Double lap roofing
A double lap in roofing terms refers to how much overlap there is between each layer of roof covering; tile, slate, shingle etc. A double lap is general the most common standard whereby each layer covers the layer beneath by about or less than half, so that two layers (double) overlap to create a water resistant roof cover.
Such roofs are laid from the eaves towards the ridge of the roof a row at a time, fixed into the roof battens with roofing nails. Roofing nails are short nails with a large flat round head to secure the slate or tile, and either a smooth or a corrugated shank for a more secure fixing.
Some roofing types such as scantile slate roofing found in Devon and Cornwall are laid to a triple lap, meaning each layer of slate covers a third of the slate beneath meaning three layers of slate (triple) overlap. This is considered to be more robust and weathertight for regions near the coast with high winds and salt water, with added resistance through the use of a lime mortar bedded between the slates and at the edges. A typical slate the might be used in this way is the Delabole slate which comes from Delabole quarry in Cornwall.
Because slate roofs are laid in this process with the next layer above covering the fixings of the layer below, acces to those fixings for repair or replacement can be difficult. As such many slaters or slate roofers will posses a slaters ripper or puller, which is a long thin tool (slightly longer than a slate) which can be inserted and slid from outside at the angle of the pitched of roof to rip the nail fixing the broken slate out.
[edit] Related articles on Designing Buildings
- Battens.
- Ceiling tiles.
- Ceramic tiles.
- Clovelly, a village changing hands and changing with the times.
- Conservation.
- Delabole Slate.
- Domestic roofs.
- Flashing.
- Flat roof defects.
- Heritage.
- Historic environment.
- IHBC articles.
- Institute of Historic Building Conservation.
- Nails - a brief history.
- Photocatalytic tiles.
- Pitched roof.
- Planning for sustainable historic places.
- Reconciling conservation and sustainable development.
- Roof coverings.
- Roof insulation.
- Roof slates.
- Roof tiles
- Roofing defects.
- Shingle roofing.
- Sustaining Clovelly, a history, its management and retrofit.
- Thatch roofing.
- Tiles.
- Tile roofing
- Types of nails.
- Types of roof
- Weatherboarding
Featured articles and news
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
New-style degrees set for reformed ARB accreditation
Following the ARB Tomorrow's Architects competency outcomes for Architects.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.
Preserving, waterproofing and decorating buildings.
Many resources for visitors aswell as new features for members.
Using technology to empower communities
The Community data platform; capturing the DNA of a place and fostering participation, for better design.
Heat pump and wind turbine sound calculations for PDRs
MCS publish updated sound calculation standards for permitted development installations.
Homes England creates largest housing-led site in the North
Successful, 34 hectare land acquisition with the residential allocation now completed.
Scottish apprenticeship training proposals
General support although better accountability and transparency is sought.
The history of building regulations
A story of belated action in response to crisis.
Moisture, fire safety and emerging trends in living walls
How wet is your wall?
Current policy explained and newly published consultation by the UK and Welsh Governments.
British architecture 1919–39. Book review.
Conservation of listed prefabs in Moseley.
Energy industry calls for urgent reform.
Heritage staff wellbeing at work survey.