Having roofing work done on a home can be one of the most expensive costs for homeowners. If the work is done well it can keep your home protected for decades, if done wrong it can be a costly ongoing pain in the neck for many years. Unfortunately, there is an increasing number of cowboy general contractors in the UK that don’t have the experience so make avoidable mistakes that end up costing homeowners time and money.
Why do general contractors get roofing wrong?
Most general contractors take on work that they are not specialists in, roofing work requires skilled roofers who fully understand the complexities of a roof and the installation process. General contractors take on large projects that include all aspects of the home such as brickwork, roof, electrics etc. This “we can do it all” approach leads to decisions that compromise quality and safety.
Have you had some renovation works completed and noticed water marks on your ceilings? Or had a roof installed on a new extension and water is pooling in the middle? These are common signs that the roof installation is of poor quality and vulnerable in certain areas.
Poor Roofing Material Selection
A common issue of general contractors is that they get it wrong when choosing the roofing materials, they don’t have the same knowledge of the material as an experienced and skilled roofer. This leads to malfunctioning and water penetrating gabs and faulty areas.
- Wrong material for area: Some roofing materials are not appropriate for certain areas. For example, general contractors occasionally install metal roofing on homes by the coast, metal roofing sheets do not have adequate corrosion resistance so the coastal salt air speeds up deterioration and leads to premature failure.
- Underestimating weight: Roof tiles come in all types of styles and weights, 1 on their own might not seem like much but when you have thousands on your roof this can put your roofs structure under strain. Installing heavy concrete tiles on a roof structure that can’t support them causes sagging and structural stress.
- Appearance over performance: General contractors do not understand the performance of the tile options and often agree to go with a certain material based on appearance. Choosing a roofing material because it looks better rather than its performance can lead to the roof not performing as well and needing repairs or even replacement sooner.
Example: A study was carried out in 2021 and it found that 24% of premature roof faults on new installations were down to poor material choice.
Inadequate Ventilation
Proper roof ventilation is pivotal to ensuring proper airflow into your roof as it helps to prevent moisture buildup, mould, and rotting.
- Blocked or missing vents: General contractors often do not know how much ventilation is required so don’t install enough roof vents or over fascia vents.
- Incorrect balance: Exhaust and intake must be correctly balanced otherwise it can cause negative pressure that leads to trapped moisture.
- Improper loft insulation: Building regulations state that a certain level of insulation must be installed in the loft to ensure adequate energy efficiency. If not enough or too much insulation is installed it can lead to your loft getting too hot or letting out heat in the winter.
Ask yourself: Does your loft become extremely hot in the summer and has moisture on the underside of your roofing felt and rafters? If so there is not enough ventilation in your roof.
Improper Flashing Installation
Lead flashing plays an important role in keeping joins on your roof watertight. Areas such as the chimney, dormer windows and joins to the wall all require flashing. Lead flashing is a specialist skill of its own and even some roofers are not fully trained. Due to its nature of covering joins and vulnerable errors, if not done properly will lead to roof leaks. This is why it is essential that you know how to choose the right roofing company for the work instead of using a general contractor.
- Over-reliance on sealant: Flashing should be fitted in a specific way and cemented for long lasting water protection. General contractors often use caulk and sealants that break down with weather exposure.
- Missing step flashing: Chimneys and dormers need step flashing to correctly protect the area, if not done correctly water will drain and get in the gaps.
- Incorrect lapping direction: Everything needs to lap each other in the correct direction to ensure water flows over the flashing and not under.
Real case: A homeowner in Norwich had to pay out a total of £10,000 in external and internal repairs because the general contractor they hired wasn’t trained in lead flashing installation so water got in around two dormer windows and caused water damage over several months. This is why your roofs need extra attention and care.
Ignoring Manufacturer Specifications
Depending on the pitch and size of a roof certain roofing systems have to be installed in a specific way to get the best results or even function properly. General contractors are often unaware of the requirements of roofing systems or overlook them completely in favour of shortcuts.
- Incorrect batten and nail placement: Roof battens and tiles need to be fitted in a certain way to meet building regulations and to perform correctly, any inconsistencies will lead to poor performance.
- Improper underlayment use: Using incorrect waterproof membranes on different roof pitches can lead to water pooling and leads to leaks.
- Not meeting overlap requirements: There can be no misalignment at all when it comes to roof installation otherwise water will not flow correctly and through gaps.
Roofing material manufacturers can sometimes void warranties on materials if they were not fitted to the correct guidelines, this means you will have to pay for replacement materials and to get them fitted again.
Rushed or Inexperienced Labour
When a general contractor takes on too much work they start to rush to get the job done quicker and can get paid, rushing roofing work will only sacrifice on quality and lead to roof leaks later down the road.
Undertrained workers: Not all general construction workers are qualified and although may have worked on roofs before, Roofing requires skill and expertise to be able to carry out professional installation.
- No supervision: General contractors often delegate roofing tasks to labourers or subcontractors without monitoring the work.
- Ignoring weather conditions: Certain roofing materials can only be installed in the right weather conditions, cold weather conditions stop materials like GRP from drying and the rain can cause cement work to run.
Industry insight: Statistics from NHBC report that 40% of roofing issues on UK homes are due to poor workmanship.
How to Protect Yourself from Costly Roofing Mistakes
The first step to ensure you get quality workmanship and avoid costly mistakes is to hire the right contractor for the specialist jobs, being proactive can save you thousands:
- Hire a specialist roofer early on to assess your roofing requirements.
- Request method statements and material specs before work begins.
- Demand installation photos so you can see the journey of work being carried out.
- Use warranties smartly: Ask for both material and labour guarantees to cover you if something goes wrong.
- Insist on post-installation inspections by third parties for a varied opinion, you may even need to get building control to take a look.
Final Thought
Roofing mistakes can be hidden until bad weather arrives or you start to see leaks internally. Poor planning, rushed work and lack of expertise can result in expensive repairs.
are expensive. They’re often invisible until it’s too late. Many arise not from bad intentions but from rushed timelines, poor planning, or lack of expertise.
If you are looking to get construction work done for your home or business make sure to speak to the right professionals for each task rather than trust one general contractor to manage it all to save costs. Every pound you spend on doing it right the first time saves much more down the line.