Timber & Damp Reports

At a glance...

  • Objective and honest answers – no exaggeration of defects or repairs
  • Good local experience
  • Damp and timber reports highlight rising damp, condensation, beetle infestation dry/wet rot
  • Costings for any repairs needed
  • Format acceptable to mortgage lenders

Drain Reports Surveyors and valuers will often discover dampness in the properties they inspect. Indeed, the Building Research Establishment (BRE) have estimated that over two million houses in the UK suffer from ‘severe’ levels of dampness with another two million affected to a lesser extent. In most cases, introducing water to building materials with a sealed, or semi-sealed environment isn’t a happy mix and leads inevitably to degradation of materials and sometimes the development of very serious problems. So, protecting our buildings from the effects of dampness is an important part of maintaining them. However, there are many different sources of dampness in buildings. They have different causes and require very different remedies. In some cases, several sources combine to cause problems. Contractors who apply a ‘one size fits all’ approach to corrective treatments are to be avoided. What is needed is a contractor or surveyor who understand how dampness can arrive in buildings and can give an accurate diagnosis of the source of dampness before an appropriate repair can be recommended.

Some of the more common causes of dampness in property include:

Rising damp

Rising damp is the result of water rising through the walls by means of capillary action. Moisture may stem from the soil around the outside of walls or from moisture rising through the floor construction. As a result of the capillary ‘lift’ through the fine pores in brickwork and masonry, moisture reaches a maximum height up the wall of about 1 metre.

To counter this effect in walls, the path of water up walls is blocked by builders incorporating an impervious layer into the wall at low level. These ‘damp roof courses’ (dpc’s) have been made of various materials over the years including such things as slates, engineering bricks and bitumen felt. Deterioration of the dpc material leads to failure in the barrier and allows moisture to rise, and if the dpc is bridged, for example by external soil being placed against the wall above the dpc level, then the dpc is rendered ineffective.

 

damp

 

Hygroscopic salts

An additional problem is that the water absorbed into walls in this way contains dissolved salts in the form of nitrates, sulphates and chlorides. These are left on the wall surfaces as the water evaporates. The problem is that some of the salts attract moisture (what is known as hygroscopic). As a result, if the salts aren’t removed, they continue to attract moisture into the wall surface which remains damp, even though other repair works have been completed.

Some current thinking has questioned the extent of genuine rising dampness in property and before that is given as the ultimate cause, therefore, a good surveyor/damp specialist will eliminate other potential causes of moisture, such as condensation, water penetration or plumbing leaks.

Penetrating dampness

Penetrating dampness is where water gains access to the building through its external fabric (wall or roof) and it is not as simple as its name first implies.  For example, water can penetrate a solid wall due to a number of factors: the high porosity or degradation of the brickwork, for example, or failure in a protective render (perhaps due to cracks or poor application), or even due to the orientation of the wall (south westerly elevations often face the fiercest moisture-laden winds). Each possible cause needs to be assessed and eliminated before an effective repair programme can be specified.

Water will find any gap through which to travel and all surrounds to openings and junctions of the building fabric are potential areas of weakness in resisting moisture. Doors, window and often skylights are vulnerable and need to be sealed as do joints between chimneys and roof coverings which are protected by flashings and soakers.

Water needs to be safely discharged away from walls as it drops from high level and a failure to do so may lead to water penetrating the external walls. So, guttering and downpipes that are leaking are a potential problem and even small detailing such as ‘drips’ formed on the underside of window cills, door thresholds and the base of render need to function properly to ensure that water doesn’t run down the face of external walls.

Bridging of Cavity Walls

In cavity walls, water will penetrate if the cavity is improperly ‘bridged’ by mortar droppings resting on cavity ties or by rubble dropped into the base of the cavity during construction. Both are examples of routes for external rainwater to find a way to soak the internal leaf.

Condensation

Condensation is a very common source of dampness in buildings. The fact is that the air around us and in our homes holds moisture (water vapour). The amount it holds increases with higher temperatures and when the temperature is cooled and it has more water vapour than it can bear, moisture is dropped onto the surfaces that have cooled the air close to them in the form of condensation.  To add to the problem, however, our lifestyles tend to create extra water vapour which enters the atmosphere within our homes when we shower or wash clothes and at the same time, our desire to reduce heat loss means that we have sealed our houses which keeps water vapour trapped and makes condensation more likely. Condensation is more likely in areas where air flow is restricted such as behind furniture and it is common to discover mould growth in these places.
Condensation occurs, then, when a coincidence of contributory factors occurs at a critical level. Temperature is one factor (affected by heating and insulation); water vapour discharged into the air is another; and ventilation (management of moisture laden air, if you will) is another.

As we have said, identification of the correct cause of dampness is vital before any repairs are recommended and will need the input of an experienced and objective specialist.  Superficial diagnosis can lead to defects persisting or unnecessary repairs being carried out.

