Drainage board and protection board: which goes where and how to fasten it
The library branch’s drainage roll has been hung using a fixing method copied from a plywood mock-up. Behind it is a completed foundation membrane. The foreman cannot confirm that the attachment or fabric orientation matches the approved assembly.
Read the approved assembly to establish which drainage and protection layers it requires, then check each layer’s orientation, connections and attachment method. They are not interchangeable labels for any board outside the membrane. The drainage source below describes a filter fabric and drainage core, while its installation guidance distinguishes attachment to waterproofing from attachment to other substrates. Do not copy a fastening arrangement from bare concrete or timber onto the membrane.
Check the layers as part of the complete wall
- Identify the actual layers. Trace protection, drainage, insulation and membrane on the current detail. Confirm the delivered grades and any specified backing. Ask the responsible technical people about an unclear substitution rather than deciding that one roll automatically replaces another layer.
- Confirm the orientation. Use the approved product instructions and assembly detail to identify the face against the membrane and the face toward the surrounding material. Mark that orientation on the crew’s sample; do not rely on the assumption that all dimpled products face the same way.
- Check the seam and edge details. Review how the actual system joins cores and closes fabric edges against soil entry. Retain the required continuity around changes of level and interruptions instead of ending the drainage layer wherever a roll becomes inconvenient.
- Trace the water’s intended outlet. Locate the approved collector and discharge connection on the drawings. Confirm who completes it and what must be reviewed while visible. A drainage board installed on the wall does not prove its outlet is connected or operable.
- Verify attachment compatibility. Bring the actual membrane, backing and proposed method to the responsible installer or technical contact. Follow the approved arrangement and record any damage for assessment and repair; an attachment suitable elsewhere may be unsuitable here.
- Record the covering handover. Check the required membrane, layer and connection records for the exact section. Agree its protection from following work and obtain the authorized covering release, keeping unresolved outlets or damaged areas visible as open items.
Common mistakes
- Treating all dimpled rolls as the same assembly.
- Copying fasteners from another substrate application.
- Covering a collector connection before its required check.
Checklist
Before the layers disappear under backfill
- Delivered layers match the approved assembly.
- Faces and seam details confirmed.
- Collector and discharge connections traced.
- Attachments compatible with the membrane.
- Damage, corrections and covering release recorded.
Check your understanding
The fixing worked on plywood. Does that prove it is suitable over waterproofing?
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