Building/Construction works are usually outdoor works and these are mostly affected by bad weather. In countries located in the Southern and Northern hemispheres of the world, the coldest season of the year, called winter usually occur from December to February in the Northern hemisphere and from June to August in the Southern hemisphere. This weather is considered bad weather that affect construction activities. In countries located around the tropics, such as Nigeria, bad weather for construction activities is usually characterized by periods of heavy rainfall. Generally, typical characteristics of bad weather include: prolonged rain, frost, high winds, fog, snow and extreme sun etc.
When bad weather occurs, work output is affected, unemployment tends to rise because many workers are laid off or put on redundancy.
To circumvent the effect of bad weather requires, first, preparation for the bad weather and secondly planning for continuity of work.
Planning for Bad Weather
- Have a supply and issue protective clothing.
- Have portable heaters for drying and especially the interiors of buildings during frost.
- Build up stocks of sand or gravel to deal with icy conditions for transport to site, or entrance or exists.
- Hold a supply of tarpaulin, roofing felt, or plastic sheeting for protection of materials.
- Hold a supply of sawdust or shaving for floor protection especially during muddy condition
- Provide means of site lighting.
Planning for Continuity of Works
- Try to time the peak periods when fog, frost and snow are likely to affect construction activities.
- Prior to possibility of frost periods, concentrate of completion of large-scale brickwork/blockwork and concrete works as applicable to building works.
- Concentrate on the completion of roofs and roofs being covered before peak time.
- Try to leave any fixing or interior works as long as possible during late autumn such as plastering works, repairs or alteration works etc.
Precautions to take during Frosty periods
- Extend curing time or accelerate the hardening of concrete.
- In severe frost, where concrete is being done, consider heating the water and aggregate and mixing in close proximity to the job.
- New brickwork, blockwork, formwork moulds and reinforcement bars should be covered and protected.
- Consider wind breaks for mixing bays, and try to get work done, quickly, particularly those jobs associated with the trowel trades such as plastering.
- For trowel trades, also monitor temperature levels using the guide tabularized below
|0oC||Water freezes and hardening of concrete and mortar stops|
|4oC||Minimum temperature for placed concrete and mortar|
|10oC||Rate of hardening is reduced below this temperature level.|
|13o to 25oC||The best temperature range for concrete and mortar.|
|30oC||Too high temperature for concrete and mortar which may result to flash setting.|
Precautions to take during Extreme Sun periods
- Provide damping down or cover to guard against premature drying of concrete work.
- Provide sunshades for workers working in hot and dusty conditions.
- Provide means to protect materials in the event of breaking of good weather.