Monthly Archives: January 2017

Roofing Materials

4 Types of Structural Roof Deck

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Timber Roof Deck Image Copyright: krakatuk / 123RF Stock Photo

Just as the overall foundations of a building are crucial to its performance, so the design and choice of material for a structural roof deck has a huge influence on the overall strength and performance of your entire roof.

In many ways, the roof deck is the backbone of any roof and requires professional design and top grade material. Although the roof deck is obviously important in terms of load bearing capabilities, it also influences everything from the roof’s thermal properties, waterproofing and performance when subjected to high winds.

4 Common Structural Roof Deck Materials

Roof deck can be constructed from many different types of material but the four most common are metal, concrete, wood and PIR (together with combinations of the above such as cementitious wood and reinforced concrete).

Metal
Metal roof deck is made from either steel (galvanised or coated) or aluminium. The metal is profiled, usually in a trapezoidal pattern, with its thickness, spacing, acoustic perforation and finish chosen to fit the span and load capabilities of the roof it is supporting.

Aluminium deck has a minimum thickness of 0.9mm while steel can afford to be slightly thinner at 0.7mm. Neither metal generally exceeds 1.2mm in thickness.

The exact type of metal deck required will depend upon many factors such as the amount and distribution of load (which will effect midspan deflection and hence drainage performance), aesthetics and how the deck is to be integrated with the roof’s insulation and waterproofing systems. This will also affect the type of fasteners you need.

Concrete

Concrete roof deck can either be pre-cast offsite and lifted into place with cranes (the quickest option) or poured while on site. Reinforced concrete (cast in situ) combines the properties of concrete and steel by setting steel bars within the concrete matrix, supplementing the compression strength of the concrete with the tensile strength of the steel. Pre-stressing the steel before the concrete is poured helps to increase the composite’s strength after curing (which takes around a month).

Made from a mixture of cement, fine aggregates and an expansion agent, autoclaved aerated concrete (AAC) provides a lightweight, flexible and workable material with the strength and fire resistance of concrete but at around a quarter of the weight. It is also water, insect and mould-resistant and provides excellent soundproofing but though tough is not quite as durable as concrete. In addition, building codes can make some uses of AAC impractical. AAC panels are joined to one another with a thinset mortar.

Wood

The vast bulk of wooden roof deck is supplied as pre-formed sheets although timber boarding is used during re-roofing work.

New timber roof deck is normally at least 25mm thick and connected using tongue-and-groove joints to protect from shrinkage. Alternatives to real wood include OSB – a material formed of bonded cross-directional timber strands – and plywood; these materials are normally no less than 18mm thick.

When using these options for a roofing project it is important to be aware of the relevant BS standards that are required (e.g. EN300 for OSB and EN636 for plywood).

Cementitious wood fibre deck combines the properties of timber and cement including workability, ease of installation and acoustic control.

Polyisocyanurate (composite)

PIR is a modern plastic foam which has superb insulating properties. In roof deck, it is often bonded with a steel liner to create a waterproof and thermally efficient layer.

This is just a brief introduction to the four most common types of roof deck you are likely to come across. Your roofing supply merchant will have more specific details about the best type of deck for your specific project.

Conservatory Projects, Conservatory Roof Conversions, Conservatory Roofing

Room Conversion Options: Conservatory Upgrades

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Conservatory room conversion image copyright: davidmartyn / 123RF Stock Photo

When homeowners start looking at ways to increase living space or add value to their homes, they often think about room conversion as a more affordable alternative to extending their property. Loft conversion is one of the most popular projects while garage conversions are also high up on the list.

However, if you have a conservatory attached to your property it is possible that you can enjoy all the advantages of room conversion at a fraction of the cost of the previously mentioned options.

Why Conservatories Make an Ideal Room Conversion Project

As detailed further below, changes in planning laws combined with a revolution in materials and construction technology have taken away a lot of the hassle out of conservatory conversions. Homeowners no longer have to put up with the cost and disruption of a full conservatory-to-sunroom extension project and can simply replace their old polycarbonate or glass roof with an attractive lightweight solid alternative.

Solid tiled roofs are very popular today for a number of reasons:

  • They are relatively affordable.
  • They are quick and easy to install.
  • They contain their own insulation, making your conservatory habitable in the winter.
  • They reduce the noise of rain on the conservatory roof.
  • They vastly reduce the amount of glare from the sun – better for many tropical plants, furnishings and electrical equipment.
  • They reduce the ‘greenhouse effect,’ ensuring your conservatory doesn’t get too hot in the summer.

