To fill and seal non-structural crack and cavities in structural concrete such as concrete decks, balconies, concrete roof structures, wet room, swimming pool and especially before waterproofing works. (TDS p.1)
- Pack
- 160 mL and 850 mL set
Step-by-step solution
Green roofs, roof gardens and planters
Roof gardens, landscaped decks and built-in concrete planters stay wet under soil for years, so the waterproofing must be done before any soil goes in. The data sheets we hold cover bitumen and cement-based layers; ask us about root barriers and dedicated green-roof systems.
- 5 steps
- 2 products
- 3 answers
You need this when…
- Damp on the ceiling below a roof garden or planter
- Leaks at planter corners or where the planter meets the slab
- Roots growing into cracks or joints
- Blocked drains and waterlogged soil
The work, step by step
General guidance based on the manufacturer data sheets. Site conditions differ: confirm the system with MCT before you start. Where we do not name a product, ask us and we will confirm the right one.
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Step 1: Check load and drainage first
Wet soil is heavy. The engineer must confirm that the slab can carry the planted build-up. Plan falls and accessible drain outlets that cannot be blocked by soil.
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Step 2: Prepare the slab and seal cracks
Clean down to sound concrete and fill non-structural cracks up to 10 mm in concrete at least 28 days old (Sikadur-20 Crack Seal p.1, p.2).
Sikadur-20 Crack Seal Sika Request a quotation -
Step 3: Apply the waterproofing layer
On landscape decks, use a bitumen emulsion in at least 2 coats (Sika Bitumen AE p.1, p.2), or a rubberised bitumen tanking emulsion in 2–3 coats (Sika Igasol Emulsion BA-6510 p.1, p.2). Inside planter boxes, a cement-based slurry can be used for water containment (SikaSeal-105 PK p.1, p.2). Carry the layer up the walls above the future soil level.
Sika Bitumen AE Sika Request a quotation Other options for this stepAsk us The right product here depends on your site. We confirm it before naming it.
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Step 4: Root protection
Root resistance is not stated in the data sheets of the coatings above. Root-resistant sheet membranes on file are listed for basements and cut-and-cover work and need Sika-trained installers (Sikaplan WT 1200-16 C p.1, p.3). Ask us for the root barrier.
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Step 5: Protection screed and joints
Where a screed protects the layer, blind the last bitumen coat with clean sharp sand to give a key (Sika Bitumen AE p.2). Seal floor joints that stay wet with a polyurethane floor sealant, primed as its data sheet requires for water immersion (Sikaflex PRO-3 p.1, p.4).
Product for this stepAsk us The right product here depends on your site. We confirm it before naming it.
Proposal brief
Green roofs, roof gardens and planters: scope and system
A starting point for a site proposal. Quantities, prices and the final specification follow a site visit or photos.
Scope of work
- Slab preparation and crack sealing on x m²
- Waterproofing layer with upstands above soil level
- Detailing at drains, planter corners and penetrations
- Protection screed
- Flood test before soil is placed (method to be agreed)
System build-up
| Step | Product | Pack | Source |
|---|---|---|---|
| 2. Prepare the slab and seal cracks | Sikadur-20 Crack Seal | 160 mL and 850 mL set | TDS p.1 · March 2025, Version 03.02 |
| 3. Apply the waterproofing layer | Sika Bitumen AE | — | TDS p.1 |
What we need from you
- Area of the roof garden and size of each planter
- Soil depth and planting plan (lawn, shrubs, trees)
- Drain positions and photos
- Engineer's confirmation of the slab load
Site conditions
- Engineer's sign-off on load
- Dry weather while coatings cure (Sika Bitumen AE p.2)
- Soil placed only after the waterproofing has been inspected
Not included
- Root barrier, drainage board and filter fabric (to be confirmed: ask us)
- Soil, planting and irrigation
- Structural strengthening
Questions customers ask
Will roots damage the waterproofing?
Ask us: it depends on site conditions. Root resistance is not stated for the coatings in this guide. Some sheet membranes on file state root resistance but are listed for basements (Sikaplan WT 1200-16 C p.1).
Can we use the white roof coating under soil?
No. Sikalastic-560 GCC is not for buried systems or constant water immersion (Sikalastic-560 GCC p.3).
How long before soil can go on?
Sika Bitumen AE is fully cured after about 72 hours (Sika Bitumen AE p.2). Allow time for inspection and a water test before backfilling with soil: ask us.
Steps and product facts are taken from the manufacturer data sheets (page cited). Products are named only where the data sheet confirms the use; quantities follow a site visit or photos. General guidance: check the data sheet or ask us before you start.