Extensions & Loft Conversions.

05

Extensions

Many extensions may be simply specified according to the standard requirements of the Building Regulations, but in most cases the requirements of the site or the occupants demand bespoke designs to meet their needs.

This type of project may be our "bread and butter", but in each case we take great care to attend to the necessary details.

issues that commonly arise:

foundations

These need to be designed to take into account existing structures, nearby trees, drains, site boundaries and changes in ground conditions.

Party Wall Engineering

Excavation and construction near to site boundaries come into the scope of the Party Wall Act. Please refer to our section on Party Walls.

Roof Structures

The constraints of the site or maybe aesthetic reasons may require a special roof structure to be designed, especially at the junction with the original building. Roof windows, hips and valleys, vaulted ceilings – all must be considered. 

Open Plan Living

Large openings or the removal of internal walls reduce the inherent stability of a building, and in many cases extensive hidden structures are needed. Careful thought must be applied at the earliest stages of the project in order to realise the aspirations of the design at an affordable cost.

loft conversions

Some things to know about loft conversions

Loft conversions are increasingly popular as a means of maximizing the habitable space in your home. The Building Regulations ensure that the creaky old conversions of the past are no longer satisfactory.

The design of loft conversions is a speciality of ours, and these will achieve the same standards of strength and serviceability as any other part of the house.

In structural terms, there are two main methods of supporting the loft conversion:-

  1. the new floor joists may also support the roof via stud walls, and bear on the external and internal supporting walls, or
  2. steel beams are used to suspend the new floor joists and also support the roof.

Dormers can provide additional space or headroom, but these can enhance or disfigure the appearance of the building. Large dormers often require the introduction of a steel ridge beam to support the upper part of the roof. A change to the roof outline may require Planning Permission.

The need to remove the internal bracing in the roof structure usually requires the capacity of the rafters to be checked, and the roof structure should never be modified without expert advice. Features such as hips and valleys, chimneys and Party Walls will need to be addressed, and the geometry of the staircase is usually a critical item for the architect to consider.

Each loft conversion is unique, and even similar houses may have differing designs to suit the owners' requirements. Our designs are tailored to each situation, taking into account the original structure and optimising economy and ease of construction.

anatomy of a loft conversion

This example is based on a 19th Century end-terrace house, and has a “box dormer” on the rear of the roof. This requires a ridge beam to support the apex of the roof, as the rafters are no longer coupled as in the original roof. Parts of the structure are hidden to enable viewing.


Support Post

To avoid supporting the steel ridge beam in the chimney stack (which is often weak and sometimes poorly supported if a chimney breast has been removed), we install a steel post against the face of the chimney.

Support Post


Sometimes a steel beam is needed at the new floor level to support the post, if the load-bearing spine wall is not in line with the ridge of the roof.

In this case, the beam fulfils a second function to support the chimney stack, as the chimney breast has been removed below the new floor level. Often these are found to have been previously removed without installing any support to the 2 tonnes of old brickwork above!

Ashlering

To enable the collars to be removed from the loft space, the purlin supporting the front rafters needs to be supported. This is normally effected by a studwork “ashlering” wall taking the load down to the floor structure. Where headroom permits deeper joists to be employed, a steel beam is not always necessary as shown here.

Stairwell

To enable the collars to be removed from the loft space, the purlin supporting the front rafters needs to be supported. This is normally effected by a studwork “ashlering” wall taking the load down to the floor structure. Where headroom permits deeper joists to be employed, a steel beam is not always necessary as shown here.

Floor Hangers

The floor joists are mounted in steel joist hangers from a timber plate bolted to the top of the beam. They are restrained in place by timber packers between the joists (not shown).

Windows

The dormer structure is framed out in studwork, with timber lintels for the windows supported on “cripple” studs. The sheathing is not shown, but is vital for stabilising the framework. OSB or plywood panels are nailed to the studs and noggins (short pieces of timber) are placed to support the edges of the sheets. The sheet ends should be staggered to improve racking resistance.

Ridge Beams

The detailing of the dormer roof is often critical, as headroom is usually limited. There are a number of different ridge beam details that can be adopted to make the most of the available space.