WATER BAR - FLAT ROLL
PVC Water Bar (Waterstop) – Flat Ribbed Roll
Stops water from leaking through the joints in your concrete. Cast it into the joint between two concrete pours and it creates a permanent, flexible seal inside the structure — ideal for water tanks, basements, swimming pools and retaining walls.
Product Overview
When concrete is poured in stages — a slab today, the wall tomorrow — a construction joint forms where the old and new concrete meet. That joint is the weakest point for water. Even good concrete will seep there under water pressure.
A water bar (also called a waterstop) is a flexible PVC strip placed across that joint before concreting. Half of it is cast into the first pour and the other half into the next pour. The ribs on its surface grip the concrete and make water travel a long, blocked path, so it cannot pass through the joint.
This is the flat, ribbed type in blue PVC, supplied in rolls so you can run it continuously along long joints with very few splices.
Specifications
| Product | Water Bar / PVC Waterstop – Flat Ribbed |
|---|---|
| Material | Flexible PVC (polyvinyl chloride) compound |
| Colour | Blue |
| Profile | Flat strip with raised anchoring ribs on both faces |
| Width | 230 mm (approx. 9") |
| Thickness | Approx. 6 mm |
| Roll length | 20 metres per roll |
| Joint type | Construction (non-moving) joints |
| Placement | Internal — cast in the centre of the concrete section |
| Splicing | Heat-welded butt joint (hot-plate / heat knife) |
| Resistance | Water, ground salts, mild acids and alkalis; does not rot |
| Minimum concrete thickness | At least 200 mm wall/slab recommended for a 230 mm bar |
| Price | KSh 25,500 per roll |
Key Features
Ribbed grip
Raised ribs lock firmly into the concrete and lengthen the water path.
Flexible PVC
Bends around corners and moves with small concrete shrinkage without cracking.
Long roll
20 m continuous length means fewer splices — fewer weak spots.
Heat-weldable
Ends fuse together with heat for a seal as strong as the bar itself.
Rot & chemical proof
Unaffected by water, soil salts and sewage — lasts the life of the structure.
Easy to cut
Cuts cleanly on site with a sharp knife or hacksaw.
Coverage Area
Water bar is measured by the length of joint (linear metres), not by square metres.
| 1 roll | Seals about 20 m of joint (less approx. 0.1–0.2 m for each weld/cut) |
|---|---|
| Tip | Add 5–10% extra for corners, offcuts and splices |
Example – underground water tank 4 m × 3 m:
Perimeter = (4 + 3) × 2 = 14 m of wall-to-base joint. Add 10% → about 15.5 m. 1 roll is enough.
If the walls are also poured in two lifts, add another 14 m for the second horizontal joint → about 31 m total → 2 rolls.
Benefits
- Leak-free structures — stops seepage at joints, the most common leak point in tanks and basements.
- Saves money long-term — far cheaper than breaking concrete and repairing leaks later.
- Protects steel reinforcement — keeps water away from rebar, preventing rust and concrete spalling.
- Permanent protection — sits inside the concrete, safe from sun, traffic and damage.
- Works under water pressure — suitable for below-ground and water-retaining structures.
- Safe for water tanks — inert PVC that does not dissolve or break down in stored water.
How to Install
- Plan the joints. Mark every place where concreting will stop and restart — usually where the base slab meets the walls, and between wall lifts.
- Measure and cut. Unroll the bar, let it lie flat in the shade to relax, then cut to length with a sharp knife or hacksaw.
- Position it centrally. Place the bar across the joint so that half the width goes into the first pour and half into the next. Keep it in the middle of the wall thickness, away from the steel cover zone.
- Fix it firmly. Tie the outer edges to the reinforcement with binding wire every 250–300 mm so it stays straight and doesn't fold during pouring. Only tie or nail through the outer edge — never punch holes in the centre.
- Splice by heat welding. Join two ends with a hot plate or heat knife: heat both ends until soft, press them together and hold until cool. Do not join with tape, glue or simple overlaps.
- Pour the first concrete. Pour carefully and vibrate well around the bar so no air pockets form under it. Keep the exposed half clean and straight.
- Prepare for the second pour. Before the next pour, clean the exposed bar of mud, oil and loose concrete. Roughen and wet the old concrete surface.
- Pour the second concrete. Pour and vibrate thoroughly around the second half of the bar. Cure the concrete properly (keep it wet for at least 7 days).
How to Use – Where It Works Best
Use this flat water bar at construction joints in any concrete that holds back or holds in water:
Underground water tanks Overhead concrete tanks Basement walls & slabs Swimming pools Septic tanks & soak pits Retaining walls Culverts & box drains Fish ponds & reservoirs Lift pits Sewage treatment works
For very wide expansion joints that move a lot, a centre-bulb waterstop is the better choice — ask our team.
Avoid These Mistakes
- Placing the bar off-centre or folded over — water finds the short path.
- Nailing or drilling through the middle of the bar.
- Joining pieces with tape or overlaps instead of heat welding.
- Poor vibration that leaves honeycomb concrete around the bar.
- Leaving the exposed half dirty or bent before the second pour.
Frequently Asked Questions
What is the difference between a water bar and a waterstop?
They are the same product. "Water bar" is the common name on Kenyan sites; "waterstop" is the engineering term.
How many rolls do I need?
Add up the total length of all joints in metres, add 10%, and divide by 20. Send us your tank or basement size on WhatsApp and we'll work it out for you.
Can I use it on an existing leaking wall?
No — a water bar must be cast in while concreting. For existing leaks, ask us about Sika crystalline or injection waterproofing.
Do you install it?
We are supply-only, but we can share contacts of experienced independent fundis.
Do you deliver?
Yes — same-day within Nairobi and next-day countrywide on request. Free pickup at our Rongai and Tuala branches.
Need help sizing your joints?
Shabbiri Hardware Kenya Ltd — trusted since 1990
Ongata Rongai (opp. Hashi Petrol Station) | Tuala (past Nazarene University), Magadi Road
Ask us on WhatsAppSpecifications
| Model | ROLL |
| Category | Waterproofing & Sealants |
| Availability | In stock |
| Sourced by | Shabbiri Hardware Kenya Limited |
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