As the NHBC issues new technical guidance on installing dry verge systems, Marley Eternit gives advice on how to overcome common fixing problems.
Following growing concern that some dry verge systems aren’t being fitted correctly, the NHBC has issued new technical guidance to try and reduce the amount of claims under its warranty. So, what’s the problem? Surely, the point of dry verges is that they should be easy to install? The issue is that, as with all dry fix systems, not all products available on the market have the same levels of compatibility or ease of fitting and this can cause problems.
The NHBC has identified a number of fixing concerns:
Problem – Eaves closure unit
The eaves closure, or starter verge, should secure the first unit at the eaves and cover the exposed end for an attractive finish.
Depending on the design, it can be particularly difficult to fix the eaves closure unit adequately. The NHBC claims department has seen numerous instances where these have become dislodged and, in some instances, impacted on the stability of the intermediate dry-fix verge units.
This is backed up by our own research with roofers, which shows that a lot of them dislike the starter verge fixing methods that many manufacturers provide.
A number of common reasons were cited, ranging from general over-complexity, lack of visibility when installing, through to the general misconception that the verge will be installed before the gutter, which often isn’t the case and causes an obstruction.
Solution
The NHBC states that in the majority of cases, manufacturers have specific instructions for securing the eaves closure unit and these should be followed, or if unsure then you should seek clarification from the manufacturer.
Yet, our own investigations have shown that roofers sometimes struggle to fit the eaves closure units according to the manufacturer’s instructions.
This means they end up 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 help overcome these problems, we have developed a brand new Universal Dry Verge system, which incorporates a new quick starter verge fixing method that can be installed easily, regardless of any obstructions such as gutters.
We’ve designed and developed this in conjunction with roofers to provide an easy-to-install, robust method of securing the first verge unit, even when there are no bargeboards.
The new fixing method, which incorporates a pivoting bracket, also provides visible evidence of a correct mechanical fix.
Problem: Fixing of intermediate dry verge units
The NHBC has identified a number of reasons for product failure, including tile battens not extending far enough beyond the outer edge of the wall, or bargeboard and inadequate fixings. It warns that this may lead to failure of the dry verge system, caused by imposed wind loads and wind uplift.
Solution
The NHBC recommends that you follow the manufacturer’s fixing instructions and make sure the dry fix systems and tiles are compatible.
Compatibility is crucial – while many dry verge products are sold as universal, until now none have been compatible with all three main interlocking tile types; large standard, medium format (15in. by 9in.) and large format thin leading edge.
We have designed our new Dry Verge with a unique internal rail system and leading edge hinge, so that it can be used with the majority of popular interlocking tile types from any manufacturer.
When doing retrofits, sometimes the tile battens don’t extend far enough beyond the wall. One solution is to use our Dry Verge Refurbishment Kit, which includes batten extension brackets.
Problem: Gable wall staining
A common problem, which particuarly affects some of the cheaper systems, is water leaking out of the verge and getting blown back onto the gable end, causing moss growth and staining.
The NHBC has warned that as well as staining, it can leave the gable wall saturated and at risk of frost damage.
Solution
The NHBC recommends that the dry verge system should either:
– Be positioned off the wall (e.g. tile batten overhang)
– Have an integral design feature (e.g. nibs) that keeps the verge unit away from the wall
– Have an integral design feature (e.g. drainage channels) that diverts water away from the wall.
As with our original dry verge product, our new system continues to include drainage features which help correctly channel rainwater to prevent this gable end staining.
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