The shower hob — also called the shower threshold, kerb, or step — is a raised barrier at the entrance to a shower recess that prevents water from flowing out onto the general bathroom floor. It is one of the most critical components in the shower waterproofing system, and it is also one of the most common failure points.
At Waterproofing Sydney, we connect homeowners with licensed contractors who understand that correct hob construction and waterproofing is essential for a leak-free shower. This guide covers everything you need to know about shower hob waterproofing for Sydney bathroom renovations.
What Is a Shower Hob and Why Does It Matter?
A shower hob is a low wall or step that forms the boundary between the shower recess and the rest of the bathroom. Under Australian Standard AS 3740-2010, the shower hob serves a specific purpose: it contains water within the shower recess, preventing it from flowing across the bathroom floor and potentially out through doorways or into adjacent rooms.
AS 3740 Requirements for Shower Hobs
- The finished height of the hob (after tiling) must be a minimum of 5 mm above the finished floor level outside the shower recess
- The hob must be waterproofed on all surfaces — top, inside face, outside face, and all junctions with the floor and walls
- The waterproofing membrane must be continuous from the shower floor, up and over the hob, and down the external face — no breaks or gaps in the membrane at any point
- Where the hob meets the shower side walls, the membrane must be continuous from the wall, across the hob, and into the shower floor
The 5 mm minimum height may seem small, but it is measured from the top of the finished tile surface outside the shower. In practice, the structural hob (before tiling) is typically 40–80 mm high to allow for tile and adhesive thickness on top.
Types of Shower Hobs
| Hob Type | Construction | Typical Height (structural) | Best For |
|---|---|---|---|
| Mortar hob | Sand and cement mortar formed in situ | 50–80 mm | Custom showers, most common in Sydney renovations |
| Brick hob | Single course of bricks laid on the slab | 76 mm (standard brick height) | Traditional construction, strong and stable |
| Pre-formed hob | Polystyrene or foam core with cement coating | 40–60 mm | Lightweight construction, fast installation |
| Tile trim hob | Metal or PVC tile trim profile at the shower edge | 10–20 mm | Minimal visual profile, semi-hobless appearance |
| No hob (hobless) | No physical barrier — water contained by floor falls and drainage | 0 mm | Accessible design, modern aesthetics |
Mortar Hob Construction
The mortar hob is the most commonly used shower hob type in Sydney bathroom renovations. It is built using a sand and cement mix formed to the required dimensions directly on the concrete slab.
Step-by-Step Construction
- Mark the hob position: The hob is positioned at the front edge of the shower recess. Ensure it aligns with the shower screen (if used) and the overall bathroom layout.
- Prepare the slab: The slab surface where the hob will sit must be clean and roughened (scored or ground) to ensure a strong bond between the mortar and the concrete.
- Form the hob: Using a 3:1 sand-to-cement mortar mix (or pre-mixed mortar), form the hob to the required dimensions. Typical dimensions are 80–100 mm wide and 50–80 mm high.
- Key into walls: Where the hob meets the side walls of the shower, the mortar should be keyed into the wall surface for a strong connection. Do not simply butt the hob against the wall — it will separate over time.
- Shape the top: The top of the hob should be flat or very slightly crowned (higher in the centre) to shed water back into the shower rather than allowing it to pool on top of the hob.
- Allow to cure: The mortar hob must cure for a minimum of 24 hours (ideally 48–72 hours) before waterproofing membrane is applied. Applying membrane to uncured mortar can cause adhesion failure.
Critical Construction Points
- The hob must be built on a clean, dry slab — not on top of existing tiles or over the waterproofing membrane
- The hob must be solid throughout — no voids, gaps, or loose material within the mortar
- The hob must be dimensionally stable — it should not flex, rock, or move when pressure is applied. Any movement will eventually crack the membrane and tiles.
- The hob width must be sufficient to support tiles on the top surface (minimum 60 mm is recommended, wider if using large tiles)
Waterproofing the Shower Hob
Waterproofing the hob is the most technically demanding part of the shower waterproofing process. The membrane must navigate multiple changes of plane — horizontal to vertical (floor to hob face), vertical to horizontal (hob face to hob top), and back to vertical and horizontal again on the outside face.
Step-by-Step Hob Waterproofing
- Prime all hob surfaces: Apply the membrane manufacturer’s recommended primer to the top, both faces, and all junctions of the hob. Allow the primer to dry fully.
- Install bond breaker tape at the inside base: Apply bond breaker tape along the junction where the shower floor meets the inside face of the hob. Embed the tape in a wet coat of membrane.
