When installing plumbing and heating systems, running plastic pipework through timber joists requires precision, compliance with structural regulations, and careful protection of the materials. Whether you are working with flexible plumbing systems or rigid runs, getting the installation right prevents potential noise, abrasion, or structural compromise.
In our latest installation video, our category manager walks through the essential four-step process for successfully running our Pro-Straight® Plumbing and Heating pipes through joists.
Below is a comprehensive guide detailing these best practices for professional installers.
Step 1: Drilling the Joists Correctly
Before routing any pipework, you must drill the joists in compliance with structural guidelines regarding hole positioning, diameter, and spacing to maintain the structural integrity of the floor.
- Hole Location: Always drill homes on the neutral axis (the centre line) of the joist, as this area experiences the least structural stress.
- Clearance and Sizing: Utilise a suitable hole saw to ensure sufficient clearance for the pipe to pass through freely without binding.
- Spacing Rules: Make sure you consult Building Regulations for full guidance on safe distances from supports.
Step 2: Checking for Sharp Edges and Debris
Once the joists are drilled, preparation is critical to prevent any damage to the pipework.
- Inspect the Bores: Thoroughly check each drilled hole for splinters, burrs or rough wooden edges left behind by the hole saw that could potentially scratch or score the exterior of the pipe as it is pulled through.
Step 3: Running the Pipe Safely
When pulling flexible polybutylene pipes through multiple joists, some care must be exercised to prevent any potential abrasion, or structural compromise.
| Tip: When feeding the pipe through consecutive joist holes, take your time to pull the pipe smoothly. Avoid dragging the pipe sharply across unshielded/sharp timber edges to eliminate risk of surface scratching. Cover the end of your pipe with tape when running it through joists and floorboards to protect it from any damage and prevent debris from entering the pipe. |
Step 4: Lagging, Labelling, and Acoustic Protection
The final stage of a professional installation involves protecting the pipework from any potential physical friction, or potential acoustic transmission.
Insulation and Lagging:
Place insulation or lagging around the pipe where it passes through the joist hole. This acts as a protective buffer against friction and dampens any acoustic transmission down the pipe.
Preventing Pipe-on-Pipe Contact:
Where pipes cross over or run closely parallel to each other, always apply insulation pieces between them to stop any direct contact and rubbing.
Label Pipework:
There are several ways to label your pipework to indicate your hot and cold pipes: you could use red or blue pipe clips, or you could use identification tape.
For more detailed information on installing PolyPlumb® Enhanced products and our full range of piping systems, check out our Plumbing and Heating Installation Guide or subscribe to the PolypipeTrade YouTube Channel for more video demonstrations.
Summary of Best Practice Guidelines
| Installation Stage | Key Action | Primary Benefit |
| 1. Drilling | Drill on the neutral axis with sufficient clearance. | Preserves structural integrity of timber joists. |
| 2. Inspection | Check the drilled holes and remove any sharp edges. | Prevents potential for scratching when pulling pipe through joists. |
| 3. Pipe Running | Carefully feed Pro-Straight® pipe through joists. | Protects pipe surfaces and ensures seamless installation. |
| 4. Lagging | Apply insulation between pipes and drilled joists. | Isolates movement and protects from any potential acoustic transmission. |