Balcony and terrace - same material, different challenges
Composite decking works on both balconies and terraces. The technology is identical - joists, clips, WPC panels. But the installation conditions are vastly different. A balcony is a structure suspended above the ground, exposed to wind and limited by weight. A terrace is a large surface at ground level or on a roof, with its own set of challenges: drainage, substrate preparation, scale.
In this article, we compare both scenarios step by step - from the substructure, through water drainage, to costs and installation time. If you're wondering whether your space is a "balcony" or a "terrace" and what that means in practice - you'll find the answers here.
Definitions - what is a balcony, and what is a terrace?
Before we get into the technical details, let's clarify terms. In construction, these have specific meanings.
Balcony
A balcony is a cantilevered slab (or one supported by columns) projecting beyond the building outline, always above ground level. Typical features:
- Suspended structure - attached to the wall or floor slab
- Surface area usually 3 - 12 m2
- Limited load capacity (typically 250 - 400 kg/m2)
- Exposed to wind, rain, sun
- Access through the flat - materials transported through balcony doors
- Railing/balustrade legally required
Terrace
A terrace is a paved surface at ground level or on a flat roof. Typical features:
- Ground-level or rooftop structure
- Surface area usually 10 - 50+ m2
- Load capacity depends on the substrate (ground - virtually unlimited, roof slab - per structural design)
- Requires substrate preparation (levelling, drainage)
- Easy access - materials can be delivered directly
There's also the loggia - a recess within the building shell with a floor at apartment level. For installation purposes, we treat it like a balcony, except that it's more sheltered from wind.
At BalkonSetup we install composite floors on both balconies and terraces - ground-level and rooftop. The same joist system, the same boards, the same CNC precision. What differs is the substrate preparation and installation logistics.
Substructure - the fundamental difference
The way joists are mounted is the biggest difference between a balcony and a terrace. On a balcony, the substrate is a given - it's a concrete slab. On a terrace, you often need to prepare it from scratch.
Balcony - joists on tape, no drilling
On a balcony, we mount joists directly on the existing concrete slab. The substrate is usually level (or requires minimal correction). Key principles:
- Anti-slip tape under the joists - prevents the structure from shifting, doesn't damage the waterproofing
- No drilling into the slab - this is a fundamental rule. Drilling damages the waterproofing and can lead to leaks into the apartment below
- Joist spacing 25 - 30 cm - tighter than on a terrace, as a balcony requires stability over a smaller area
- Edge margin - boards don't reach all the way to the railing (7 mm gap), so water can flow freely off the edge
A complete installation on a 5 m2 balcony typically takes 3 - 4 hours. No chiselling, no pouring, no drilling.
Ground-level terrace - more substructure options
On a ground-level terrace, there are several ways to mount the joists:
- Joists on a concrete slab - same as on a balcony, the simplest and most stable option
- Adjustable pedestal supports - plastic or metal feet with adjustable height (3 - 20 cm). They level out an uneven substrate and create a drainage space
- Joists on spacer blocks - concrete or rubber pads under the joists, spaced every 40 - 50 cm
- Gravel base - a layer of compacted gravel with geotextile, on which joists are placed on supports
The choice of method depends on the substrate condition. A concrete screed is ideal. Bare ground requires preparation - geotextile (against weeds), a gravel layer and levelling.
Rooftop terrace - the highest requirements
A terrace on a flat roof combines the challenges of both a balcony and a ground-level terrace. The substrate is a roof slab with waterproofing - you can't drill into it (like a balcony), but the surface is large (like a terrace). Additionally, you need to consider:
- Waterproofing protection - adjustable supports with soft pads, no sharp elements
- Water drainage - the existing membrane slope must be maintained, roof drains must not be blocked
- Wind resistance - on higher floors, wind force is significantly greater, the structure must be appropriately weighted down
Water drainage - the critical issue
Managing rainwater is a topic that looks completely different on a balcony versus a terrace.
Balcony - slope to the edge
The balcony slab has a factory-set slope (1 - 2%) towards the outer edge. Rainwater flows through the gaps between boards onto the slab, and from there - to the drip edge and gutter, or simply drips off the balcony edge.
The composite system doesn't block this flow - 5 - 7 mm gaps between boards and the space under the joists ensure free drainage. On a balcony, drainage is straightforward because the surface is small and the slope was built in by the structural engineer.
Ground-level terrace - drainage is essential
On a 20 - 40 m2 terrace, water drainage is a completely different scale of challenge. Heavy rain on a 30 m2 terrace (at 50 mm/h intensity) means 1,500 litres of water per hour. It has to go somewhere.
Drainage solutions for terraces:
- Substrate slope - minimum 1 - 2% away from the building towards the garden/lawn
- Drainage channels - linear drains along the building wall or terrace edge
- Drainage layer - gravel under the joists channels water laterally
- Gaps between boards - as on a balcony, water passes through to below
- Ventilation space - 5 - 15 cm under the boards (on adjustable supports)
The key rule: water must never flow towards the building. The slope should always run from the house wall outward. Poor water management is the most common cause of terrace problems - not the surface itself, but what happens beneath it.