- Install bond breaker tape at the outside base: Apply bond breaker tape along the junction where the bathroom floor meets the outside face of the hob.
- Install bond breaker tape at hob-to-wall junctions: Where the hob meets the shower side walls, apply tape at the junction. This is a complex three-way junction and requires careful attention.
- Install bond breaker tape at the inside top edge: Apply tape along the junction where the inside face of the hob meets the top of the hob.
- Install bond breaker tape at the outside top edge: Apply tape along the junction where the outside face of the hob meets the top of the hob.
- Apply first coat of membrane: Apply the membrane in a continuous layer from the shower floor, up the inside face of the hob, across the top, and down the outside face to meet the bathroom floor membrane. There must be no break in the membrane anywhere on the hob.
- Allow curing: Wait for the first coat to cure according to the manufacturer’s specifications.
- Apply second coat: Apply the second coat using the cross-coat technique. Ensure adequate DFT on all surfaces, including vertical faces (where membrane tends to run thinner due to gravity).
Common Hob Waterproofing Mistakes
- Breaking the membrane at the hob top: Some applicators stop the shower floor membrane at the inside base of the hob and start a separate membrane on the outside. This leaves a gap at the top of the hob — the most vulnerable point. The membrane MUST be continuous over the hob.
- Insufficient membrane on vertical faces: Gravity causes liquid membrane to flow downward on vertical surfaces, resulting in thinner coverage. Apply the membrane more generously on the hob faces and check for thin spots.
- No bond breaker tape at hob junctions: Every junction on the hob involves a change of plane. Without bond breaker tape, the membrane will crack at these junctions as the building settles and undergoes thermal movement.
- Waterproofing over uncured mortar: If the mortar hob has not cured sufficiently, moisture from the mortar can prevent the membrane from adhering properly. Allow minimum 24 hours curing (48–72 hours is better).
- Hob not keyed into walls: A hob that is simply butted against the wall can separate, creating a gap in the waterproofing. The hob must be physically keyed into the wall surface.
Hobless Shower Waterproofing
Hobless (also called step-free, barrier-free, or walk-in) showers have become increasingly popular in Sydney bathroom renovations, driven by both aesthetic preferences and accessibility requirements. However, removing the hob introduces specific waterproofing challenges.
How Hobless Showers Contain Water
Without a physical barrier, water containment relies entirely on floor falls and drainage:
- Floor gradient: The shower floor must slope toward the drain at a steeper gradient than a hobbed shower — typically 1:60 to 1:80 near the shower threshold
- Linear drain at threshold: A linear (channel) drain positioned at the shower entrance intercepts water before it can flow onto the bathroom floor. This is the most common solution in Sydney.
- Recessed shower floor: The shower floor is set slightly lower than the surrounding bathroom floor (typically 10–15 mm), creating a shallow step-down that contains water. This is technically a “semi-hobless” design.
- Full room waterproofing: In some designs, the entire bathroom is treated as a wet zone with the floor graded toward the shower drain. This requires waterproofing the entire room to shower-level standards.
AS 3740 Requirements for Hobless Showers
AS 3740 permits hobless shower designs but requires alternative water containment measures. The standard specifies that water must be contained within the shower zone and directed to a floor waste. Your waterproofer and certifier must agree on the containment method before work begins.
Waterproofing Considerations for Hobless Showers
- The waterproofing membrane must extend across the entire bathroom floor — there is no hob to define the boundary between the shower zone and the general bathroom floor
- The membrane must extend up all walls to the required heights (1,800 mm on shower walls, 150 mm on other walls)
- Floor falls must be precise — hire an experienced tiler and waterproofer who regularly work with hobless designs
- The linear drain or threshold drain must be waterproofed as a continuous part of the floor membrane system
- Door thresholds require careful detailing to prevent water escaping under the bathroom door
Shower Hob and Screen Coordination
If your shower includes a glass screen or door, the hob and screen must be coordinated during the design and waterproofing stages:
- The hob width must be sufficient to support the screen channel or brackets (typically minimum 80 mm for most screen systems)
- Screen fixings that penetrate the hob must NOT penetrate through the waterproofing membrane. Use surface-mounted screen systems where possible.
