What is a coping stone?

Historic buildings often had open roof structures with no party walls in the loft spaces nor above the roof lines. If a fire did happen in a property on a terrace. It spread through properties very quickly. As a result, party walls in the loft space became more normal and the raised parapet became common normally topped with a coping stone. These raised parapet walls between houses are some of the character features we expect to see in Victorian era housing.

Why is it important

Where you put an exposed wall above the roof line. Dampness is not far behind. They form a natural weak spot between houses for water penetration. Originally, they would have been cast or cut stones fixed to the top of the wall with mortar. They were intended to help keep water out of these exposed walls.

The lower parts of the wall had to be rendered to try and keep the water out. These rendered sections were very hard to see from ground level and often failed as they were out of sight out of mind. Until the ceiling became damp. Then lead flashings and soakers had to be used to join the roof and the raised wall together.

This is a very complex way to create a roof structure. As it is complex any one of these components fail then water can penetrate into the loft and work its way into the room beneath. One of the most common failures are poor overlap of the coping stone over the wall. The NHBC give guidance for modern buildings suggesting a minimum overhang of 40mm. This is not often achieved. Especially if walls have been re-rendered.

Are they stone?

Older and higher quality buildings actually used stones. Normally limestone. If stone were subject to heavy weathering. This often-caused them to delaminate and spall. The thinner the stone the more likely water could penetrate through its thickness. As an example, is shown in the picture.

Coping Stones

Then came the cast manufactured stone, these were mainly concrete. These weathered better and were often triangular shaped to help shed water away from the wall. However, where the copings meet each other there was a slight gap for the mortar. So the quality of the coping was reduced by this mortar band.

How do you solve this?

Replacing the coping stones and detailing with a modern plastic damp proof course beneath is a an expensive but longer term fix for the issue. The damp proof course needs to be “fully bedded”. This means that the plastic damp proof course needs to be laid on a thin bed of mortar then the stone fixed on top with another layer of mortar. Effectively sandwiching the plastic. If not slight settlement/shrinkage will cause the damp proof course to lift off the wall. As can be seen in the picture below.

We often see now, that older coping stones on raised parapet walls, are covered over with leadwork. Although expensive this is a good way to deal with penetration through the stones. Again other modern materials have been used such as felt and fibreglass to water proof the top of the stone, these can be acceptable but have a more limited life.

Importance of Wall Thickness

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Wall Thickness

Spurred on by the interest in thermal performance and the impact of wall thickness we put together this video. As a result we should go into this in more depth. This does not include stone walls. That will be saved for another day.  So from a thermal and water penetration perspective of brickwork walls. Basic building bricks are porous. This defies sense to some extent in that you would presume bricks are water proof. Unless using a dense engineering brick, they are not. This is one of the reasons that dampness often occurs around chimney breasts.

Cavity walls.

As we stated on the video, a cavity wall can generally be seen by its thickness, over 300mm. the cavity wall is two half brick thick walls tied together. This gives the edge on damp penetration as water can saturate the outer leaf whilst the internal remains dry. There are issues relating to ties. Generally, this is the Rolls Royce of the residential wall world. These can be cavity filled to improve thermal performance. They are considered “average” under the EPC. They do perform very well from these two perspectives.  When insulated these are considered “good” for EPC purposes.

Solid walls.

As shown in the video these are 9” in thickness, but slightly more if rendered and plastered. These tend to be in imperial measurements as they are pre 1970’s. During the heavy storms in 2015 we saw a lot of these walls becoming completely saturated due to the intense, prolonged driving rain. This is very freak occurrence; however, many insurers declined the claims as they were considered penetrating damp rather than an event. Whilst structurally these are good they are failry slender and can distort for various reasons. From a maintenance perspective re-pointing is the general failure.  These are considered “very poor” from an EPC perspective.

Half brick thick walls.

These are very troublesome. We did a bit more on these in a sperate video that can be seen here. When they are brought into houses, they are often well hidden with deep dry lining and thick layers of render so are hard to spot. These perform terribly from a thermal perspective and condensation and mould related defects is one of the clues the wall may be half brick thick. We have seen properties declined a mortgage for example if the Kitchen is in a half brick thick extension. Structurally the walls are very thin and will bow and crack fairly easily under minimal loading or changes in soil condition.

