Concrete roof tiles

As we have said previously is expected by testing that clay and concrete tiles have similar lifespan. If not slightly longer. As concrete tiles really became popular after the Second World War had only been regularly used for 70+ years. These again have an expected lifespan of 70 years. We have to be aware that here we are only talking about half lapped concrete tiles. With a suitable profile on a roof pitch of over 30°.

Bristol

In a previous blog 5 years ago (https://www.domesticsurveys.co.uk/2018/08/23/how-long-does-a-roof-last/) we had a concrete roof that was 68 years. The issue with this was the age of other components. The felt, the ridge, the verges. Given the age of the tiles. It would not be wise to re-use them hence they were replaced. Would the tiles last another 68 years? They would certainly not last 138 years. So even whilst the tile may not have reached the end of its working life other components very may well be. However, re-using the tiles to gain 168 years simply would not be feasible.

Hence when re-roofing the tiles need to be replaced.

Reactive Vs proactive

We are now seeing concrete roofs being replaced. In a proactive manner from local authorities. Even on fairly standard or suitably pitched roofs. However, due to low pitched roofs. These were very common in the 1970’s these are now showing significant felt failings. These are now requiring replacement after only 50-60 years. A good example of this is the 1970’s Trendle wood Park in Fishponds, where the roof pitches are very low. Many of these require or have been replaced.

The trades perspective.

It can be considered that trades need/want to guarantee their work. This is a real challenge when dealing with older roofs. They will often only guarantee their work. So if failing occur in other parts these would not be covered.

Trades will often suggest re-using concrete tiles. This is due to ease. They do not have to arrange for waste disposal and delivery of new tiles. They do not have to lift new tiles onto the scaffolding. The older ones can be stacked and re-used close to the roof. Making the job easier. To give some idea. There is a specialist machine called a “bumpa” as this job is so labour intensive. This is a conveyor belt to lift the tiles up two stories.

Life cycle replacement costings

How to use the data

One of the most common phrases we hear during the survey or as a result of a negotiation is that “it has been fine for the last 40 years so why does it need replacement”?

This sort of comment also tends to reflects that little or no maintenance has been carried out during that period. Martin in the office has come up with his own great answer to this. “If you were standing outside in the wind and rain for 70 years you would probably be a little bit worn out as well.”

This is also one of the common responses from insurance companies the item you are claiming for has reached the end of its working lifespan or the damage was caused by a natural breakdown of the materials.

Reactive replacement vs Preventative maintenance

This is when we start to get into very murky waters. When you look at large housing providers such as housing associations, charities or councils they will have maintenance plans. These are solely based on life cycle data. This is why you will often see them replacing roofs for an entire street rather than just the occasional house. They also tend to carry out timed conditions survey so every five years they will send a surveyor to look at a group of properties and see what needs to be done generally. This informs their maintenance plans. This also allows them to finance the required work and arrange their budget for the coming years. This is a preventive maintenance approach. Remove the item as it reaches the end of its working life in a timed fashion for less disruption.

There is certainly an argument often taken by many private landlords that we will replace it when it fails. Sadly, what tends to occur here is that when the item has been failing for a prolonged period It affects another building element. For example, a leaky roof can cause rot to the roof structure well before visual signs are apparent in the habitable accommodation. Then you have the additional cost of repairing the roof structure, replacing insulation, damaged room or rooms. This means that the repair can become a lot more expensive. As the saying goes a stitch in time. This is very true with buildings and as surveyors we see this all the time. We are usually the ones to flag up the defects.

Given the results of our last blog. This casts an interesting phenomenon related to radon which is the effect of when you carry out the test. The laboratory analysis gave a whole house property average and called it “seasonally corrected”. Whilst no doubt there is a complex formula behind this calculation, we wanted to see the differences and when it would be best to test.

Clearly in our previous blogs ventilation of a property seems to be key. Especially relating to subfloor ventilation and the use of positive input ventilation. The lifestyle of the occupant also appears to be important. Would you leave windows and doors open during the test period. If the weather is warm then windows would be open overnight for example.

The seasonable factor will also have a major impact on results. When we tested during the summer. The results were much lower than when we tested in the winter. So if you are commissioning a test, then you may wish to consider this. Our results showed a much larger change than the “seasonally adjusted” figures showed. So if you are purchasing during the summer the readings will naturally be lower than the benchmark 200bq/m3.

