Adverse weather conditions (wind, rain, frost and snow) can have a drastic effect on buildings and the building process.
Wind
Britain is one of the most windy countries in Europe. The Building Regulations require buildings in Britain to be designed to withstand wind speeds ranging from 85 mph (37 metres/sec.) in the south to over 120mph (54 metres/sec.) in the far north of Scotland. Thankfully, winds of this strength only occur about once every 50 years. In any case, strong winds are a feature of the British climate, particularly during winter months.
Bear in mind that we are living during a period of climate change; therefore we may experience greater variability in weather conditions and more extreme weather conditions.
While the London Borough of Waltham Forest is not severely exposed, it is not immune from the effects of variable weather. Tall buildings and those on hills are more exposed to the elements.
While weather forecasting (Meteorology) has improved considerably in past decades, it is still an inexact science as was shown graphically by the storm of 1987. The Meteorological Office issue severe weather warnings to warn of approaching storms and rainfall likely to cause flooding
Nevertheless, when a severe weather warning is issued reasonable precautions should be taken:
Secure loose objects such as ladders, light garden furniture or anything else that could be blown into windows or other glazing.
Close and securely fasten doors and windows, particularly on the windward side of buildings, especially large doors such as garage doors. If a building is fitted with storm shutters, ensure they are closed securely.
Close and secure loft hatches, particularly if the roof has a shallow pitch.
If chimney stacks are tall and in a poor condition, move beds from directly below them.
Park vehicles in a garage if there is one available, if not, park away from buildings, trees, walls and fences if possible.
This list is not exhaustive. Generally speaking, do not put yourself or others at risk.
During a storm
If you must go out, try not to walk close to or shelter close to buildings and trees.
Be particularly careful if a building is shedding roof tiles, slates or other materials. Keep away from the sheltered side of boundary walls and fences as if these structures fail, they will collapse on the sheltered side.
Do not go outside to repair damage while the storm is in progress.
If possible, enter and leave buildings through doors on the sheltered side, closing them behind you. Keep internal doors closed.
Roofing works, other than emergency repairs, should not be carried during periods of strong winds.
Do not handle or lay sheet materials in strong winds (force 5 or greater).
Do not lay bricks or blocks or render walls in strong winds (force 6 or more).
Walls that do not have adequate returns or other means of restraint may need to be propped if strong winds are forecast.
Newly constructed walls should be inspected for damage if strong winds occur soon after being built.
Frost and snow
If ambient temperatures are low enough to delay the initial setting, concrete will not develop its full strength. Concrete should not be mixed or placed if the air temperature is not at least 3 degrees Celsius (C). The minimum temperature for placing concrete is 4 degrees C (steady) or 3 degrees C (and rising). These temperatures should be sustained or exceeded for the concrete to start to set properly.
Frost bound aggregates should not be used.
Local conditions may increase the risk of low temperatures. Temperatures decrease by about 0.6 degrees C for every 100 metres above sea level.
An unprotected concrete slab should not be laid during heavy rain or snow showers.
Bricks or blocks should not be laid, nor render applied, in temperatures of below 2 degrees C or if the temperature is expected to drop below 2 degrees C.
Green brickwork and render should be protected from rain, snow and possible overnight frost.
Do not handle or lay sheet membranes when the temperature is low enough to reduce their workability. Check the manufacturers instructions for the minimum working temperature.
Wet or frozen surfaces are nor suitable for bonding to.
Do not lay a greater area of hot applied adhesives than will stay fluid while the membrane is laid.
Rain and flooding
Fortunately the London Borough of Waltham Forest is not prone to flooding.
However, overnight rainfall can made a mess of trench excavations. Water and any loose or soft material must be removed from trenches before concrete can be placed or drains laid.
If heavy rain falls on a freshly laid concrete slab, fine materials may be washed out, leaving the concrete, particularly the surface, weak and friable.
An unprotected slab should not be laid in more than the lightest of rain.
Bricklaying or rendering should not be carried out in the rain.
Render applied to saturated walls will almost certainly become detached. Rain will weaken mortar and stain face work.
Building materials, other than the most durable, must be adequately protected from the elements on site.
This information was correct at the time of writing (February 2007).
Contact us
Building Control
Environment and Regeneration
Waltham Forest Council
Sycamore House
Forest Road
London E17 4JF
Tel 020 8496 3000
Email building.control@walthamforest.gov.uk
Click here to return to Building Control home page