- If screen fixings must penetrate the hob, the penetration points must be sealed with compatible sealant and the membrane repaired around each fixing
- Discuss screen placement with your waterproofer BEFORE the membrane is applied — retrofitting screen fixings through a completed membrane is problematic
Shower Hob Waterproofing Costs
| Hob Type | Construction Cost | Waterproofing Cost (included in shower waterproofing) | Total Additional Cost |
|---|---|---|---|
| Mortar hob (standard) | $150 – $300 | Included in shower waterproofing quote | $150 – $300 |
| Brick hob | $200 – $400 | Included in shower waterproofing quote | $200 – $400 |
| Pre-formed hob | $100 – $250 | Included in shower waterproofing quote | $100 – $250 |
| Hobless design (linear drain) | $300 – $800 (drain cost) | Additional $200 – $500 for extended floor waterproofing | $500 – $1,300 |
Note that the hob waterproofing itself is typically included in the overall shower waterproofing quote. The costs above represent the additional cost of hob construction or (for hobless designs) the alternative drainage and extended waterproofing required.
Inspection and Compliance
The shower hob waterproofing is inspected as part of the overall shower waterproofing inspection. Your building certifier or the waterproofer’s own quality check should verify:
- Hob height meets the minimum 5 mm above finished floor level outside the shower (measured after tiling)
- Membrane is continuous from the shower floor, over the hob, and onto the bathroom floor
- Bond breaker tape is installed at all hob junctions
- No gaps, tears, or thin spots in the membrane on any hob surface
- The hob is structurally stable with no movement or flex
- The hob-to-wall junctions are properly waterproofed with no gaps
The flood test (minimum 24 hours) validates the entire shower waterproofing system, including the hob. If the flood test fails, the hob junctions are among the first places to check for leaks.
Repairing a Leaking Shower Hob
If an existing shower hob is leaking, the repair options depend on the severity and cause:
- Minor leak at grout lines: Re-grouting and re-sealing the hob tiles may resolve the issue if the underlying membrane is intact. This is a temporary measure — if the membrane has failed, re-grouting will not fix the problem permanently.
- Membrane failure at hob junction: This requires removing tiles from the hob and adjacent areas, stripping the failed membrane, repairing the substrate, re-waterproofing, flood testing, and re-tiling. This is effectively a partial bathroom renovation.
- Structural hob failure: If the hob itself has cracked, separated from the wall, or become unstable, it must be demolished and rebuilt from scratch before re-waterproofing.
Hob repairs are among the most common waterproofing remediation jobs in Sydney, particularly in apartments built during the 2000s and 2010s in areas like Zetland, Waterloo, Mascot, and Olympic Park. Many of these buildings have experienced widespread waterproofing failures, with hob junctions being the most frequent failure point.
Frequently Asked Questions
What is the minimum shower hob height in Australia?
Under AS 3740, the minimum finished height of the shower hob is 5 mm above the finished floor level outside the shower recess. This is measured from the top of the tile surface outside the shower to the top of the tile surface on the hob. In practice, the structural hob (before tiling) is typically 40–80 mm high to account for tile and adhesive thickness.
Can I remove the shower hob and go hobless?
Yes, you can convert from a hobbed to a hobless shower, but it requires careful planning. You will need a linear drain or alternative water containment system, precise floor falls, and extended waterproofing across the bathroom floor. This is a significant modification that requires a licensed waterproofer and should be discussed with your building certifier. The entire bathroom floor must be re-waterproofed as part of the conversion.
Why do shower hobs leak?
The most common causes of shower hob leaks are: membrane discontinuity at the hob top (the membrane was not applied continuously over the hob), missing bond breaker tape at hob junctions causing the membrane to crack, the hob separating from the wall due to poor construction, and deteriorated grout or silicone on the hob tiles allowing water to reach the membrane. Hob junctions are high-stress areas due to the multiple changes of plane, making them inherently vulnerable if not waterproofed correctly.
Do I need a shower hob if I have a shower screen?
A shower screen alone is not a substitute for a shower hob under AS 3740. The screen prevents most water from splashing out of the shower, but the waterproofing system must still include either a hob or an approved hobless water containment solution (such as a linear drain). Water can and does get past shower screens — through gaps at the edges, under the screen channel, and through condensation runoff.
How wide should a shower hob be?
A shower hob should be a minimum of 60 mm wide to properly support tiles on the top surface. If a shower screen will be mounted on the hob, increase the width to at least 80–100 mm to accommodate the screen channel or brackets. Wider hobs (100–120 mm) provide more stability and are easier to waterproof due to less acute angles at the top edges.
Need expert shower hob waterproofing for your renovation? Get 3 free quotes from licensed Sydney waterproofers who specialise in shower hob construction and waterproofing. Waterproofing Sydney connects you with contractors who get hob detailing right the first time.
For related information, read our complete guide to shower waterproofing or explore our shower waterproofing services across Sydney.