The extreme rules!

Klober develop underlay for low-pitch roofs that meets all the criteria of BS 5534:2014

Extensions and loft conversions are popular and cost-effective alternatives to moving house, providing an ongoing source of work for many roofers. How, when working to the new Standards of BS 5534:2014, can we make the most of these opportunities?

When working on these types of projects, contractors often have to identify a workable solution that blends in well with the rest of the property, whilst working with a roof pitch that is limited by existing windows or pipework. Using a matching natural slate or plain tile has always been out of the question, but thanks to Klober’s new underlay, Permo® Extreme RS SK2, you can now go well below minimum pitches. As low, in fact, as 12.5° with profiled tiles or 15° with flat tiles.


The Permo® Extreme RS SK2 gives you a number of key benefits:

  • Tear-resistant
  • Double, self-adhesive strips provide a permanent seal of laps
  • Immediate protection against wind driven rain or snow, when laid at a 15° pitch
  • Best laid onto 12mm ply board or OSB sarking board, so no draping between rafters

Permo® Extreme is extremely easy to use. Simply position the underlay and peel away the protective self-adhesive strips before pressing laps into place. Finish off by counter battening and, unless you are building a warm roof, ventilate at or near the ridge. Use Klober Butylon tape beneath the counter battens to seal around any nail penetrations, as such low pitches will lead to a certain amount of capillary action. Permo® Extreme will cause the water to drip from the top of the tile and be carried between the counter battens to the gutter.

By using Permo® Extreme, you can offer your customers total flexibility in the type of tile or slate they choose. It also means you can avoid having to use unsightly, large format concrete tiles that are not only unsuitable for small roofs, but also a poor match for the property’s existing tiles. Good news for both you and your client.