Tom Wallace - Building Technology - Design



An opportunity

Even a very modest project - a house extension or a loft conversion - is an opportunity to do something interesting and exciting as well as creating more space for your property. You can enhance the neighbourhood, by adding to the sense of place that the surrounding buildings and landscape provide. You can enhance your home or workplace by providing a more energy-efficient building, through good insulation, and an up-to-date heating system with perhaps its own energy supply. You can enhance your lifestyle by choosing a design that uses natural materials and respects the planet. In the 21st century, and in one of the richest nations on Earth, it seems absurd that we settle for housing and buildings that are often just bland and uninspiring. In the sections that follow, this page looks at some of the most common alterations that people wish to make to their properties, describes the issues involved and offers a guide to getting the best results for your project.



A porch at the front of a house will require Planning Consent, unless it is very small. (See Consents page.) To the side r rear of the property, it would usually be exempt, unless the house is within a Conservation Area or is a listed building. Porches would normally be exempt from requiring Building Warrant. Providing an additional door between the inside of the house and the outside air is something generally encouraged by building regulations and makes sense in ecological terms. It is important however to maintain a good standard of door between the porch and the main house.

It’s often a useful feature to have an area of fixed seating to the porch, to allow two or three people to sit down at once and put on or take off footwear.

A row of identical houses in a street can benefit greatly from the houses having porches added, introducing a bit of variation to a street scene that might otherwise be dull. Too much variety however can appear cluttered. The porch may look to repeat the same wall and roof finishes as the main house, so as to balance any excess of complexity and might also replicate window, door and roof details from the main house.

Porches do not need to be insulated, but if there is an intention to not have a door between the porch and the main house, then it is better that insulation is provided to the porch, as it is then part of the heated space of the property.

For building materials, I encourage the use of clay block external walls, which can be rendered to match the existing house. A timber clad wall can also be effective for porches. For the roof finish, ideally clay tiles (referred to as Rosemary tiles in Scotland) or second-hand Scottish slate. The small size of clay tiles and slate make these materials especially appropriate on smaller porch roofs.

Wood-burning stoves


Stoves are increasingly popular and provide almost the only method of obtaining heat in the event of a power cut. The jury is out as to the environmental impact of stoves. It depends partly on where the wood is sourced. Collecting your own wood is probably the best option. If you are buying logs then it is worth checking where these are sourced. Another option is to have a stove that burns wood pellets. Although more expensive than normal wood, pellets burn with great efficiency and very little ash. They are also a much cleaner fuel.

In terms of pollution, many stoves are now registered to be used in smoke control areas.

Stoves can be fitted to houses with existing chimneys with very little modification required as long as the chimney flue is reasonably clear. An alternative is to install a flue liner to the existing flue and provide a suitable fitting at the chimney head. The illustration on the right above shows a retrofitted chimney. Alternatively a new metal flue can be provided. The illustration on the left above shows this option. Note that regulations require minimum distances from a flue outlet to the roof covering and these often mean quite a high flue.

If fitting a stove within an extension or a new build, there is always the option of building new masonry chimney stack. This may be the best option in Conservation Areas.

Depending on the stove, flue and hearth, there may be an exemption from the need for a Building Warrant. Please refer to the relevant section on the Consents page.

Loft Conversions

A loft can often be converted into a Bedroom or other accommodation without the need for Planning Consent. The exemption to this may be when dormer windows are to be installed. If the property is a listed building or is in a Conservation Area, then any kind of external change - for instance, rooflights, would require Planning Consent. Most loft conversions need a Building Warrant. Depending on the what is done to the loft, there are numerous factors involved for obtaining Warrant, and I try to summarise these below.

Allowing for a fully compliant stair and the forming of at least one apartment at loft level:- If there is only one apartment at loft level, the clear width of the stair, between handrails, can be 600mm. (An En Suite can be added without changing this rule.) If there is to be more than one apartment, then the clear width of the stir must be at least 800mm between handrails.

Fire doors would be required if the resulting house now has three levels - at least to existing and new apartments at every level. The council may also ask for Bathrooms, WC’s and Stores to have fire doors.

Smoke detection will be required, at least to every Hallway on every level. If the new stair is accessed directly from an apartment at any level, then smoke detectors are likely to be required in every apartment, and possibly additional fire protection measures introduced.

If the property is semi-detached or terraced, then separating walls, that is, the walls between the loft and neighbouring properties, will need acoustic insulation and one hour fire protection. Thermal insulation may also be required here, unless the lofts o neighbouring properties have already been converted to rooms. The acoustic insulation however often doubles as thermal insulation, so this may not require too much additional depth of material. There would need to be a service void provided towards the inside of the separating walls, so that service runs do not compromise the fire protection of the wall. Brickwork to separating walls would require a ‘parge’ render.

Sound protection may be requested to the ceilings of apartments below the newly formed accommodation.

Fire protection may be requested to the ceilings of apartments below the newly formed accommodation.

The ceiling ties to the loft - that is, the new floor joists - may require strengthening in order to comply with domestic floor loading.

If the building already has two levels, the new stair would require a door at the foot of the stair or a protected lobby space at the head of the stair. Providing this would avoid the more onerous fire protection measures mentioned above.

Substantial thermal insulation will be needed to the roof as the loft will become part of the ‘heated envelope’ of the property. This in turn is likely to require the introduction of roof ventilation.

As an alternative to forming apartments in the loft, accommodation could be providing that is simply referred to as Storage. If this is done with a fully complaint staircase accessing the loft space, then the following points apply:-

Fire doors as described above would still be required.

Acoustic insulation and fire protection would still be required to separating walls, but possibly not thermal insulation.

Ceiling joists - that is, the new floor - would still require strengthening.

Only lighting can be provided to the new accommodation, no heating, or power. However, the council may permit one switched socket outlet.

A door to the foot of the new staircase would still be preferable, or a lobby space at the head of the stair.

The loft space need not receive any thermal insulation, but in this instance, a lobby would need to be formed as described above, which would provide a thermal break from the heated areas of the dwelling. If insulation were added in the loft, then roof ventilation would be required.

If a ladder access were provided, then none of the accommodation in the loft could be apartments, it must all be regarded as Storage. This again would mean only lighting could be provided, with no heating or power. There may still be a need for separating wall requirements as described above. Otherwise, rooflights would effectively be the only part of this work requiring consent. There would likely be no requirement for thermal insulation, but if insulation were added to the loft, then allowance should still be made for roof ventilation.

More follows....

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