Polyethylene control layers: check supported laps, edges and penetrations
The crew has stapled polyethylene across a floor, but several laps have no visible record of their required connection. The foreman needs to check the actual detail and installed work before treating a smooth-looking sheet as a completed control layer.
Confirm what the polyethylene is assigned to do in this assembly. It may have a vapour-control function, and an approved sealed arrangement may also form part of air control. NRCan’s educational guidance emphasizes supported, sealed connections and attention to penetrations. The project’s actual sheet, sealant, backing and connection details govern the installation; staples and a tidy face do not independently establish every required seal.
Follow the connection through the sheet
- Confirm the current material and function. Check the approved assembly, sheet specification and actual product instructions. Identify whether the layer has one or more assigned control functions. Confirm compatible sealing materials and receiving conditions. Do not select a remembered sheet thickness, sealant tube or generic overlap dimension in place of the current requirements.
- Prepare the supported lap and edge details. Locate the specified backing, receiving surface and sealing arrangement before fixing the sheet. Follow the actual order and fastening instructions. Keep the connection accessible for its required check. Avoid using a tube count as proof of seal quality: purchased material does not show where a connection is continuous or whether its surfaces were suitable.
- Trace interruptions and changes of material. Check boxes, service penetrations, openings, partitions and floor lines against their actual details. Identify who makes each connection and when. Do not assume the sheet can simply stop at a projecting box or that batt material supplies the missing seal. Refer an absent or incompatible detail before inventing a tape patch or moving another trade’s work.
- Check and restore the installed layer. Use the agreed inspection method to compare laps, edges and transitions with their requirements. Record located defects and correction status while access remains available. Restore any inspected opening or later damage using the accepted method. Obtain the required review before concealment; a local test or neat repair does not certify every uninspected connection on the floor.
Common mistakes
- Calling every poly sheet both a complete air and vapour system.
- Stapling a lap without its specified connection.
- Using tube purchases as proof of continuous seals.
- Patching a transition without checking compatibility and the detail.
Checklist
Check the sheet’s actual connection record
- Specified material and assigned control function.
- Supported laps, edges and compatible sealing arrangement.
- Located interruptions and connection owners.
- Observed corrections and required restoration.
- Received pre-cover review and uninspected limits.
Check your understanding
The sheet is flat and well stapled. Does that establish its required sealed lap is complete?