Building Regulations and Planning Permission

If you do opt for a conservatory conversion with a solid roof, you need to consider whether your alteration comes under the definition of ‘change of use,’ under Building Regulations. This advice from the LABC should help to clarify your situation.
Recent changes mean that you may not need to apply for planning permission for this type of room conversion. Here is some planning permission advice from Metrotile (and if you are interested in a Metrotile roof, contact Roofworx SW conservatory roof conversions).

So, before you jump on the loft conversion bandwagon, consider how improving the utility of your conservatory might be a better room conversion project, saving you money that can be used to kit out your newly habitable room into a year-round family space.

Roof Styles, Roofing Projects

5 Roof Styles: Benefits and Disadvantages

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Roof Styles Image Copyright: cuchina / 123RF Stock Photo

When designing a new house or adapting the style of an existing one it is worth spending some time deciding which of the many different roof styles would be best to construct. As people’s needs and tastes change and roofing materials and technology evolve there is more flexibility than ever. However, the impact of the elements is still a factor that needs to be carefully considered.

Here are five of the most commonly seen roof styles together with an idea of their pros and cons.

1. The Gable Roof

Simple to build, relatively cheap, spacious, well-ventilated and rain-resistant, the plain gable roof (pictured) is (and probably will always be) one of the most popular roof styles in temperate countries (although there is more experimentation in newer homes today). With only the one seam, a properly tiled side gable is perfect for shedding rain and, providing it is pitched at 40 degrees or more, snowfall too. Homeowners with gable roofs can opt for high vaulted ceilings or extra rooms to maximise their living space.

More complex gables such as crossed gables and dutch gables (a gable on a hipped roof) require extra attention to the types of tiles used and how those tiles are laid to ensure the valleys are properly waterproofed but they are still more water-resistant than many other roof styles.

If there is an Achilles’ heel with gable roofs then it is when you come to very windy areas. Open gables are particularly vulnerable to wind getting up under the roof and this can, in extreme cases, cause the whole thing to lift off. Gable roofs which are poorly constructed can also suffer from the direct impact of gales so it is always worth having your roof checked regularly if you live up on the cliffs or out on the moors.

2. The Hip Roof

The standard hip (or hipped) roof consists of four sides of equal height which slope up to meet at a ridge. The geometry of a hip roof makes it much more stable when it comes to resisting the wind while the pitched sides protect the house from rain and snow. Just like a gable roof, there is plenty of ventilation and scope for extensions further down the line.

The main disadvantages of a hip roof is an increased vulnerability to leakage due to the extra seams and the extra material and labour costs involved since you will be using more materials and the structure is more complicated. See our separate hip roof article for more details about the pros and cons of this type of roof.

3. Flat Roof

Until recently, flat roofs have been generally dismissed as a bad idea by homeowners unless they were planning to build a shed. Although flat roofs are generally pitched to a slight degree to allow water to run off, they are often unable to cope with serious wet weather and tend to spring leaks, requiring constant patching up.

But with new, more waterproof materials and designs coming on to the market, the flat roof has become more popular in modern homes, particularly in relatively dry and sunny parts of the country. Easy and inexpensive to build, a flat surface can be used to support everything from patios and penthouses to fully-fledged gardens.

4. The Lean-To

What could be easier and cheaper than a pitched gable roof? How about half a pitched roof? Also known as a skillion or mono-pitch roof, the lean-to is a flat roof with an exaggerated pitch to help with shedding water and snow. It is becoming more popular with modern homes but can mean putting up with low ceilings in some rooms. Just as with gable roofs, wind can also be a hazard.

5. The Mansard or French Roof

The Mansard roof is sometimes overlooked because of the initial build expense but this can be one of the most efficient roof styles of all. It is ideally suited to the homeowner who is expecting to extend the living space either for family or investment purposes. Few roof styles offer the flexibility and space of a Mansard roof with extra rooms (garrets) and dormers relatively easy and cheap to add when required.

The Mansard roof consists of a double slope with the bottom slope much steeper than the top slope. The exaggerated pitch of the lower part lends itself to creative shaping and materials can be selected for their appearance or price rather than their protective properties. However, with a Mansard roof it is important not to forget the shallow portion at the top which is more vulnerable to rain and snow.

Other Roof Styles

There are, of course, many other roof styles to choose, both variations and combinations of the above (boxed gables, cross-hipped roofs, overlaid hips, etc.) and completely different styles (e.g. gambrels, butterfly roofs and domes). We will feature more about these in future articles.