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04/02/2019 1 Flat Roofing & Defects George Broll & Dougie Mabon UK’s largest roofing trade association, representing 70% of roofing industry. Over 125 years old. Acts as the voice of the roofing industry in the UK. Proactive in ensuring members offer high standards of workmanship and business practices - strict code of practice and independent vetting procedure, includes site inspections. Members include heritage specialist roofers and trained and reputable solar installers. Provide technical support for members and their clients. NFRC can deliver a series of seminars for surveying practices on ‘Traditional Roof Slating’, ‘The Use of Lead on Traditional Buildings’, ‘Flat Roofing’ and ‘Roof Sheeting and Cladding’. National Federation of Roofing Contractors (NFRC)
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& o Z } } ( ] v P ( ' } P } o o } µ P ] D } v · 2019-02-04 · Z u u v µ ] v P ] v ( o o À v X d Z } v v ] } v o À o } ( v ] o Z v Z } ( } µ v ] v } o u ] v o Á X 12[ SROOXWLRQ

Jul 14, 2020

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Page 1: & o Z } } ( ] v P ( ' } P } o o } µ P ] D } v · 2019-02-04 · Z u u v µ ] v P ] v ( o o À v X d Z } v v ] } v o À o } ( v ] o Z v Z } ( } µ v ] v } o u ] v o Á X 12[ SROOXWLRQ

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Flat Roofing & DefectsGeorge Broll & Dougie Mabon

► UK’s largest roofing trade association, representing 70% of roofing industry.

► Over 125 years old.

► Acts as the voice of the roofing industry in the UK.

► Proactive in ensuring members offer high standards of workmanship and business practices - strict code of practice and independent vetting procedure, includes site inspections.

► Members include heritage specialist roofers and trained and reputable solar installers.

► Provide technical support for members and their clients.

► NFRC can deliver a series of seminars for surveying practices on ‘Traditional Roof Slating’, ‘The Use of Lead on Traditional Buildings’, ‘Flat Roofing’ and ‘Roof Sheeting and Cladding’.

National Federation of Roofing Contractors (NFRC)

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Flat Roofing - Agenda

• The 4 main types of flat roofing systems • Repair & Maintenance• Safe use of Heat• Carbon Capturing in modern flat roofing

systems• Guarantees• NFRC and what it does

Different Types

• Mastic Asphalt• Reinforced Bitumen Membranes• Liquid Applied Membranes

including GRP• Single Ply Membranes, Rubber, PVC

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Mastic Asphalt• Hot Mixed on site

• No seams or laps

• Often used in Balcony situations

• Can be painted, chipped or left plain

• Robust Material - resistant to mechanical damage

• Life Expectancy in excess of 30 years

• Generally suitable substrate to be overlaid

• Very Hard Wearing

• Relatively Expensive

• Lack of availability of trained installers

Bitumen Felt• Modern Membranes can be applied with low heat and no

flame if fire risk is a consideration• Normally Mineral Granular finished – Different colours

available• Generally laid in sheets of 1 metre wide – visible laps• Life expectancy in excess of 30 years• Robust Material - resistant to mechanical damage• Granular mineral finish offers degree of grip for pedestrian

traffic (walkways should always be installed where regular traffic is envisaged)

• Degree of options for warranty 10, 15 or 20 years• Can be repaired easily by professionals• Ideal for refurbishment situations as the roof can be made

watertight by applying 1st layer• Not ideally suited for roofs with multiple projections, pipes

etc• Ease of installation & availability of material from Builders

merchants often results in “shoddy” work when applied by non trained persons

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Liquid Applied Membranes• Generally gives an almost seamless appearance

• A good choice in situations of multiple protrusions through the roof or where plant sited on it

• Available in different colours

• Can incorporate hard wearing anti-slip finish – suitable for balconies and walkways

• Not always suited to application in the Scottish Climate!

• In refurbishment situations, layer of felt may need to be applied first to maintain building watertight

Single Ply membranes

• Aesthetically pleasing

• Can give a decorative finish to mimic copper or lead

• Suitable to be used as a warm roof with insulation directly underneath

• Generally, usually only available through a network of approved installers. Good standard of workmanship should be expected.

• Manufacturer warranties should be given with most installations covering both materials and workmanship

• Not a very robust material. For foot traffic the roof must be protected by a walkway membrane or slabs

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Common Problems

• Lack of maintenance• Faulty installation• Time expired membranes• Incorrect detailing• Identification of defects

Maintenance

• Blocked rainwater outlets - Water will inevitably enter the waterproofing system

• Lack of Maintenance may invalidate warranty – Essential to follow manufacturer’s guidelines on maintenance and keep a record

• Flat Roofs should be cleaned at least twice a year but 2-3 times in areas of high leaf drop, pine needles etc.

• Check for signs of previous repairs, indicating previous water ingress• Regular inspections will show up signs of mechanical damage and

faults in general• Control access to the roof to prevent damage from follow on trades

e.g aerial installers, M&E teams etc

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Faulty Installation

• Air Blisters – Tacky when pressed. Can be cut out and repaired fairly easily and overlaid.

• Water blisters – Water has entered the system. Can be repaired provided the route cause is identified. In extreme cases the roof may need to be stripped and recovered.

• Faulty terminations to abutments. Cover flashings not properly installed or sealed

• Abutting walls may be faulty. Cracked render can cause water ingress into flat roof systems.

