes from the manufacturer's documentation and the designer.
Edge and termination
Members spanning openings in internal masonry are commonly drawn from these families. What any of them can span, and what has to bear where, is a structural determination for the particular wall.
Finish surface
Wet plaster families, board fixed on adhesive and the beads that terminate them are commonly encountered as the finish to a masonry background. How a finish behaves at a head gap and at a movement joint matters more to this system than how it behaves across the face of the wall.
Service zone
Materials from these groups are commonly encountered where a chase is made good and the finish carried over it. Making good a chase restores the surface rather than the section of the wall, which is a distinction worth keeping in view.
Boundary
Where this system ends and meets another
The edge of this system. Everything above is inside it; each junction below is a condition at its boundary, where an adjacent system or an adjacent building condition takes over. Junctions are where most assemblies actually fail, so they are set out explicitly rather than left inside the prose. What resolves one is a detail designed for the specific building — not a rule of thumb.
A heavy partition standing on a joisted floor
A masonry wall built on a timber floor applies a line load to members chosen for a distributed one. Whether the floor can take it, and whether the wall sits over a joist, between joists or on something introduced beneath it, is a structural question answered before the wall is set out.
Read about Timber Joisted Upper Floor →The head against a soffit that will deflect
A cast plate goes on moving after it is built, so the gap left above a partition beneath it is an allowance for something that has not finished happening. What the head restraint has to accommodate is taken from the frame designer rather than assumed, and it is the number the finishing detail at the head has to respect.
Read about Concrete Frame →A masonry wall meeting an isolated floor build-up
Whether the partition stands on the structural base or on top of an isolated layer changes both the wall and the floor. Masonry bearing on a resilient layer loads it along a line, and a wall built first with the build-up run up to it produces a different edge condition from one built afterwards. Which comes first is a design decision, not a sequencing one.
Read about Floating Screed Build-Up →A partition head above or below a ceiling line
A masonry partition taken to the structural soffit and one stopped at a ceiling look identical in the room and behave differently above it. Where it stops low, the wall the reader sees ends well below the wall the assembly needs, and the ceiling void runs over the top of a division that was built in solid units precisely because it was meant to be solid.
Read about Framed Board Ceiling →Where a partition runs into a separating construction
A heavy partition bonded or tied into a wall that divides occupancies is a continuous path into that wall. Whether the partition is stopped short, tied without bonding, or taken through belongs with the designer of the separating construction, because the decision is about the separating wall rather than about the partition.
Read about Separating Wall →Deciding what is buried and what is routed elsewhere
Every service that can be kept out of the masonry is a chase not cut. The coordination question is therefore which runs genuinely have to be buried and which can be taken through a ceiling, floor or riser zone instead, and it is resolved before the wall is built because afterwards the answer is a wall being cut.
Read about Service Void →Abutment with an external wall
An internal partition running into an external wall interrupts whatever continuous layers that wall carries. A masonry partition bonded into the inner leaf makes that interruption a permanent one, so whether the layers run past the partition or are joined to it is settled by the envelope designer rather than at the abutment.
Read about Air Barrier System →
Considerations
Topics worth discussing
Which topics genuinely apply to this system and what to raise about them. Measured values, classes and ratings come from a qualified professional's design for the specific building, not from a reference page.
- Movement
- This wall sits between a structure above it that will move and a structure below it that may move differently, and it is rigid. How much movement is expected at the head, and how long a run can be before a joint is introduced within it, are design judgements taken from the structural design rather than from the wall.
- Acoustic
- Mass is often the reason a masonry partition was chosen, but acoustic behaviour belongs to the complete assembly together with the flanking construction, the junctions and every service penetration. This entry states no values, and a chase or a back-to-back accessory can matter more than the wall itself. The question belongs with a qualified acoustic professional.
- Buildability
- The wall is built wet and heavy, in a sequence that has to fit around the floor beneath, the soffit above and the trades that follow. Chases are cut after the wall is up and before the finish goes on, which is a narrow window shared by everybody who needs something buried.
- Fire
- Internal masonry is frequently used where a division has fire duties, and those duties are a property of a complete, correctly detailed and correctly installed construction — including the head, the abutments and every penetration — determined by others. Nothing here states or implies any such performance.
