Much can be gleaned from an external inspection, but the full picture won’t be known without an excursion into the loft. Roof spaces are brimming with clues to the health of a building.

Even in modernised properties, the refurbishment work rarely extends as far as the loft, for the simple reason that most buyers tend to regard this as dead space. As well as providing pointers to a building’s age and construction type, investigating can also expose illicit structural alterations, pinpoint leaks and defects, and reveal the property’s thermal performance.

*All costs on these pages include labour and materials, but are provided as a rough guide only.

This piece includes:

Structural Defects and ‘Alterations’

Surveyors will be familiar with different types of roof structure, so alarm bells should ring if any bits are missing.

Common botched alterations include:

  • the misguided cutting away of supporting struts, collars or hangers to make more space
  • the removal of chimney breasts in bedrooms without providing proper support to the remaining masonry in the loft above
  • projecting bracing timbers are sometimes removed in a bid to improve headroom
  • in modern trussed rafter roofs (fink trusses) the W-shaped webbing may be hacked out to make way for illicit ‘loft conversions’

Not all structural defects are due to botching though. For example:

  • roof spread can occur where the rafters have pushed out the upper walls because they’re not restrained by ceiling joists — movement to the main walls below may be the root of the problem
  • persistent dampness can also result in localised timber decay

Common, less serious concerns include the lack of ‘lateral bracing’ – as found on early trussed roofs of the 1970s – which bolster the trusses against the risk of leaning, racking and buckling.

Anything with the potential to cause injury or collapse is going to be flagged up by your surveyor with a ‘red for danger’ condition rating. The cost of rectifying the problem will depend on the extent of the damage, but works such as providing localised strengthening to part of a structure needn’t be a major undertaking.

It’s important to bear in mind that without proof that Building Regulations consent was obtained for structural alterations (like loft conversions), your surveyor cannot be certain that the structure was adequately supported. This needs to be addressed when buying the house, otherwise it will simply resurface when you come to sell it on. Applying for retrospective consent is one solution, but this will involve a certain amount of opening up of the structure.

Remedial Work
Rectifying botched alterations will require a structural engineer’s report and a fresh Building Regulations application. In severe cases, partial rebuilding may be necessary. Unsupported chimney masonry will normally require the provision of a steel beam resting on load-bearing walls too.

With simpler defects, beefing up support with a few new timbers may be all that’s required. Upgrading the trussed rafter roofs with ‘lateral bracing’ simply requires fixing long timber battens horizontally and diagonally across the trussed roof rafters. This should be straightforward and inexpensive.

Pests, Nests and Vermin

Pests are not usually a serious concern, but they can cause short circuits or leaks (if plastic cables or pipes are chewed), and water tanks can become polluted. Eventually, they may spread to habitable rooms too.

The first signs are:

  • smells
  • droppings
  • straw/bedding material
  • damaged items
  • chewed cables and pipe lagging
  • small wasps’ nests are also particularly common in loft spaces

Remedial Work
Solutions include blocking up easy-access routes like gaps at the eaves, broken slates and open vents. Wire mesh can be fitted over large holes so that loft ventilation is maintained.

Traps can be used, or a pest control contractor hired. Smoke treatments effectively eradicate insects, and high-frequency sound devices are sometimes used to deter rodents.

The treatment of wasps’ nests can be done on a DIY basis if the right precautions are taken. Professional treatment will cost around £50* for making the nest inactive and £35 for removal.

Bats are legally protected, so specialist advice should be sought.

Missing Firebreak Walls

It’s not unusual in terraces to find that the original builders cut costs by omitting the party firebreak walls. This isn’t hard to spot — you can walk straight through to the neighbours’ lofts.

Even where party walls do exist, parts may be missing (often close to the underside of the roof covering), or they may only comprise of a thin, single skin of brickwork (a clue is where all the bricks are laid lengthways). The main worry with the latter is that it could be indicative of substandard walls in the rooms below, with subsequent noise implications.

This is potentially life-threatening, allowing fire to spread rapidly. It is also a security risk. There may also be poor support for the roof timbers. It’s easy to see why this is typically flagged up with a red condition rating in surveys. Ignoring this advice could lead to mortgage problems when selling the property on.

Bear in mind that the adjoining owner(s) will have legal rights over this wall and the Party Wall Act will apply, so specialist advice is required. On the plus side, the neighbour(s) may be willing to contribute to the cost. Building Control should be notified before work commences.

Remedial Work
A new firebreak wall will need to be constructed. Normally, a single skin of 100mm-thick Thermalite blockwork (about £65/m²) is adequate, or a studwork frame clad with two layers of fire-resistant plasterboard. Applying a skim plaster finish will help enhance fire resistance too.