There are, however, some generic symptoms that give clues as to the type of dampness that is present in a property. These are some of the most common clues –

Type of dampnessEvidenced by
Rising damp: High moisture readings to external or internal walls
‘Tide mark’ type staining of wall decorations at up to 1 meter height
Salts (called hydroscopic salts) on the wall surface
Penetrating damp: Often isolated to an area of damage to the external fabric
Worse during or following rainfall
Internal damage to decorations and finishes
Localised mould growth , if dampness is persistent.
Condensation: Intermittent – occurs when temperatures are cool.

Most damp and timber reports will include the following sections:

  • a description of the property
  • its age and construction
  • comment on restrictions to the areas inspected
  • a description of apparent defects
  • comment on the results of internal tests, such as use of a protimeter
  • a plan showing affected areas of the property
  • recommendation of repairs, if necessary
  • costings for carrying out the repair work
  • details of the warranty or guarantee for the work carried out

damp window

Insurance cover is often offered and described with regard to future works.

Correct repairs can only be recommended when the source of dampness has been accurately understood and diagnosed. All potential sources of damp in the building need to be considered and the all the symptoms of damp within the property need to weighed up to come to a conclusion. In the past, some contractors have been perhaps too quick to recommend installation of a chemical damp proof course when in fact this should only be advised when appropriate to eliminate the problems.

Remember also that dampness can be a source of rot in timber. Wet rot requires replacement and localised repairs of affected areas, but if combined with restricted ventilation, conditions can exist which support the growth of dry rot. This is an exceptionally fast expanding problem and remedial costs can be excessive. Often, the root causes could have been prevented by quick attention to a damp problem.

The following summary shows some of the repairs commonly used to overcome damp problems. The list is not exhaustive and the particular circumstances posed by a property’s condition should always determine what repairs are advised

 

Type of dampnessCommon repair schemes
Rising damp: Removal of damp plaster and replacement
Overcome the effects of hygroscopic salts by replacing with plaster which has silicone-based waterproofing and fungicidal additives.
Allow wall to dry thoroughly
Renew affected joinery
Penetrating damp: Identify and remove any source of water to the external fabric (eg leaking gutter, defective render)
Repair/replace affected internal plaster
Allow wall/floor surfaces to dry thoroughly
Check for rot and repair nearby timbers as necessary
Make good to decorations
Condensation: Clean mould with weak bleach/water mix or proprietary products.
Restore the required levels of ventilation, heating, moisture content to affected areas.
Introduce management of moisture content such as mechanical ventilation to bathrooms and kitchens to avoid build up of moisture in the air.

Surveyors and valuers often recommend a timber report when they have identified either beetle attack within roof or floor timbers, or wet rot or dry rot (fungal infestation) somewhere in the structure.

The most common type of beetle infestation are shown below:

 

Type of beetleCharacteristics
Common furniture beetle Often called ‘woodworm’ and is a common feature of older properties.
Attacks sapwood typically, so in most cases, it doesn’t impede the structural function of timbers.
Flight holes are about 2mm diameter
Deathwatch and House Longhorn beetles Usually found in older properties
Attack hardwoods (such as Oak) and can cause serious structural problems over time.
More common in the South
Flight holes – Deathwatch approx 3mm; Longhorn up to 10mm.
Wood-boring Weevil Found in very damp timbers
Can be present in most wood types, but won’t survive if damp conditions are remedied.
Powderpost beetle Found in the sapwood of hardwoods.
Very destructive.
Fight holes up to 2mm

On of the main causes of deterioration of wood is wood rotting fungi of which there are two main types:

Dry rot  (serpula lacrymans)

Of these, dry rot is by far the more serious both because of its damaging effects on timber and its rapid spread under the right conditions.

Dry rot is identified by some or all of the following likely symptoms:

  • a cotton-wool like growth
  • vein like hyphae
  • drying and shrinking of timber into cuboidal cracking patterns
  • fleshy pancake type fruiting bodies
  • fruiting bodies can send out red dust spores

Wet rot (coniophora puteana)

Wet rot occurs in damper situations when the moisture content of the timber is around 30-40%. It occurs often in areas of consistently high dampness such as where joist ends bear into damp walls, window frames or jointing to external joinery.

Wet rot is identified by some or all of the following likely symptoms:

  • a series of delicate brown threads
  • shrinkage and cracking of the timber
  • darker colour to the affected area

Identifying a good damp proof contractor

Specialist Xpress work with specialists who are experts at resolving the problems of damp, rot and beetle attack in properties. Their treatments reflect the latest technology and their inspections are based on long established experience. All specialists apply thorough investigation techniques in order to understand the precise nature of the problem and to ensure that the repairs are entirely appropriate for the work required.

All contractors working with Specialist Xpress are members of the Property Care Association (which replaced the BWPDA). This is a body which maintains high standards of performance and knowledge from its members and is a way of confirming integrity and objectivity in reports. In addition, because Specialist Xpress have been working in this area for the last 17 years, they have the benefit of having seen which contractors deliver consistent results over a long period of time. This helps ensure that the consistently high service standards are achieved.

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