How to prevent gable end staining

How to prevent gable end staining

Tom Woodhouse, site services manager at Marley, provides his top tips to prevent gable end staining

A few years ago, staining of the gable end wall was sometimes noticed on new or refurbished houses, caused by water shedding from inferior, incompatible or incorrectly fixed dry verge systems. As well as unsightly black staining and moss growth, this could also leave the gable wall saturated and at risk of frost damage.

Such was the concern about this, that when the new Dry Fix Standard, BS 8612, was introduced last year it included some strict tests for dry verge products. This means that a compliant system must not allow water to discharge in one or more concentrated, continuous or intermittent streams on the wall.

Gable end staining - high res

Therefore, staining to the gable end wall should really be a thing of the past. Yet, recently, there have still been occasional reports of incidences on new properties. This probably means that either a compliant system hasn’t been used, it isn’t compatible, or it hasn’t been fixed according to manufacturer instructions. For builders and roofers, this type of call-back can be costly, as not only will it mean repairs to the dry verge, but also to any damaged brickwork.

So how can you make sure the dry verge you are using won’t cause gable end staining? Here are our technical team’s top tips.

  1. Never use a dry verge system that is not BS 8612 compliant. This means that it hasn’t been tested to meet the minimum quality required by the British Standard.
  2. Choose a dry verge system that has an integral design feature to drain water away from the wall. For example, both our Ashmore and Universal Dry Verges have been designed and tested to protect against gable end staining, with multiple drainage channels to direct water away from the wall.
  3.  Always follow the manufacturer instructions. Even if you have fitted similar products before, check the instructions as failure to do so could lead to an inadequate fix or water shedding and invalidate any warranty. All verge tiles should be mechanically fixed in accordance with BS 5534 in addition to the use of the universal dry verge units, i.e. by nailing, clipping or screwing as appropriate.
  4. Having a continuous bargeboard can add further protection, by making sure the verge is positioned out from the brickwork. However, as part of BS 8612 requirements, our dry verge products are tested without a bargeboard present – so contractors can have peace of mind they will drain water effectively with or without a bargeboard.
  5. Minimise the risk of incorrect fixing by choosing a system that is simple to install to British Standards. For example, a dry verge system that includes a batten end clip makes the mechanical engagement required under BS 8612 much simpler. Our batten end clip has sharp teeth which grip into the batten, making it extremely secure, as well as being very quick to push or hammer into place. Unlike others on the market, it can be fitted after the roof has been tiled.
  6. Take extra care with eaves closure units, or starter verges, and always follow manufacturer instructions. Depending on the design, it can be particularly difficult to fix the eaves closure unit adequately.  This can lead to roofers having to improvise to gain a secure mechanical fix, using things like brick ties, to achieve a suitable fix into the fascia or roof substructure. To prevent this, our Universal and Ashmore Dry Verges incorporate a quick starter verge fixing method that can be installed easily, regardless of any obstructions such as gutters. This provides an easy-to-install, robust method of securing the first verge unit, even when there are no bargeboards. This also gives the site manager visual confirmation that the verge has been installed correctly.
  7. For refurbishment work, you need to make sure there are no undulations where the dry verge will be installed. Any roof dipping at the edges can cause excessive water run-off, so you may need to adjust the battens underneath to make it flatter.
  8. Compatibility is crucial. Many dry verge products are sold as universal but they have different levels of compatibility so it is important to check this. Our Universal Dry Verge is compatible with all three main interlocking tile types; large standard, medium format and large format thin leading edge. Our Ashmore Dry Verge has been designed to complement the Ashmore double interlocking plain tile but it is also fully compatible with other interlocking plain tiles on the market.

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