External Judgments About The Overall Quality And Desirability Of A House Will In Part Be Related To The Type And Quality Of Roof Choices. Where The House Is Already Part Of An Established Road With Similar Houses Of A Style And Age, It Is Very Unlikely That The Roof Type Will Be In Any Way Different. On The Other Had Where The House Is A New Build There Will Be A Greater Ability To Create A More Distinctive Roof Design Assuming That It Remains Fit For Purpose.
Flat Roofing History
Whilst Pitched Roofs Remain Fairly Standard For Roofs Of Houses, Flat Roofs Often Appear As A Necessary Roof Type In Most Major Cities In The United Kingdom Such As London, Birmingham And Manchester In Which The Density Of Population Has Forced The High Concentration Of Buildings Converted To Flats. One Of The Principle Reasons For The Quantity Of Conversions Was The Conjunction Of Population Re-Concentration After The Dislocation Of World War Two, And Social Driven Housing Policy That Focused Upon Providing Affordable Accommodation For Families.
In This Post-War Environment The Relaxation Of Building And Planning Controls Controls Contributed Towards A Movement Away From The Previous High Level Of Design Uniformity And On To A Position Where Roofs Became More Diverse By Type And Anchored In Pure Functionality Rather Than Clinging To Tradition.
Built-Up Roofing
Historically The Most Prevalent Flat Roof Method Or System Has Been Built-Up Roofing. The Essential Elements Which Combine Together Include Timber Roof Decking, A Vapour Retarder, Insulation Of Various Types, A Roofing Membrane And Surfacing Material. On Nailable Decks, Where Oriented Strand Board (Osb), Plywood, And Structural Wood Fiber Is Used , A Base Felt Is First Applied To The Deck, Bridging Joints In Order To Accommodate Changes In The Deck Dimensions. Remaining Layers Over The Base Sheet Are Solidly Adhered With Bitumen.
Roofing Membrane
The Roofing Membrane Itself Comprises Of Two Principle Components Which Interact, That Is Felt And Bitumen.Whilst On One Hand The Petroleum Based Properties Of The Bitumen Give Profound Waterproofing And Adhesion, The Felt As A Material Provides Critical Strength. In Turn The Membrane Remains Under A Final Surfacing Layer. The Surfacing Layer May Come In Different Variations But Its Purpose Is To Protect The Underlying Membrane From The Elements.
Cap Sheet
Typically Either A Cap Sheet Where Gravel Is Embedded Within The Bitumen Or Some Alternative Hardened And Reflective Material Is Used.If The Membrane Is Not Well Anchored, Roof Splits May Occur And The Membrane May Become Distanced From Flashings And Curbs.
Applying Felt
With Respect To The Practical Application Of The Method There Are Several Steps In The Process That Must Be Rigorously Adhered To. In Particular The Bitumen Must Be Heated Sufficiently To Insure Fluidity. When Spreading, It Has To Be Uniformly Spread With A View Towards Avoiding Creating Any Skipped Areas And Completing The Job Of Embedding The Reinforcing The Felts In Position Whilst The Bitumen Remains Hot. When Planning And Making Preparation For The Work, The Timing Of Weather Conditions Likely During Its Completion Need To Be Carefully Considered So That Cold And Wet Does Not Produce Moisture Trapped Within The Layers Of The System, Which May Produce Pockets Or Blisters. Therefore Every Effort Should Be Made To Keep All Materials Dry At Every Stage Of The Process.