Small gaps can be pointed up or stuffed with fire-resistant material such as mineral wool quilt. If noise transmission is a concern, party walls can be lined with acoustic plasterboard.

Damp and Condensation Build-Up

Dampness that isn’t caused by roof leaks is often the result of condensation. It can be due to driving rain penetrating thin gable end walls. Evaporation from the water tank and/or leaks from pipes may compound the problem.

Typical symptoms include damp loft insulation, roof timbers and ceilings. However, any sagging or torn underfelt is not usually an issue if the roof coverings are in a reasonable condition (replacing underfelt is uneconomic unless the roof is due to be stripped).

Poorly fitted extractor ducting serving bathrooms below can pump huge amounts of water vapour into the loft. Without decent loft ventilation to expel this humid air, it can turn back in to water, dripping on to the ceilings of the rooms below.

Damp shouldn’t be too difficult to rectify. Condensation is caused by warm, moist air filtering up into the loft and coming into contact with cold surfaces such as the roof tiles. The danger is that once surfaces become damp, they will be colder, more prone to condensation, and act as cold bridges that suck heat out of the building.

Once insulation gets wet, it becomes ineffective and loses the power to act as a thermal barrier. Sustained dampness in lofts can cause mould and rot to roof timbers, while decay to the wooden lathes which anchor the plaster in old ceilings can eventually loosen and drop off.

Remedial Work
To deal with condensation, you need to take a two-pronged strategy — limit the amount of moisture getting into the loft, and then provide sufficient ventilation so that any humid air that does make it through is wafted safely away. The sort of improvements which can make a difference, include:

Improving ventilation (see below)

Upgrading loft insulation over ceilings to at least a 270mm depth of mineral wool, taking care not to block ventilation points at the eaves. There’s a downside to improving the loft insulation though — the roof space becomes colder and potentially more prone to condensation. So maintaining a good through-flow of air is important to disperse any moist, humid air and prevent damp problems.

Filling holes in ceilings and insulating the loft hatch = £14 for a patch repair of up to 0.5m². If downlights in ceilings are boxed in above and the bulbs are changed to LEDs, insulation can be laid over them without the risk of overheating.

Checking all pipework and tanks for leaks, and ensuring a fitted lid is installed to the water tank if there’s not one already. Improving insulation to pipes and tanks within the loft space is also advisable to reduce the risk of pipes bursting. To insulate a 15mm pipe with 13mm of insulation = £10.50 per run.

Replacing the insulation jacket on a large cold water tank = £150.

Completely renewing defective extractor fans and ducting to roof = £156 (or more if external access is needed to the roof and scaffolding needs to be hired).> Cutting and replacing rotten roof timbers and those suffering active beetle infestation. To take out and renew a 50 x 125mm timber in a pitched roof = £90/m.

Thin gable end walls can be insulated and dry lined, with any eroded mortar externally repointed (or any defective render or tiles made good). To fix plasterboard to a gable end wall = £57 for the first m² and £29/m² thereafter.

Improving Ventilation

Most lofts rely on ventilation via the eaves, but these are commonly blocked by over-zealous stuffing of mineral wool quilt into the outermost reaches. In this case, insert purpose-made corrugated-plastic ‘vent trays’ between the lower rafters at the eaves to allow a clear air path without sacrificing the roof’s thermal performance.

If you don’t already have some form of vent fitted to your eaves, it’s a simple job to install new vents into the soffit boards (the underside of the box eaves):

Simple Method
Cut 70mm circular holes in the soffit at 250mm centres. Push-fit the plastic vents in. 

Continuous Soffit Vents Method
Continuous soffit vents (typically 0.05m x 2.4m) are installed by taking out the soffit board. Trim and refixed to the fascia with the vent strip in place. 

To boost the airflow, high-level tile vents can also be fitted. (Note that vented ridge tiles are not usually suitable for retrofitting.) Around three tile vents can be installed to each side of the roof to the upper courses. It’s likely to require a professional roofer, and for a total of six tile vents will cost around £350.

Although soffits are most commonly made of plywood, some are asbestos cement. It’s a light grey colour and very hard, and must not be cut due to the risk of inhaling fibres. In such cases, ventilating roof tiles are usually a better option.

In roofs with gable end walls, the simplest way to boost ventilation is by fitting air vents fairly high up at the opposite ends of the loft, with insect mesh applied to the inner face. This will cost around £250. Most of the above works will require scaffold hire = £200.

Ian RockAbout the Author

Chartered surveyor Ian Rock is director of the survey price comparison website and author of the Haynes Period Property Manual.

Image: John Lawrence

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