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Rigid PIR Insulation boards above between and below rafters at pitch roof level

Application - Flat Roof Applications

Flat Roof Insulation

including above, above + between, between + below, and below joists

Flat roof insulation projects are less complicated than those of pitched roofs.

Insulating above and between the roof joists is probably the preferred solution, and this method is often used in new-build and in retro-fit.

Unlike pitched roofs, flat roofs commonly have a built-up bitumen mastic, or similar, weatherproof external cladding, that requires major maintenance or replacement on a regular basis.

To minimise ongoing flat roof maintenance work, when undertaking a complete refurbishment, consideration is often given to replacing the flat roof surface with one that is more suitable for heavy traffic.

Rigid insulation boards are now manufactured to address this need.


Flat Roof Insulation - Installation Locations

Flat roof rigid board with single-ply, partially bonded built-up felt, mastic asphalt and cold liquid applied waterproofing

Above Joist installations ...

are common when insulating above a steel or concrete deck, or on top of metal girders.

Above and Between Joists installations ...

is the most common installation practice in a 'new-build' or re-roofing situations

Between Joists only installations ...

may be required where insulation above the roof joist level is impractical due an existing roof being in place, and insulation below the joist level encroaches upon the available headroom.

Between and Below Joists ...

where deep joists are in place this retrofit method is popular, particularly in Garage Conversions where the exiting joists are 140mm or more.

Below Joists only ...

where there is reluctance to remove existing ceiling boards, the application of mechanically fixed insulated plasterboard may be the only option



Flat Roof Examples - the Build-up, Insulation types and Combinations

New Build / Roof Replacement

Retro-fit / Loft Conversion

Built-up roofing of Bitumen Mastic or other Weatherproof external cladding

WBP Plywood or Insulation Plywood Laminate

Joist Cavity - Rigid Boards or Semi Rigid Slabs

Plasterboard or Thermal Laminate





Built-up roofing of Bitumen Mastic or other Weatherproof external cladding

WBP Plywood

Rigid insulation

1000guage Polythene VCL

Plywood

Joist cavity - optional Rigid Boards or Semi Rigid Slabs

Plasterboard or Thermal Laminate

Built-up roofing of Bitumen Mastic or other Weatherproof external cladding
Rigid insulation

Plywood

Joist cavity

Plasterboard

Built-up roofing of Bitumen Mastic or other Weatherproof external cladding
WBP Plywood or Insulation Plywood Laminate
Rigid insulation
Concrete deck


Built-up roofing of Bitumen Mastic or other Weatherproof external cladding
Rigid insulation

Plywood

Joist cavity

Plasterboard

Built-up roofing of Bitumen Mastic or other Weatherproof external cladding
WBP Plywood or Insulation Plywood Laminate
Rigid insulation
Concrete deck


Built-up roofing of Bitumen Mastic or other Weatherproof external cladding
WBP Plywood or Insulation Plywood Laminate
Rigid insulation
Steel deck

Soffit
Rigid insulation
Spacer batten
Cement board


Insulation for flat roofs waterproofed with partially bonded torch applied multi–layer bituminous waterproofing. Including between and over flat roof Joists, plus balconies and terraces

The brief examples above are indicative of the complexity of a flat roof build-up including insulation.

Generally foil insulation is not recommended for flat roofs due to potential condensation issues. However multi-foil insulation can be used in a warm flat-roof application. Care must be taken to follow the manufacturer’s instructions.

Consideration needs to be given to the amount of space available above and / or below the joists, as well as between the joists to locate the insulation.







Rafter Level Insulation Products

Rigid Insulation Boards

Semi Rigid Insulation

Multi-foil & Breather Foils

Breather & Foil Membranes

Plasterboards & Thermal Laminates

Celotex TB4000

Knauf Rafter Roll

YBS SuperQuilt

Tyvek Supro / Supro Plus

Celotex PL4000

Celotex GA4000

Knauf Earthwool Slabs


Tyvek Metal ProClad

Gyproc Plasterboard

Celotex XR4000

Rockwool ProRox Slabs


Tyvek Enercor

Gyproc Thermaline

Celotex FR5000

Rockwool Flexi Slabs



Kingspan K18

Celotex TA4000




Knauf Plasterboard

Kingspan TR24




Knauf Thermal Laminate

Kingspan TR26




Siniat GTEC Plasterboards

Kingspan TR27





Kingspan TR31











Our Contact Details

www.just-insulation.com

27 Massetts Road, Horley, Surrey, RH6 7DQ

Telephone: 0333 9000 989

Facsimile: 0333 7000 797

Email: enquiries@just-insulation.com

Web presence: just-insulation.com

Web Sites

just-insulation.com

Minimum order £175.00 ex-VAT. Delivery vehicle sizes - flexible

insulation-online.com

Minimum order £500.00 ex-VAT. Delivery vehicles size - 28 tons+

just-rooflights.com

Solatube natural light sun pipes. Courier delivery from manufacturer