Condensation

When working with roofs, cladding or windows, it is important to take condensation into consideration.  When working with timber-framed buildings, it’s essential.  People generally believe that condensation can be cured by fitting double-glazing.  It can’t.  It just moves the problem somewhere else.
A short explanation. . .
Air usually contains moisture. The warmer the air, the more moisture it can hold.

Also, the higher you go, the cooler it gets. The bottom edge of the clouds is where the air is too cool to hold moisture without it condensing . . . into cloud.
It’s much the same in a house, except that water vapour is let out of the bathroom window before it forms into real clouds. The air in warm houses (and roof spaces etc.) can hold more moisture than cold ones. If any surface, such as a window, wall or roof, is cold, moisture will condense on it.

Fit double-glazing and the moisture goes somewhere else - usually the north-facing wall. Where the temperature falls below the air’s ability to hold moisture is called Dew Point. If it occurs within a wall (especially a timber-framed wall) this causes problems.

Damp proof membranes keep rainwater out but they don’t stop the build-up of condensation. “Dew Point” can be calculated and, ideally, it should always occur in the middle of the cavity of a wall. If it’s in the inner leaf, it leads to mould growth - the first (but not the last) sign of trouble.

Ventilation

Roofs divide into two main categories - pitched and flat. Most of them are made from timber, usually with the ends projecting beyond the walls to ensure they keep the rain out. After that, it starts to get more complicated because there are “warm” roofs and ”cold” roofs, and most of them, these days, require ventilation to prevent various forms of decay that might attack the structural timbers and metal components.

Ventilation is provided at the eaves by means of simple purpose-made Iouvred soffit boards but, to be effective, it must be at both sides of the roof and unobstructed. If it isn’t, the air can’t circulate because, if it’s to get in effectively, it must be able to get out somewhere else.

The louvred slots are small enough to prevent birds from getting into the void of the eaves, and insect mesh is also available.

Asbestos

Refurbishment work might involve soffits that were made from a range of asbestos-based boards. Chrysotile is a fairly common white asbestos board, whilst Amosite is made from brown asbestos, Crocidolite from blue asbestos - all extremely hazardous substances.

Before removing, replacing or working with any type of asbestos, it’s essential to know the risks and to guard against them. New legislation was introduced in February 1999: ACOP - the Approved Code of Practice, the control of asbestos at work and work with asbestos insulation, asbestos coating and insulating board (Third Edition) gives advice on how to comply with the law.

Safety - It’s always wise to check for the presence of asbestos and, where it’s believed to be present get it tested.
When working commercially, on jobs where the Construction (Design & Management) - better known as CDM - Regulations apply, you’ll need written method statements stating how you deal with these eventualities.

The Health & Safety Executive’s (HSE) advice is usually quite clear on the matter - if possible, leave asbestos where it is. This means over-boarding, no bad thing when asbestos-based boards aren’t liable to rot or decay. By leaving the asbestos where it is, you’re also doing your bit for the environment by avoiding the need to dispose of the stuff.

Where asbestos must be removed, it’s a specialised (and therefore expensive) job, requiring the right equipment, such as face masks and disposable overalls, the right precautions and strictly-controlled methods of disposal. Whenever asbestos is disturbed, tiny particles are released into the air. They are extremely hazardous to health. This waste must therefore be properly bagged but, even then, it can’t just be thrown into a skip because that isn’t the end of it. Sooner or later, it will surface on a waste site where it could become someone else’s health problem. Before messing with asbestos, the law quite rightly requires that you know what you’re doing . . . and can prove it.

 

Overboarding

Nothing saves money like covering up the existing surfaces. Time is saved because there’s no stripping off and therefore no waste to be disposed of. Before quoting for any job, be absolutely certain that overboarding is realistic. If in doubt, take a look at your Code of Practice.

The British Plastics Federation published the first Code of Practice for the installation of Cellular PVC-UE Roofline Products (Document Ref 350/1) in 1994, so everyone in the business should have a copy. For more information, and/or to obtain a copy, contact the BPF at 6 Bath Place, Rivington Street, London EC2A 3JE (tel: 0207 457 5000).
The Code offers best practice guidance on almost everything that’s encountered. In the event of a dispute between a dissatisfied customer and a contractor, this is the document that’s usually referred to. If you don’t comply with it, you’re more likely to be onto a loser.

One of the sections is advice AGAINST over-boarding. A case can always be made for doing it, especially where a couple have a reasonably new house (ten years old at the very most) and they’re only looking to reduce maintenance.

Anything older, and there’s always a chance that rotting timber (or worse) will be discovered. To put it another way, there’s the chance that it will be covered. A quote from the Code of Practice, to get your attention:
“To achieve a successful and safe installation, it is essential to create a sound, rigid, working substrate, It is recommended that total replacement rather than capping of existing timbers be adopted where possible.

By capping and effectively sealing moist, and perhaps already rotten timber, an environment which is more conducive to fungal attack will be set up and will result in a more rapid deterioration of existing timber. The capping board will tend to “insulate” the rot and promote conditions whereby the fungus can multiply and spread.”
In other words, if problems appear after overboarding, and the customer complains or, more likely, makes a claim against you, you’re going to be pretty much on your own.