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BLM Unislates provide complete weatherproofing where flue pipes and soil stacks penetrate a slate or profiled roof tile. 
The Unislate has a conical upstand and is manufactured from Code 4 Rolled Lead Sheet. It suits 100mm - 125mm outside pipe diameters and designed for roof pitches between 30° - 40°.
  • Provides weathertight joint
  • Effective in providing a weathering for pipes penetrating profiled tiles
  • Saves welding
  • No maintenance required
  • Unislates may be fitted in place when tiles are being laid and before the flue pipe is installed
  • Ensure that slates/tiles are fitted closely to the soil pipe
  • Apply Patination Oil to prevent unsightly carbonate from staining adjacent materials
  • Base dimensions: 550mm x 480mm - minimum upstand 150mm
  • Pipe sizes: 100 – 125mm outside pipe diameter

Unislate ‘How To’ Video Transcription

Below is a transcription of a video shot by BLM with Tim Fuge, Young Leadworker of the Year 2016, on the correct way to install Unislates.
Tim Fuge:
Hi, my name is Tim Fuge and we're here at the LSTA Training Centre in Kent to bring you the latest BLM guide to installing Unislates.

Why Install Unislates on a Roof

Tim Fuge:
BLM Unislates provide a weather-tight joint where a pipe penetrates a slate or tile roof. They're most suitable for use with profiled roof tiles. Unislates are made from British Standard Code 4 Lead, with a larger base size of 540mm by 480mm, allowing the edges to be dressed into the deepest part of the tile. The conical shape upstand measures 150mm at the back, which can be cut to suit outlet diameters between 100mm to 125mm, or 4" to 5". They suit roof pitches ranging between 30 to 40 degrees. For preparation, we first need to find the pitch of the roof to ensure we're using the correct slate. In this example, our pitch is 34 degrees. Our pipe has an outside diameter of 110mm.

Tim Fuge:
Unislates can be fitted in place prior to the pipe being installed. At this point, a good tip is to apply one of BLM's surface treatments to the reverse side of the Unislate, to prevent white carbonate runoff onto adjacent materials. Shake the container and apply with a clean, soft cloth and allow to dry. This avoids having to turn up the apron later to apply the treatments.

How to Install Unislates on a Roof

Tim Fuge:
A welted check-edge should be detailed along the top edge of the slate base to prevent any driven rain bypassing the top of the slate in storm conditions. The Unislate is then placed over the pipe and into position. Apply BLM Patination Oil with a clean, soft cloth to the surface, leading edges, and if you didn't pre-oil the reverse side prior to installation, the underside of the slate to a depth of 75mm. This gives the Lead a consistent dark-grey appearance and prevents staining.

Tim Fuge:
Roof tiles should be fitted as close to the pipe as possible. Plastic collars can be secured using solvent cement and finished off with a vent cowl.

Tim Fuge:
If you require further information, then please visit or Thanks for watching, and don't forget to check out more videos from BLM on YouTube, or via the free BLM app available to download from your app store.
To learn more best practices when it comes to leadwork use the links below to download the BLM app

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Full description of the product can be found on the download below:

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