Rooftop terrace - existing drainage system
On a flat roof, the drainage system already exists - roof drains, internal gutters, membranes with built-in slope. Installing composite flooring must not disrupt it. Adjustable supports allow access to drains to be maintained (e.g. by creating removable inspection panels over key points).
Size and scale - how they affect installation
Surface area has a direct impact on installation planning, material quantities and labour time.
| Feature | Balcony (3 - 12 m2) | Terrace (10 - 50+ m2) |
|---|---|---|
| Installation time | 3 - 6 hours | 1 - 3 days |
| Board trimming | Proportionally more (balcony edges) | Proportionally less (economy of scale) |
| Material waste | 10 - 15% (more cuts) | 5 - 10% (longer boards, less cutting) |
| Material transport | Through the flat and balcony doors | Directly to the site |
| Substrate preparation | Minimal (concrete slab ready) | Often required (levelling, gravel, geotextile) |
| Shape complexity | Often non-standard (L-shape, trapezoid, curves) | Usually rectangular |
| Wind | Significant impact (3rd floor+) | Lower impact (ground level) |
Costs - balcony vs terrace
Material prices (boards, joists, clips) are identical - regardless of whether the installation is on a balcony or terrace. Cost differences arise from three factors:
1. Material cost per m2
On a terrace, material cost per square metre is usually slightly lower (by 5 - 10%) than on a balcony. The reason: raw materials are used more efficiently on a larger surface. 400 cm boards can be laid at full length without cutting, 300 cm joists are packed more efficiently by the cutting algorithm, and the waste-to-used-material ratio drops.
2. Substrate preparation
On a balcony, the substrate is ready - a concrete slab. On a ground-level terrace, you often need to:
- Level the ground (compaction, slope profiling)
- Lay anti-weed geotextile
- Spread a drainage gravel layer (5 - 15 cm)
- Possibly pour a concrete screed
That's an additional cost that doesn't exist on a balcony. Depending on substrate condition, it can range from several dozen to several hundred zlotys per square metre.
3. Labour time
Installation on a terrace is proportionally faster - less cutting, easier access, no need to carry materials through the flat. But a terrace is larger, so total labour time is longer. Per square metre, terrace labour is typically 10 - 20% cheaper than on a balcony.
Patterns and colours - are there differences?
Good news: there are none. The same range of boards works on both balconies and terraces. Available raw material lengths allow cutting to be optimised for any dimension.
The only recommendation relates to colours on rooftop terraces with heavy sun exposure: lighter shades (e.g. light oak or grey wood) heat up less than dark ones. On a balcony shaded by the floor above, this doesn't matter - but on an open south-facing terrace, it's worth considering.
The BalkonSetup system - one system, two applications
Our installation system is identical on balconies and terraces:
- LiDAR survey - precision scan of balcony or terrace dimensions (to 1 mm accuracy)
- Computer simulation - joist and panel layout designed in a dedicated simulator, with cut optimisation and waste minimisation
- CNC cutting - every board and joist pre-cut to size before installation, no on-site cutting
- Clip-based installation - no drilling, no adhesive, reversible system
The difference lies in the substrate preparation stage (on terraces) and material transport logistics (on balconies). The board installation itself follows the same process.
Frequently asked questions
Can I have the same pattern on the balcony and terrace?
Yes. All patterns are available for both applications. If you have a balcony and a terrace at the same house, we can install identical boards on both surfaces - a consistent look guaranteed.
Does a ground-level terrace need a concrete base?
Not always. If the ground is stable and well-drained, a layer of compacted gravel with geotextile and adjustable supports is sufficient. A concrete screed is a premium option - more stable and durable, but not essential.
Will composite flooring on a terrace survive winter?
Yes. WPC boards have water absorption below 1% and withstand multiple freeze-thaw cycles. On a terrace, where snow stays longer than on a balcony (because there's no heating from the flat below), this is particularly important. You don't need to remove the boards for winter or protect them in any way.
Which installation is faster - balcony or terrace?
Per square metre - a terrace is faster (easier access, less cutting). In absolute terms - a balcony, because it's simply smaller. A typical 5 m2 balcony takes 3 - 4 hours. A 25 m2 terrace takes 1 - 2 working days.
Summary
Balconies and terraces are two different installation environments, but composite flooring works in both. The key differences are:
- Substructure: balcony - joists on tape on a ready slab; terrace - adjustable supports, possibly a gravel base
- Drainage: balcony - factory slope, minimal intervention; terrace - requires planned slope and drainage system
- Cost per m2: terrace slightly cheaper (economy of scale), but substrate preparation adds cost
- Transport: balcony - through the flat; terrace - direct access
- Weight: matters on a balcony (though marginally), irrelevant on a ground-level terrace
Whether you're planning a floor for a balcony in an apartment block or a terrace by a house - check out our 22 board patterns and pick the one you like. The rest - survey, design, cutting and installation - is on us.
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