Posts Tagged ‘Chevron Bracing’

ARCHIVE ARTICLE EARLY 2009

TWO DIFFERING AREAS THAT ARE CLIMBING

THE ‘CONCERN” LADDER WITH INCREASING RAPIDITY

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Modern Roof Trusses (prefabricated timber roof frames):

Adapted from an article at this website – http://www.building.co.uk/

PROinspect comment that the status-quo surrounding your own home WHEN IT WAS DESIGNED AND BUILT does not now exist. Climate-change and other factors have impacted in a way that is only now becoming invasive. Does/did your roof design factor in current wind patterns and strengths, rainflow patterns/amounts, snow-loading, wind suction caused by new dwellings/trees now close to your home?

Building site storage conditions plus the degree of construction knowledge by (and supervision of) Installers are prime determinants of quality when considering roof condition and suitability.

Truss Manufacturers’ instructions must be strictly followed (and made available to site operatives). All bracing is to be fully installed and multiple truss connections completed as set out in manufacturers’ details.

All structural timbers should be stress graded and marked KD (kiln dry) or DRY. Timbers must be preservative treated in areas where House Longhorn Beetle is a problem (a problem that is “notifiable” to your Local Authority).

“Good Design” is codified and is demonstrated by finding “good detailing” such as the following:-

• Roof bracing should be twice nailed every truss.
• Diagonal bracing should be fixed at an angle of between 35° and 50° and fixed not only to the trusses but also to the wall plate. Overlaps should be carried over at least two trusses.
• Longitudinal bracing should be positioned tightly to abut separating and gable walls.
• Chevron bracing should be installed where the span of the roof exceeds 8 m.
• Seek confirmation from the roof designer that a trussed-rafter roof design can support water storage tanks. The use of bearer beams and supports fixed with moisture-resistant plywood or OSB sheet material used for the platform should form tanks stands. The tank bearers should be sited as close as possible to the node points and bear across a minimum of four trusses.
• Lateral restraint is needed on gable masonry. Lateral restraining straps and associated noggings must be fixed to roof truss rafters and ceiling cords at 2 m centres across three trusses. For cavity masonry, the straps should project and fit tightly on the outside face of the inner leaf of blockwork.

PROinspect have found that problems are often associated with condensation (often because of ill-advised “thermal” or “loft-conversion” improvements), DIY project “improvements” or where too much has been stored in the loft space.

Dry Rot and Wet Rot – a Surveyor nightmare?

Adapted from an article upon the website of the WOOD PROTECTION ASSOCIATION.

Dry rot and wet rot can affect buildings of all ages and if decay is discovered it should be identified and remedial action taken without delay. Such problems are often detected as soon as new home owners move-in because this is the first, and often the only, time when the home is empty of coverings, possessions and furniture. Often decay affects flooring that can spread behind plasterwork and other claddings, often undetected for many years.

An Owner “best defense” option is to annually inspect your home with a critical eye and to pro-actively maintain, paying close attention to the smaller details. The following notes may help you help yourself:-

Fungal decay occurs in timber that becomes wet for some time and is the result of the attack by one of a number of wood-destroying fungi. The most well known are Serpula lacrymans the True dry rot fungus; Coniophora puteana the Cellar fungus and Poria vaillantii the Pore or Mine fungus.

Many other fungi also occur and some have recently been particularly linked with decay in door and window frames.

Fungal decay always arises because the wood has become wet, about 20 per cent moisture content. This can be accelerated by limiting essential ventilation and creating dark/dank conditions.

Finding the source of dampness, eliminating the ingress of moisture and promoting drying is always necessary. However, the main problem facing those asked to investigate such matters is lack of adequate access to flooring – without clearly furniture and lifting fitted floor coverings Surveyors can easily miss signs of decay unless there is a strong trial of disturbance elsewhere such as springy flooring (when walked upon), wall dampness staining (disturbed plasterwork?), fruiting-bodies on closeby visible joinery etc…

Therefore the best defense potential buyers have is the service of an experienced Inspector. It is for this exact reason that PROinspect strongly advise buyers to separate Loan Valuations from Private Surveys to ensure YOU control what expertise is employed on your behalf.

Common Causes of Dampness in Buildings

The first step after discovering fungal decay is to make a careful inspection of the building to find how and where the water is entering. The defect permitting access of moisture must be treated and further entry prevented and the area dried out.

External Inspection – will an Inspector have free, uninterrupted access to all elements/areas?

The Roof

1. Blocked or misaligned gutters, especially in the hidden valleys of the roof.

2. Defective surfacing to valley gutters and flat roofs.

3. Missing, broken, displaced or loose tiles or slates.

4. Faulty flashings around chimneys and parapet walls.

The Walls

1. Excessive deterioration of mortar in brickwork joints.

2. Faulty or missing damp-proof course.

3. Bridging over the damp-proof course by soil in flower beds, plinths, etc.

4. Blocked air-bricks.

5. Cracked or broken pipes, both water-pipes and waste pipes.

6. Faulty flashing around window frames (inc. throats to cills).

7. Continued function of overflow from cisterns or water tanks.

Ivy or other climbing plants may hide many of the above faults and roots may undermine foundations causing breaks in damp-courses.  Roots of nearby trees may cause similar damage to foundations and damp-courses (and drains).

Internal Inspection – will an Inspector have free, uninterrupted access to all elements/areas?

Look for the evidence of moisture penetration where outside inspection has identified faults. In addition a number of potential causes of dampness will not be visible from the outside:

1. Solid stone or concrete floors with wooden skirtings and/or covered with timber where the         impervious membrane is punctured or of poor quality or where no membrane is fitted.

2. Condensation – this may be caused by:

a) unlagged steam pipes, especially under floors;

b) steam condensate, particularly in wet process factories;

c) high atmospheric moisture from normal bathroom and kitchen usage. This is especially important in uninsulated and/or poorly ventilated buildings and is the cause of much window joinery decay (sometimes self-inflicted because we do not open windows OR turn-off extractor-vent devices!).

3. Trapping of flood-water in under-floor space and over concrete.

4. Old toilets, either from fracture of the pan or, more commonly, from deterioration of old lead and sacking joints connecting the flushing water-pipe to the pan.

5. Close-fitting linoleum or vinyl flooring laid over unventilated or imperfectly ventilated wooden floors.

6. Ill-vented loft spaces (often due to over-insulating by Owners OR simply because of poor design).

Adequate sub-floor ventilation is vital and careful attention must be given to clearing blocked air vents (at the base of perimeter exterior walls) or air-holes in sleeper walls (brick support walls under mid-span of ground floor timbers). Dead air pockets in such unlit areas favours fungal decay and should be eliminated.

Steps must be taken to dry out existing dampness and to prevent further entry of water in addition to the eradication of the fungus and repair of damage caused. This is an invasive, damaging process that is both costly and a long process and one that is not normally covered by Building Insurances.

PROinspect comment that, especially with older or complex buildings, it is essential that clients talk to their chosen Surveyor: that person must assess what inspection problems he/she may be faced with and advise the client that perhaps specialist access equipment will be needed; seller permissions may also be required as limited damage may be created in this process.

By letting “others” instruct Surveyors on your behalf you are not getting the best for your money and this may cost you greatly when/if repairs are discerned at a later date.

Remember, always separate the Loan Valuation inspection/product from your private survey needs.