Double Dormer Roof Extension

Dormer loft bedroom/office

The owners of this 1930's three-bedroom semi-detached house needed a dedicated home office to free up space. The light and spacious bedroom/office we created exceeded their expectations in terms of size and comfort.

Building control services were supplied by Approved Inspectors Ltd who checked that hight allowances, structural and insulation standards were in accordance with Building regulations.

Two roof dormers were added, one for the stairwell, the other for the bedroom. These create a roomy, comfortable loft area and a light and open up landing area.

Loft Plans and Permissions

The client approached us having already had architectural plans drawn up. Planning permission wasn't required because the design was within permissible limits, i.e. the dormers do not face the road, the additional roof area is within volume limits and the roofline is maintained.

Changes in 2008 to Planning legislation allow more roof dormers to be added without planning permission and the rules are designed for the layperson to understand. See the Planning Portal Animation (link opens new tab/window)

Side and rear dormers

We modified the initial plans based on structural calculations. The new steel joist under the roofline required the support of an internal wall. The changes showed building up an internal supporting wall to take the weight of the dormer frame.

The Building Control Officer used the plans to follow the construction plan, the materials and structural calculations.

Maximising Internal Height

Many clients stress the importance of maximising the internal head height in their loft. The roof pitch of this house meant the available height was just sufficient and we needed to employ 'tricks-of-the-trade' to ensure a comfortable internal height. Our plan and design experience helped us modify the existing drawings to ensure the internal height would exceed initial expectations.

Shape of the dormer

By thinking through the flat roof structure, we gained an additional six inches in height.

The client is delighted with the result; the ceiling feels high, and the room is comfortable and spacious enough for any use.

The space-creating method is to strap the ceiling joists to the top of the Reinforced Steel Joist. This places flat roof structure at roofline, at the permissible limit; our understanding of roof systems and materials allows us to modify the ridge tiles so they form a small lap rather than adding height when fixed along the ridge.

The flat roof has a vapour permiable layer and a green mineral felt torched on. During installation we ensured the felt actually laps over the flat roof edge and ridge line onto the top slates. The ridge tiles are sawn in-half lengthways and each rests against the ridge rather than sit atop it. They are mechanically fixed to keep them securely in position. The finished roofline appears identical to the adjoining roof and the shallow flat roof pitch channels rainwater as required.

The potentially wasted ridge tile height has thus been transferred inside.

Kite wind loft staircase

This professional, innovative solution is one of may we employ to ensure dormers look great and have maximum internal space. The final outcome surprised and delighted the client.

Dormer Bedroom / Office

The spacious loft room creates a fabulous office that can be easily transformed to a double bedroom if required. The view from the large window is over gardens and the surrounding countryside. Being elevated, horizon is relatively low and this allows more light to stream in throughout the day. The broad floor area and high ceiling provide ample head height and make the loft a pleasure to work in.

Lighting

Natural light floods in throughout the day from multiple sources. The east facing dormer window (three window panes) catches the morning sun, a stairwell window faces south to illuminate the stairwell and sunlight shines through an open loft door. A west facing Velux skylight allows in sun from early afternoon.

For nighttime lighting, we installed dimmable down lighters in three independent sets. These provide sufficient subtle light to create any mood. Down lighters on the sloping roof section will swivel to allow light to target strait down.

Rear dormer

Electric power

Modern living requires multiple power sockets so gadgets don't trail wires and can be placed easily whare needed. A multitude of electric, peripheral, lighting and internet cables can be run on independent power anywhere in the loft. Seven double electric sockets fixed low in the walls ensures convenience and safety. Additionally at eye level, we installed a double power and aerial socket for a wall mounted TV.

Heating and Ventilation

The modern central heating radiator on the supporting wall connects to the existing system and a fuel-efficient gas-fired combi-boiler. The heating system has ample capacity to serve the additional requirement even on the coldest days.

Ventilation helps keep the air clean, particularly if warm, sometimes moist air rises from below. Two dormer windows have latches and the Velux has a vent and can tilt open. There is also the vertical window installed with opener in the gable end staircase dormer. The loft can always feel light and airy, and in summer by opening opposite windows a summer breeze can pass through the room while the thick insulation keeps excess heat out.

House before conversion

Storage Space

Behind the insulated knee-wall is a large storage area. An access door is positioned midway along the wall for convenient access.

Side Dormer Stairwell

The side (gable-end) dormer houses a spacious stairwell and a solid flight of stairs leading up to the loft room. By placing the stairs in a separate dormer rather than positioning a staircase between two bedrooms we left existing bedrooms untouched. The deep stairwell lends a light and airy feel to the landing area, benefiting the rest of the house.

Loft Stairs

The space-saving double kite-wind staircase was designed and installed to fit over the existing stairs. Detailed measurements and calculation kept stair head height to an adequate height.

To maintain natural light and space into the original stairs we maintained an open structure to the finish (the steps of the two kite-wind turns are carefully plastered). This adds character, head height and space compared to a straight boarding option.

Fire Regulations

Fire regulations require lofts be a protected environment. Insulation in floors and walls is for thermal performance and fire containment. A fire door and fire resistant frame is required for the loft door. Other doors throughout the house also needed to be fire doors and we fitted these within the existing frames. The client selected the doors and handles to match internal decor. The new doors feel strong and have superior acoustic insulation too.

Roofing

Refurbished Slate Roof

The original roof fell short of current Building Standards. These require a waterproof, breathable membrane between the slats that hold slates and the roof joists. The membrane protects the roof structure and acts as a barrier should there be any damage to slates resulting in water ingress.

A new lead collar has been installed on the chimneybreast (made on site) and chimney flashings fitted to ensure watertight junctions around the chimney. Accurate re-cutting of slates provide a close fit around the chimney, roof light opening, edges and ridges. The high quality refurbishment ensures a long, trouble-free life and a roof that looks tidy.

Slates were moved from sections of the roof where the dormer is installed to the gable end dormer roof. Slates thus match the original roof covering. These original, slates are cleaned and checked for defects. They should provide another 80 years of trouble free service.

The dormer cheeks have a vertical slate covering too. The smaller slates we used provide a watertight, durable covering in keeping with the original roof.

Felt Covered Flat Roof

The rear dormer has a flat roof. A marine ply top layer is fixed to tapered battons for the shallow pitch needed for drainage. An ICOPAL vapour permeable bituminous layer is torched on to this followed by an ICOPAL green mineral felt-capping layer.

Drip formers on the edges keep rainwater and away from the roof structure and gutters and down-pipe efficiently channel rain water away.

The flat roof is guarantee for 25 years.

Gable End Dormer Roof

This pitched roof uses the original slates from where the rear dormer is positioned. The entire roof was re-battened and slated at the same time.

Dormer Cheeks

It is important to use materials sympathetic to the original house and in keeping with the neighbourhood. We explored several options for the dormer cheek covering such as lead faced (which can look industrial), timber sided (out of keeping) and pebble dashed (not as hardy as desired).

The client chose to use slate on the dormer cheeks. These help protecting the 'kerb-appeal' of the house and the underlying structure is very durable. Extensively use of lead seals around corners, window frames, sills and points of transition ensure long life and minimal maintenance.

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0800 505 3414

Dormer Loft Conversions in Cheshire, Greater Manchester and Lancashire