Lifecycle of Clay Roof tiles

The Building research establishment suggest a clay and concrete tile have a similar lifespan. Manufacturers will normally guarantee the tiles for 30 years with a 60-year life expectancy. As the BRE is the preeminent body with regards to building science and testing. This links to the British Standard as this will also fed into the calculations as they will define permeameters such as porosity with a seepage tests for example.

Bristol

If you look around Bristol there are countless clay roofs that have exceeded this. After the Second World War clay tiles fell out of favour as concrete tiles were more hard wearing and easier to produce. Hence the majority of the clay tiles that you will see are at least 70+ years old. Which is a above the expected lifespan. Even when a roof has been re-felted and the clay tiles reused they are often in poor condition. The surface is normally pitted and they just tend to progressively get worse.

Likely if a re-used clay tile was tested in the same manner as a modern tile they would fail. For one the levels of porosity would be such that the felt beneath would be doing much of the work. The tiles are supposed to be the primary method of keeping water away from the felt and habitable spaces beneath when they become too porous the roof’s integrity relies on the felt. Felt is not designed to be kept damp for prolonged periods especially modern felts.

Reactive vs proactive again

When re-roofing a property most people do not think about the long-term ramifications. It Is likely that the desire to re-roof is not one of arranged proactive maintenance. A leaking roof needs to be done quickly. It is often an unexpected expense and a very significant one . The idea of spending thousand of pounds to supply the new tiles required for a roof is often one that cannot be readily afforded.

The trades perspective

From a roofer’s perspective it is much easier to remove the tiles from the roof and stack them on the scaffold prior to relaying them. The alternative is to arrange a skip to dispose of the old, buy and deliver the new. Then the labour to bring the tiles from the ground up the scaffolding and stack ready for use.

From a roofer’s perspective it is fairly easy to persuade a customer that the old tiles will be acceptable. Just simply change out the odd one when it gets broken. That being said when the occasional tiles that will get broken during the re-roof the match is unlikely to be exact. This is due to differing brands of tile that are ever so slightly differing in their profile. This means that the tiles do not overlap successfully, as the supply of reclaimed tiles is dwindling this is becoming more common.

Life cycle replacement

Life cycle replacement costings

Verge needs replacement
Wet verge

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.

Life Cycles

Life Cycle Window external beading with gap
Window external beading with gap

Life cycle

There are numerous institutes who calculate life cycle data for the various products and elements of the building. The Building Research Establishment is the pre-eminent source for this data. There are further studies funded by other bodies such as the British Plastics federation and insurance companies. Windows are a good example with a basic google search highlighting almost 30 million results for life cycle of plastic windows.

When surveying it is important to consider the life cycle of the materials involved. This can help us give a time estimate for how long an element may last. This will help our clients plan for the future and potentially when they may need to replace the item. As well as help us report on their condition.

An example

This is when it starts to get complicated as for example the window maker Everest suggests an expected lifespan of 20 years. Whereas the Federation of master builders suggests 35 years. Historically the BRE guidance suggests 25 years but a recent study funded by the British Plastics Federation has made them stretch this to almost 35 years.

When calculating the life cycle of a material it is important to remember who is funding this research and why they may be funding this research. Again, using the example of windows the British Plastic Federation have a marked interest in attempting to suggest a longer life span. Their members will sell more products! Also, the materials and workmanship used in the testing of these products is likely to be much higher than that that would be found in the real world. If you live near the coast for example metal components will corrode much faster. There is also maintenance considerations, has the item been well maintained or not.

The best real world data comes from experience. This is why it is important to have an experienced surveyor look at a property. Again, looking at windows for an example we generally do not see windows operating correctly/efficiently after around 25 years. At this point the frames may be externally beaded. A security concern. The glass is not e-coated so does not perform as well thermally. The metal components will likely be suffering considerable wear and corrosion. The seals will likely have failed around the glass and the frames by this date.

When to test

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.

Electronic Radon Detector

After the previous blog on our experiment, we thought we could follow this up with the use of an electronic radon detector meter. We read various reviews, the one with the highest reviews was the “Airthings Corentium home radon detector”. However, most of the negative reviews related to the fact the machine wasn’t working on arrival. We paid £108.00 for it on Prime Day but without was £169.00. It visually appears identical to the “Canary” which from PropertECO was £165.00.

Ours arrived on Amazon Prime and worked straight out of the box. It stated the detectors in the meter were the work of the CERN laboratory, which gave us confidence.  It took a few minutes to self-calibrate. We purchased this meter to see if we could get a snapshot during a survey. To see if during the 4-5 hours spent on site would be sufficient enough for us to gain any meaningful reading. This meter takes 24 hours to give the first readings. So, using it in any less of a time frame than 24 hours is not possible. So, no use to a building surveyor doing residential work.

From a homeowner perspective however to be able to get some sort of meaningful results in 24 hours without having to send off for a 10 day laboratory test could be a great advantage for the short term needs of a property purchaser in a high risk Radon area.

Seasonality

The laboratory tests offered a seasonally corrected value. As the electronic meter was used after the laboratory tests. It was exceptionally warm during the second test period. hence doors and windows were open. This does appear to confirm that winter readings will be higher than summer readings by a significant margin. This will be a subject of a different blog.