- Durability
- A solid wall takes impact and fixings better than a hollow one, which is often why it is chosen, and it also has no forgiving zone. Damage at an arris, at a door head or from a fixing removes material, and the repair is made into the element rather than into a facing over it.
- Maintenance and access
- Anything buried in this wall is reached by breaking into it. Where a service might reasonably need replacing within the life of the building, whether it belongs in the masonry at all is worth raising while the route is still on paper.
- Documentation
- The positions of chases and of anything built into the wall are invisible once the finish is on, and unlike a framed partition there is no cavity anyone can look into later. A record made between the wall going up and the finish going on is the only record there will be.
Design
Questions the design has to answer
The decisions this assembly turns on. They are questions rather than answers, because the answer depends on the building.
- What is beneath this wall along its whole length, and was that construction arranged to receive a heavy line load?
- How is the head detailed so the wall is restrained without being loaded, and who has told the builder what that gap is for?
- Which services are being buried in the masonry, and which of them could be routed outside the wall instead?
- Does the partition run to the structural soffit or stop at a ceiling, and does anything in the brief depend on which?
- How long are the runs, and has anything been decided about movement provision within them?
- Where will something heavy later be fixed, and does the unit family chosen take that kind of fixing?
- Where the partition abuts an external wall or a separating construction, who is deciding whether it is bonded, tied or stopped?
Boundaries
Commonly misunderstood points
Distinctions that are easy to blur, and the places where a familiar term means something narrower than it sounds.
- A non-loadbearing wall is assumed to be a wall that has no structural consequences, when its own weight is the reason half of this system exists.
- The head gap is read as an untidy joint to be filled, when it is the detail that keeps the wall out of the load path of the floor above.
- A chase is treated as the equivalent of a cable run in a framed partition, when one occupies a void that was already there and the other takes material out of the wall.
- Because the finished faces are indistinguishable, a masonry partition and a framed one are assumed to be interchangeable in plan, when only one of them can be moved without asking about the floor.
- A masonry partition is sometimes assumed to be doing the job of a separating wall because it is heavy, when the two are designed against entirely different questions.
Conversations
Questions for qualified professionals
Bring these to the relevant qualified professional, manufacturer or authority. Requirements vary by project and location.
- Has the structure beneath this partition been checked for the load the wall will apply along its line?
- What movement does the structure above allow, and what head restraint detail has been specified for it?
- Where may chases be cut in this wall, in what direction, and where may they not?
- Is any fire or acoustic duty attached to this wall, and if so who has determined what the junctions and penetrations have to do?
- Should this be a masonry partition at all, or is a framed one being ruled out for a reason that still holds?
- How will the positions of buried services be recorded for the building owner?
What this page does not do
- This entry describes how the assembly is organised. It states no dimension, weight, span or movement allowance, and is not a specification for any particular wall.
- Fire and acoustic performance are properties of complete, tested and correctly installed constructions including their junctions, are determined by others, and none is stated or implied here.
- Whether a given floor can carry a masonry partition, and where that partition may stand, is a structural determination made by a qualified engineer.
- Cutting into an existing internal masonry wall, including chasing it, can affect an element that is holding itself up and may reveal a wall that is in fact carrying load; establish which before any work starts.
Related systems
How this system relates to others
Every link states what the relationship actually is, rather than leaving a bare list of related pages to be read as a suggestion.
Alternatives
Different systems answering the same need. Listing them together is not a comparison and does not suggest one is better — which, if either, suits a project is a design decision.
Commonly built alongside
Systems routinely present in the same building without a junction recorded between them and this one. Where two systems do meet, the junction is set out above instead.
Applications
Building contexts this system is used in
The functional parts of a building this assembly is commonly met in. This is membership, not a ranking and not a recommendation: several systems answer any one context, and which of them suits a project is a design decision. A context appearing here does not mean the system is suitable, permitted or adequate for it.
- Building Interior · Interior
- Internal Partition · Interior
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this assembly involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this system comes up.
Internal Partitions, Linings, Ceilings and Wet Areas
Internal elements whose behaviour comes from the framework, the void and the perimeter behind them rather than from the board or tile on the visible face.
Browse all partitions & linings entries →