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CONCRETE JOINT & WATERSTOP TOOLS · FIELD TOOL

Waterstop Overlap Length Estimator

Each join between pieces, and each corner, uses one overlap. A 40 m joint in 5 m strips with 50 mm laps and 4 corners has 12 joins, 0.6 m of overlap (1.5%), so order 42.6 m with 5% waste. PVC waterstops are heat-welded end to end and have no overlap.

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Behind this panel: an example with the default sizes.

Inputs

Results update as you type.

Run
m
Product
m
mm
%
Waterstop pieces with overlaps9 pieces · 12 joinslap 50 mm at each join · order 42.63 mmyconstructioncalculator.comNot to scale
Diagram updates as you type.

Results

Check the working before you order.

Length to order
42.63m
Pieces / rolls9
Joins (incl. corners)12
Extra length in overlaps0.60 m (1.5%)

Follow the manufacturer’s detail for joins and corners; some strips are butted tight, not overlapped.

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Working
  1. Pieces along the run = ⌈(run − lap) ÷ (piece − lap)⌉ = 9
  2. Joins = 9 − 1 + 4 corners = 12; overlap length = 12 × 50 mm = 0.60 m
  3. Order = (run + overlaps) × 1.05 = 42.63 m
Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.
Formulas


Pieces     = ⌈(run − lap) ÷ (piece length − lap)⌉
Joins      = (pieces − 1) + corners
Overlap    = joins × lap
Order      = (run + overlap) × (1 + waste)


Worked Example


40 m of joint, 5 m hydrophilic strips, 50 mm overlap, 4 corners, 5% waste:


    

  1. Pieces = ⌈39.95 ÷ 4.95⌉ = 9
    2. 

  2. Joins = 8 + 4 = 12 → overlap = 12 × 0.05 = 0.6 m
    3. 

  3. Order = (40 + 0.6) × 1.05 = 42.6 m
    4. 



Overlap as Extra Length (50 mm laps, no corners)






Piece length
Extra length






2 m
2.6%




5 m
1.0%




10 m
0.5%






Frequently Asked Questions
How much should waterstops overlap?
Follow the manufacturer's detail. Hydrophilic and bentonite strips are often butted tightly or overlapped by a short length; steel plate waterstops are lapped; PVC waterstops are welded, never overlapped.
Do corners need an overlap?
Usually yes for strip products: either a lapped corner or a mitred, tightly butted corner as the manufacturer details. Plan one join per corner.
How much extra waterstop should I order?
The overlap length plus about 5% for offcuts and damage. Short pieces mean more joins and more overlap.
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