• Faulty Installation will usually manifest within 1-2 years of installation

Time Expired Membranes

• Most Modern Flat Roof systems will have a life expectancy in excess of 30 years

• Cracks in membrane. Surface cracking may be okay but cracks of more than 2-3mm deep indicate membrane is nearing the end of it’s life.

• Material has become brittle over time. It will not tolerate structural movement.

• Laps will become loose allowing water ingress

• Roofs with a stone chipped finish will generally be over 25 years old

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Incorrect Detailing

• Poorly applied membranes

• Bad terminations into abutments.

• Badly cut chases – Should be generally 25mm deep

• Use of incompatible materials and proper sealants

Identification of Defects

• Identify frequency of water ingress. Is it under a wind assisted rain, heavy rain or possibly when it is not raining!

• Look for signs of repair or different materials used to patch

• Check for tide marks indicating poor drainage –possible blocked pipes or rainwater outlets

• If in doubt call a reputable contractor.

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Flat Roofs – Fire Prevention

• Fire risks• Safe2Torch• Best practice and use of safer

torching techniques

Typical details with Fire Risk• Abutting slate details with historic dry timbers

and dust• Abutting cladding details

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Safe2Torch is an NFRC campaign developed in partnership with contractor and manufacturer members of the NFRC, seeks to significantly reduce the risk of roof fires when using gas torches, either to dry out roofs or when used to install torch-on membranes.

The campaign promotes the positive side of the industry, where safe specifications and safe working practices are second nature. It will give clients assurance that if they engage with a Safe2Torch Contractor and/or Manufacturer, their roof works will have been planned and installed within the requirements of the Safe2Torch guidance

Fire Prevention –Best Practice

• Avoiding use of heat almost impossible in bonded waterproofing systems.

• Reduce the use of heat at project design stage.

• Self-adhesive & Thermally activated Membranes should be used as part of the waterproofing system when fire is a risk.

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LATEST DEVELOPMENT OF BITUMEN ROOFING SYSTEMS

• Eco-Activ® membranes are coated with Noxite®

mineral granules, incorporating Titanium Dioxide (TiO2).

• Titanium Dioxide is a photo-catalyst and in the presence of sunlight breaks down NOx into harmless levels of nitrates.

• The nitrates are then washed from the surface of the membrane during rainfall events.

• The concentration level of nitrates are less than those found in bottled mineral water.

NOx pollution passing over the membrane. TiO2 releases energy in the presence of sunlight to convert the NOx

NOx converted into nitrates Nitrates washed away by rainfall. Levels less than those found in bottled mineral water

Latest Development of Bitumen Roofing Systems

The mineral surface of the bituminous Noxite waterproofing membrane has a titanium dioxide (TiO2) coating which acts as a catalyst in the process of converting NOx gases into harmless levels of nitrates

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Warranties

• Most Modern Flat Roof Systems will offer Insurance Backed warranties for Material AND Labour through trained installers

• Insurance Backed warranties can be purchased via the NFRC Co-Partnership Scheme

Slate Roofing & Defects[Steve Scott]

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Agenda

• Introduction• Slate selection and specification• Inspecting slate roofs• Common defects• Repair or renewal• Summary• Q & A

►Often an undervalued craft

►One of our traditional trade skills

►Requires a four year apprenticeship to reach advanced craft level

►Training split between the work place and college

►Wide range of skills required to be a successful tradesperson

►Works with a wide range of materials

►Worldwide opportunities for employment

Roof Slater & Tiler

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Slate Selection & Specification

►BS 5534

►BS 8000 Part 6

►NHBC Standards

►NFRC Technical bulletins- Full list on www.nfrc.co.uk available for free download

►BS 5250

►BS 8612

Slate Selection & Specification

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►Various considerations►Performance►Cost►Aesthetics►Planning constraints►Availability►Guarantees►Location►New or secondhand

Slate Selection & Specification

Slate Quality –Imported Slate

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►At its peak in 1898 Scottish slate quarries produced over 650,000 tonnes annually.

►Last Scottish quarry closed in 1960’s

►No Scottish quarries

►Now reliant on secondhand supplies

►Finite resource

►Alternatives?

Scottish Slate

►Good quality secondhand Scots

►Good quality secondhand westmoreland

►Good quality secondhand welsh

►New welsh

►New westmoreland

►New Spanish- Cupa H3

Common Slate Types

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Secondhand Westermoreland Re-slate

New Spanish (Cupa H3) Slate

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Secondhand Scots Re-slate

►Safe access

►Use of drones/ cameras

►What to anticipate: materials/ fixings or detailing

►Defects not always immediately apparent

Inspecting Slate Roofs

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►Failure of fixings►Slipped/ damaged slates►Incorrect headlap►Poor detailing ►Poor detailing, particularly at cuts into valleys or skews►Over reliance on mortar at detailing►Poorly installed, selected or failed underlay►Poor repairs by non qualified person►There are of course many other defects!

Slate Roofs – Common Defects

Tile Roof Defects

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Mortar Failures -Verges

Slate Roof Defects

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Slate Roof Defects

Slate Roof Defects

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Slate Roof Defects

Slate Roof Defects

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Slate Roof Defects

Repair Work in Action

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Heritage for future generations

Renewal

Heritage for future generations

Renewal

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Effective repair or renewal not

Safe working

Effective repair or renewal not

Unsafe working

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Any Questions?

www.nfrc.co.uk@TheNFRC