BUILDING BRIEFING: 

Protecting against frost damage 

A series of briefings on property defects and remedial techniques that property managers will commonly encounter and oversee throughout their management role.

One of the recurring nightmares of landlords is to discover that pipes have frozen in an empty property, then burst as the weather warms, leaving water cascading though the property - sometimes for several days - until the problem is discovered.  Preventing freezing of water pipes is not difficult or expensive. The cost of repairing the damage caused from a burst water pipe is out of all proportion to the cost of installing protection. One Cambridgeshire landlord was called out to his flooded property and incurred over £40,000 of damage. The tenants had gone away for the Christmas holidays without taking any precautions to protect the property. The pipes had frozen and burst leaving the property flooded, ceilings collapsed and carpets ruined.

Prevention

All cold water fittings located within the building but outside the thermal envelope, or those outside the building should be protected against damage by freezing. Pipes and fittings installed in rooms that are adequately heated are not at risk. It is pipes above ground or in unheated or hidden parts of the house that are at risk. These are also the places to check when improving the insulation of water supply and distribution pipes in an existing installation. Any pipes or fittings that are exposed to freezing conditions should be adequately insulated.

Adequate heating is the simplest form of prevention. No amount of insulation on pipes inside a building will prevent them freezing, eventually, if the building is unheated. Insulation will only slow down the escape of heat from pipes. If a building remains unheated for sufficient time, insulated pipes are as prone to freezing as uninsulated ones.

This means that if a building is to be left unheated and unoccupied for 24 hours or more in very cold weather, then either sufficient background heating must be maintained to stop the pipes from freezing, or the water and heating systems must be shut off, and the system drained to prevent any damage.

The simplest solution is, of course, to keep the heating system in the building running, but turned down to a low setting to conserve energy. Many modern thermostatic radiator valves now have a low frost protection setting at the lower end of the scale for this purpose (generally marked with a star symbol '*' ).

Locations to check

If possible, avoid running pipes near ventilated eaves, but if it is unavoidable, thoroughly insulate the pip

Pipes and cisterns in roof spaces are also susceptible to frost damage. The loft space should ideally be insulated to modern standards (150mm of mineral fibre or equivalent) - this will have the effect of forming a thermal envelope around the internal living space of the building.

The cold cistern and all its pipework should also be properly insulated. The cistern should be insulated on the top and sides, and not below it. This ensures that the cistern and its pipework effectively remains within the thermal envelope, not outside it. Pipework in loft spaces should, wherever possible, be located below loft insulation - again within the thermal envelope.

Pipework in other exposed locations also poses risk of frost damage. This might include pipework in:

• garages
• spaces near ventilated eaves
• unheated underfloor spaces
• positions near a window, exterior door,airbrick, ventilator, or other place where there are cold draughts

Trace heating

If externally exposed pipework cannot be avoided, then one solution is to fit trace heating. This is a form of localised heating which uses small thermal pads which can be wrapped around pipes, powered by small low-powered heating elements controlled by a frost thermostat so that they only switch on when it is sufficiently cold. Where trace heating is installed, it should be applied before the insulation is fitted.

Anti-freeze

Anti-freeze additives can be added to central heating systems via the feed and expansion tank or injected directly into the system via a radiator to give protection to sub-zero temperatures (typically down to -22 degrees C at 40% concentration).

Rented Property

The two common situations of concern to landlords and their agents are:

• when the property is tenanted, but the tenants have left the property unoccupied - perhaps whilst away on holiday; or
• when the property is empty over the winter period, between tenancies.

Whilst the property is tenanted, it is primarily the tenant's responsibility to ensure that adequate precautions are taken to protect the property against frost damage whilst the tenant is away. 

"He must, if he is going away for the winter, turn off the water and empty the boiler....."

These were the words of Lord Denning when describing the tenant's responsibilities (Warren & Keen, 1954).

Exceptions

Care must, however, be taken as this ruling is not 'watertight', and the landlord, and his agent still hold a general duty of care as to the condition of the property. If damage does occur, despite taking reasonable precautions, and the tenant can point to a design or disrepair defect in the property (such as unlagged pipework - see previous page), then the landlord or his insurer should expect to pick up the tab.

Nor does Lord Denning's ruling absolve the agent or landlord from the responsibility to act with due care when a frozen pipe has been reported. In Stockley v Knowsley BC (1986), the tenant telephoned twice to report frozen pipes before they burst but had not been told to turn off the stopcock, nor where the stopcock was. When the pipe burst, flooding was so severe that the tenant had to leave the property for one night and thereafter part of the property was unusable for 10 months. In fact, damages were awarded against the landlord (in this case, the borough council) for negligence.

The Court of Appeal held that landlords owe a duty of care to any tenant and that once they were:

appraised of the fact that a pipe was frozen and were aware, or should have been aware, that when the pipe thawed it would be likely to burst and cause water to flow out into the property below, they were under a duty to do whatever was reasonable in the circumstances, having regard ... to their capacity to act and their ability to abate or deal with the hazard.

More Information:

Understanding Housing Defects by Duncan Marshall, Derek Worthing & Roger Heath, 2nd edition. Published by Estates Gazette Books.

Protecting pipes from freezing - Good Building Guide No.40. Published by the Building Research Establishment