How to Build the Perfect Pitched Roof

Building the roof of a house or replacing an existing one can be as simple or as complicated as you choose.  If you are replacing a roof, then you can go with what you had before to have the simplest choice but the question should be this; if you are replacing the roof, is it because something went wrong?  Might this happen again?  If so, then a change may be the best option in your quest for the perfect pitched roof.Pitched Roof

For a newly built property, considerations can be questions such as whether to tie in with surrounding properties or be different from others.  It may also be about the availability of certain materials and for both scenarios, unless you are really lucky, the cost will be the major factor.

Roof materials and styles

Roofs generally comes in two styles, though a complex roof can use a combination of both.  These are the gable roof and the hip roof.  Both of these styles use the same construction elements and have a different shape and pitch to them.  The basic elements used in any roof are:

  • Wooden joists – these support the weight of the roof
  • Wooden battens – also called lath, these tend to be treated to protect them from moisture and are fixed to the joists with nails.
  • Breathable membrane or underlay – this is added to keep rain out during construction and to offer protection should any water get through the outer layer. It is laid over the joists and fixed in place with nails.  In properties that are over 50 years old, this membrane may be absent.
  • Tile – this is the top layer made from one of the materials mentioned below and is the front line against weather damage

Labeled line drawing of the structure of a roof

With pitched roofs, there are a range of different options for what to put on the roof that generally fall into four categories; clay tiles, concrete tiles, slate tiles and thatching.  Concrete is the most commonly used in houses today while thatch is the most traditional.  Within these categories can be a number of choices, including shape and colour of the tiles.

Different types of tiles have different methods of application to the roof.  Slate, for example, will have pre-drilled holes in each tile that a nail is inserted into to attach to the wooden lath.  Clay or concrete tiles generally have retaining nibs at the back of the tile that rest against the lath.

Special tiles

The area where the two sides of the roof meet is called the ridge and special tiles are needed for this spot.  These are called ridge tiles and they are rounded tiles that overlap on both sides to provide a watertight seal.  Some use mortar bedding, often on the inside of the tile, to fix them to the other tiles and create that waterproof seal.  The joins between each ridge tile is also sealed with mortar for the same reason.

Roofs also sometimes have valleys in them, areas where two sections of the roof join together.  There are different ways to deal with the area including valley tiles that allow continuation around corners; open valleys where a metal or GRP lining is used or a closed valley finished with a pre-formed GRP strip.  Both of the latter are designed to funnel water down their length and into the guttering.

The edge of the roof is called the verge and the tiles on the end are normally fixed to prevent wind and rain blowing up and underneath them.  Mortar is the most common choice for this job, though there are other options.

Flashing is still commonly used where there is an area of brickwork joining the roof, such as a chimney and there are two main types; exposed or concealed.  Exposed flashing is the most common method and uses sheet metal such as lead, copper, aluminium or steel.

Cold and warm

One area to consider is whether you want a cold or a warm roof.  This may sound a strange question but it is to do with insulation methods and how much you use the loft.  Most houses now have cold roofs – this is where the insulation is laid onto the floor of the loft straight above the ceiling of the rooms below.  This means that the loft will generally be the same temperature as outside because the heat doesn’t get through the insulation.  If you use your loft for storage, this is ideal.

The other option is a warm roof where the insulation is laid against the inside of the roof between the rafters.  This is the style of roof that is ideal when the loft is regularly being used as a room as it will maintain it nearer the same temperature as the rest of the house.

Condensation

Before finishing the decisions about your roof, one last important area is to be understood; condensation.  This is where water vapour comes into contact with cold surfaces and creates drops of water or patches of dampness.  It is normal for there to be condensation in the loft because the warm air created in the house moves upwards until it finds the cold surface of the roof and creates condensation.

However, it is always advisable to reduce the condensation as much as possible and the main way of doing this is to ventilate the roof.  This means once the warm air reaches the roof, it has an outlet and doesn’t settle to create condensation.  How much ventilation is needed can be dictated by building regulations and how this is achieved can be in a variety of ways.

One idea are ridge vents.  These are a ventilation strip along the ridgeline at the top of the roof, usually, a strip of decking cut out from both sides of the ridgeline to let air move through.  One of the most popular options when using concrete roofing tiles are vent tiles.  A universal variation, for example, will work with almost any roof tile and use an adaptor and flexible pipe system to achieve ventilation.

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