This parapet gutter is a good example of the complete solution to a fairly common issue with this type of gutter design.
Hard cement render had allowed water ingress to cause major cracking and frost damage to the coping stones and render finish.
The existing coping stones had severe spalling and advanced decay in terms of stone de-lamination.
Repairs were undertaken to the render finish and copings prior to lead cladding and capping to prevent further ingress of water.
In an ideal situation the copings would have been replaced, but after consideration and discussion with our client, our view was to conserve the existing rather than cause considerable damage to the fabric of the building, due to the exceptionally hard cement render finish.
On this project we took the decision to renew the gutter lining in code 7 milled lead sheet to ensure lifespan, cladding and capping was in code 6 milled lead sheet.
Central Valley Gutter, Bridge.
Lead sheet failure in valleys is most commonly caused by:
- Oversizing of lead sheet leading to fatigue cracking
- Inadequate falls or timber substrate failure
- Over-fixing fatigue cracking due to eaves tiles nailed though the lead upstand
- Poor gutter design and outlet sizes
- Incorrect step heights and splash laps, which can cause leakage through capillary action
This project required the complete renewal and reconstruction of the entire valley gutter timber substrate including some of the central oak wall plate, which was in a state of decay due to years of water ingress. Our initial task was to remove the existing lead and timber and inspect the level of damage to the building. Once the Oak plate had been replaced in sections, we rebuilt the gutter in treated soft wood boarding.
Softwood boarding with ventilation gaps is our preferred substrate as it is less likely to cause underside corrosion due to improved air-flow to the underside of the lead sheet.
It should be stressed that although boarding such as plywood is an acceptable substrate in terms of industry standards, our experience shows softwood boarding performs better.
Specific lead sheet underlays and adequate ventilation are also of utmost importance when working with historic buildings and modern insulation products.