Then there are the much more complex factors related to the geology. Radon gas has a half life of 3.8 days and is water soluble. Given that half of UK radiation exposure is due to radon then the groundwater issue we mentioned in our first blog, have a bearing although a limited one. During the winter when the groundwater tables are higher they also have an effect on the levels of radon being released by the ground. The readings will be higher in winter.

Given this it would be sensible to test for a full 12 month. Rather than the usual three month or 6 month tests that are carried out. This is where electronic monitoring becomes a much cheaper and more accurate alternative. As a full 12 month sample of results would clearly give the correct reading rather than attempting to seasonally correct an average from a specific part of the year.

The Experiment.

As they was so little information available to surveyors we decided to try and undertake our own experiment. We ordered a three-month test kit from Properteco with two separate detectors from eBay costing around 35 pounds including delivery. Do not just rip open the packaging containing the meters as it will be needed later.

We wanted to find out if there were significantly differing levels of radon in two properties.

One with solid floors, compared to the other with suspended timber floors and adequate ventilation beneath.

The two properties were in Stoke Gifford one is a 1950s solid floor construction, The 50s property we do not think has a damp proof membrane present except for thin polythene beneath an engineered wood floor covering.

This house is around 100 metres away from a 1920s build with suspended timber floor with adequate air bricks installed around the perimeter. We installed both of the metres in the lounges of these properties at about 1.6 metre from floor level.

We were supposed to wait for three months.

Sadly four months elapsed before we sent the units back for laboratory testing. So a good hint is to set a reminder on your phone.

For the experiment this was comparative rather than quantitative.

The Results.

The 1950’s solid floored property returned “Raw Radon readings” of around 54 Bq/m3. Whilst this is a very acceptable reading higher than the UK average but within tolerance.

The 1926 timber floored property gave “Raw Radon readings” of a lower 42 Bq/m3. So again, very acceptable higher than the national average but much lower than the 200Bq/m3 where remedial action would be required.

Conclusion.

The solid floored property had higher level of Radon in the Building. This suggested that lower levels of radon will be present in properties with suspended timber floors than those with solid floors but no damp proof membranes. The floor levels are lower with the solid floored property with more contact with the ground and no ventilation beneath to remove radon at source.

What difference does the type of property have on Radon

Whilst the physical areas where properties are located, due to geology has been discussed in our previous blog. What has not been discussed is the actual property type. It may well also make a huge difference in the build up of Radon. In the previous blog we also commented on the number of deaths potentially caused every year as being 1000. During our further research the National Radiological Protection Board estimates that radon causes between 2000 and 2500 excess lung cancer deaths every year in the UK, almost half as much as asbestos.

What effect does Occupier behaviour have on Radon

Do you open windows regularly? Have you had extractor fans fitted and do you use them. Do you have vented suspended timber floors or solid for example. We will explore this in our next blog. If timber do you have sufficient sub floor ventilation? Do you have a positive input ventilation system installed? This is because when radon enters an enclosed space it can reach relatively high concentrations where there is inadequate ventilation. It can enter through holes or gaps in floors or walls, gaps under skirting boards. Around services and through cavities in walls so do you regularly maintain and inspect your airbricks and fill cracks.

Type of property

The BRE guidance does however suggest If you have a cellar or basement, you risk is increased, due to the larger surface area being in contact with the soil. But again, this is property specific. It will depend on how the subfloor is completed with a radon barrier or not. Is it bare earth for example. If you do have a cellar, remedial works will prove easier than with a very small sub floor.

For properties constructed after 1999, the guidance in the Building Research Establishment (BRE) guide 211 was heavily revised. With the geographical area of properties requiring either basic or full protection being increased. However it is possible that radon reduction barriers were installed in properties constructed after 1988. But this is normally on a case-by-case basis. Specific enquires of the builder and plans would likely yield some clues.

What to do now?

As the detailing seems so property specific the best way is to test for it. There are short term tests available between 7 to 10 days however these will only give a very limited overview. These short term tests should be considered when the property is in a higher risk zone. The limitations here are that the occupies lifestyle and time of year will affect the readings. Three months test are available and cost around £50. however this isn’t particularly helpful in the purchasing process to wait this long. There are electronic detectors available which seemed to give a day-to-day measurement but again this will be season and occupier specific.

If radon in the air was not worrying enough it is now recognised that some private water supplies can also contain levels of radon. Which must also be controlled. Such as water from private boreholes and radon areas needs to be periodically tested.