 Unseasonably corrected laboratory analysisElectronic Meter readingdifference
Solid floor 1950’s543519
Suspended timber 1926421230
Conclusion

So the results do show a fairly major difference. We expected them to be proportionally different but that does not appear to be the case.

Our Radon Experiment

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.

Radon results
Radon experiment

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.

Should I get Radon Tested?

What do you do about Radon.

Ask if the property has been tested, is a fairly easy one top start. Given that since 2002 radon has been raised as a compulsory question in standard local authority searches. It may well have been tested already.

If it has been tested interpreting the readings may be challenging. The units are measured in Becquerels per cubic meter. In essence the average levels in UK houses is only 20bq/m3. That being said the lower the levels the better. The government has endorsed a recommendation that when 200Bq/m3 is reached then levels need to be reduced. Interestingly under the Health and Safety at Work Act the legal duty on an employer and workplace buildings is set at 400Bq/m3.

It is good practise that even when the property has been tested and remedial measures put in place then the property is retested afterwards. This could be interesting; as new properties say post 1999 or extensions constructed recently may have had the detailing installed but may not be functioning properly for example.

How do I know when to get a property tested?

The NRPB (National Radon Protection Board) suggests that when the risk is low 1-5% chance of the property having an issue, the purchaser may simply risk the small chance that they may have to spend money later reducing the amounts of radon in the building. However, it is suggested where the risk is higher say 10 -30% then the purchaser may want to protect themselves.

If testing has not been carried out you could consider re-negotiating the price to account for any remedial works that may be required. Such as installing the radon barrier and sump with electric fan. Installation of a positive input ventilation system (PIV) system. You could simply accept that the cost of the property is plus the cost of any remedial repair work required.

Legal advisors may be able to offer a service such as a radon bond or a Radon Retention. Where an amount of money is taken back the purchase price until the test results are received. If the levels are acceptable, the money is released back to the vendor. If the readings are excessive then the money is released to the purchaser to pay for remedial work.

Radon Part 2

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.

Radon Part 3

What do you do about Radon and the compulsory question?

Since 2002 Radon has been raised as a compulsory question in standard local authority searches. So an easy way to deal with this is to ask if it has been tested.

Interpretation of readings

If so, interpreting the readings may be challenging. The units are measured in Becquerels per cubic meter. In essence the average levels in UK houses is only 20bq/m3. That being said the lower the levels the better. The government has endorsed a recommendation that when 200Bq/m3 is reached. Then levels need to be reduced. Interestingly under the Health and Safety at Work Act the legal duty on an employer/workplace buildings is set at 400Bq/m3.

It is good practise that even when the property has been tested. Then remedial measures put in place then the property is retested. To ensure the levels have been reduced. This could be interesting as properties say post 1999 or extensions constructed recently may have had the detailing installed but may not be functioning properly for example.

The NRPB suggests when the risk is low 1-5% chance of the property having an issue. The purchaser may simply risk the small chance that they may have to spend money later on reducing the amounts of radon in the building. However they suggest where the risk is higher say 10 -30% then the purchaser may want to protect themselves.

What is it has not been tested

If no testing has been carried out you could consider re-negotiating the price to account for any remedial works that may be required. Such as installing the radon barrier and sump with electric fan. Installation of a positive input ventilation system (PIV) system can also be beneficial. You could simply accept that the cost of the property is plus the cost of any remedial repair work required.

Legal advisors may be able to offer a service such as a radon bond or a Radon Retention. This is where an amount of money is taken from the purchase price. It is held back until the test results are received. If the levels are acceptable. The money is released back to the vendor. If the readings are excessive then the money is released to the purchaser to pay for remedial work.

Radon Part 1

If we mention asbestos in our surveys, panic tends to ensue. With 5000 excess deaths a year related to asbestos. Mainly in the male dominated construction industry. If you were to mention Radon, we tend to get a blank look but research suggests it does contribute to over 1000 deaths a year.

If you live in a house in a geographic area affected by Radon, then you will be at higher risk and remediation works may well be required.

What is Radon

Radon gas is a colourless gas that emerges from the breakdown or decay of radioactive uranium in the ground. Other health factors are at play potentially Covid or a history of smoking may well influence the susceptibility of the human body to radon.

Radon in Bristol

Certain areas of Bristol are more prone to it than others, with the bedrock geology being the driving factor with for example the British Geological Survey suggesting areas in Bristol that would be affected more than others are the Inferior Oolite group and Carboniferous Limestone members. With certain parts of Clevedon generally showing that over 30% of properties may require some levels of remedial work. Whitchurch in South Bristol again showing higher levels. Whilst conversely parts of Stoke Gifford are showing at less than 1% require remedial action.

This website breaks it down to some extent. But the lines used in the mapping data are not exact. As you can imagine radon does not leave the ground in straight lines, so this over simplified model may well give a false positive impression.

My personal favourite is the below screen dump which over the period of 5 days changed rather significantly which is not helpful mid purchase. So you should also be aware that the readings for a particular area can change.

Radon
Radon

Considering the excess death risk. You would have presumed there would be some easy-to-use resources to help you determine your potential exposure and risk levels. The sad answer is no. The only way to do this is through monitoring the property. There is a video from PHE (public