Carry out alterations on a listed building

Plymouth's topography means that views over rooftops are an important part of the character and appearance of many of our historic areas. The roof is often the dominant feature of a building and the retention of its original structure, shape, pitch, covering and ornament is important. Roofs are therefore an important part of the historic character of individual buildings and conservation areas. Choosing the right roof covering can be crucial in retaining the character of an individual property or area, particularly if part of a terrace.

Chimneys are also an important part of the roofscape. The use of unsympathetic modern replacement roof materials in different colours and textures can have a serious and detrimental effect on the character and appearance of an individual historic building or area, and are usually unacceptable.

Before re-covering a roof, it is essential to check its structural stability, and elements including chimney pots, parapet walls, gutters, valleys and rainwater goods. Special attention should be paid to detail when repairing a roof. Repair is preferable to replacement, which almost always leads to substantial loss of historic fabric.

Regular maintenance such as the replacement of individual slates, checking for nail fatigue, re-bedding of ridge tiles and cleaning of gutters and valleys is important to prevent future problems. If listed, listed building consent may be required for roof replacement. Check whether other consents are required such as building regulations and planning permission.

The main issue in repairing historic brick or stonework is usually the mortar used. Historic limebased mortars are softer than modern cementbased mortars and allow stone and brick walls to 'breathe' allowing moisture to evaporate naturally.

The use of modern cements in repointing or re-rendering historic brick or stonework doesn't allow moisture to escape in the same way, and will ultimately cause, or exacerbate, problems with damp. Using the right mortar mix is essential to ensure against ingress of water. Dirt, especially from traffic fumes, can also affect stone, as can be seen on many buildings in the city centre. Cleaning historic stonework requires specialist advice.

The key question to address is whether re-pointing is necessary. This will depend on the condition of the existing mortar and/or whether the right mix was used. Damp may be an indication of this, though it may be sensible to get an expert to assess whether the mortar has lost its integrity or whether the type of mortar used is suitable for the building.

The mortar mix should be softer and more porous than the stones or brick. Suitable mixes vary according to material and weather exposure. Analysis of historic mortar mixes may be necessary to identify any additives that may have been used to aid setting. In deciding on the mix, creating the right colour, texture and composition will be important. Joints must never stand proud of the wall face.

For listed building applications which include areas of re-pointing, either new build or repairs to existing walls, the mortar mix and a sample of the re-pointing may be requested through planning permission/listed building consent condition.

As with re-pointing, the key question should always be whether re-rendering is necessary. This will depend on the condition of the render and/or whether the right render was used. If damp is apparent within the property, this may be an indication that the render is not performing its job properly.

Traditional renders in Plymouth were made of a mix of sand and lime. Today, cement is usually substituted for lime though this can often cause problems in historic properties, particularly with damp and moisture retention. Many old mixes can be reproduced and used to repair historic renders. Painting historic or restored finishes needs to be carefully considered. Limewash is the traditional material, but if this isn't appropriate, specialist advice should be sought.

The key question with windows is whether replacement is absolutely necessary, there are a number of factors that should be considered prior to deciding whether the windows are in need of replacement.

Signs of ageing in old components aren't necessarily symptoms of irreversible damage. Often simple repairs, made at relatively low cost, can extend the life of the window. Where draught proofing, thermal and noise insulation are needed, there are ways to retain the original window and reduce heat loss. Cost effective solutions, such as weather stripping and secondary glazing, if detailed correctly, shouldn't look out of place or ruin the appearance of the window. There are ironmongery fittings for windows that allow traditional sashes to swing inwards to make cleaning easier. All aspects of your home need routine maintenance, through careful choice, there are 'microporous' paints for timber windows, which have a long guarantee (if applied correctly) and may require less maintenance. Security will always be an issue, there are a number of security features available on the market that are relatively easy to attach to your window.

If your property is listed, listed building consent is needed for all works of demolition, alteration or extension including the removal and/or alteration of windows.

Permission isn't needed for works of routine maintenance for example repointing, re-rendering, re-puttying, painting in the same colour, replacing broken panes, or replacing windows if these are an exact copy of the existing windows, using the same materials, finishes and design.

If your property isn't listed, but you live in a flat/commercial property, planning permission is required to replace your windows with units that are different in material, design or opening fashion from the building's original windows.

At present you don't need permission to replace windows if you live in an unlisted house (that is, not flats) in a conservation area, but please bear in mind that the area is designated because of its unique qualities and to protect it for future generations, the alteration of a single house in a group can diminish the worth of the whole.

In Victorian or earlier houses it is usually better to use exactly the same style of original windows. Many manufacturers of replacement windows fail to replicate the appearance and design of original windows, and these issues should be taken into account. For example:

Diagram A: This unit is unable to copy traditional designs. The arch on the right hand window of this pair has been lost in the left unit and been blocked in.

Diagram B: The glazed area of the opening casement (on the left) is substantially smaller than the fixed casement and bulky in appearance.

Diagram C: Modern replacement plastic window with a top opening vent relies on box sections for its strength and this leads to thicker profiles to the frames of the window, which are heavy in appearance and reduce the size of the glazed areas.

Diagram D: Top hung replacement windows unit set flush with the wall, the glazing bars are set behind the glass and the opening which produces an ugly angle from the face of the building.

Diagram E: The above contrasts substantially with this traditional timber sliding sash window, set back from the face of the wall.