Manipulation of pictures.

A picture says 1000 words.

As part of our desktop research, we always look at the agent’s pictures and floor plans before arrival. This gives us a good idea of what the property condition is like and what we need to look for. With returning clients who have sat through one of our feedbacks and understand the terminology. We will look at these pictures prior to them making an offer to give some feedback on potential issues. This is so that a property with significant issues, such as missing chimney breast or severe structural movement can be avoided.

There is no charge for this, as we want our clients to get the property that is right for them. As our reviews also show this. “Even before they conducted the survey they checked the history of the property, issues and concerns – this helped me decide, before paying any money out, that a property was unsatisfactory. This led to finding the (almost) perfect house.”

What we didn’t know.

We are friends with an agent in London and they mentioned during a conversation that they edit their pictures. This produced a long conversation as to how ethical this was. They said it was to touch up on various imperfections normally due to issues with taking pictures. Such as light and shade. They did say there was a service offered to make a property look lived in. They will add furniture and appliances to the pictures for a fee. This surprised us we had noted the increased use of fish eye lenses and such to give the impression rooms are larger than they are for example.

Is it ethical to alter pictures?

On our Facebook profile we were sent an advert by “Made Snappy”. Probably as our profile says we are in real estate. The advert states that well known estate agents such as Town and Country, Hunters and Martin & Co. use their services to touch up their pictures. Again, we did not consider this until we saw that one of the services offered was VC which we presume is vertical correction.

One of things that is most obvious in our initial looks at a building is leaning, where there is clear guidance under the BRE 251 digest. Until we saw the promotional picture used below. This begs the question how far is it ethical to touch up pictures, to hide movement? To airbrush cracks or damp spots? We will leave that for our clients to decide, but it could certainly cause stakeholders time involved in the purchase to be wasted. Should the pictures be marked to show they have been altered?

Pictures
Picture Manipulation

How to spot a Laing Easiform

Laing Easi
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At the moment we are getting large volumes of instructions for Laing Easiform properties. Laing Easiform offer a cheaper price point to enter the market. Also, we have published blogs and videos on YouTube about them. We also have the reviews to show for it.

“ He understands Laing Easiform properties really well and he is really passionate about his work as we could prove reading his elaborate report. He even gave us tips about the conveyancing process and things that had nothing to do with the survey! “

“We got a full structural survey done on a Laing Easiform and Jon’s expertise and passion really shone from the beginning. He advised us honestly and professionally and the debrief session after the survey was invaluable.”

Why do I need to know?

We often get sent links where an agent has advertised the property for sale. But there is no mention that it is non traditionally constructed. The first we see of it is the Zoopla or Rightmove link. Then we have to try and work out from one picture of the front what construction it is. Also is it worth taking the risk by informing a client. Based solely on one picture that their dream house is actually non standard construction.

This is very challenging for our back-office team. So, we thought we would list some good indicators.

Also Banks need to know for mortgage purposes what type of property they are lending on. Some will not lend on Laing’s built pre 1960.

Outside

Laing Easi Form constructions had one of the longest runs of production from between 1919 to around 1960’s/1970’s .So sadly don’t think all non-traditional properties were built in the 1950’s post war era. Most are rendered externally so if the property is fully rendered and there are no brick-built properties in eyesight this again gives another clue. However just to be tricky in Horfield/Lockleaze there are some brick fronted Laing Easi forms. Another clue is to look beneath the rendering at floor level externally to see if you can see the regular markings of brickwork.

In Bristol Laing’s are found in various areas but were always built as large estates. So if the style of the property is repeated continually then you know it is a council estate. One easy indicator and the agent should mention this is asked. Such as Lawrence Weston, Henbury, Lockleaze, Brentry, Southmead and Bishopsworth to name a few.

The best external clue is the chimney it is very tall and thin and often shows some horizontal cracking but will be rendered or in Bristol often painted red by the council. We have done a previous blog relating to Laing Easi chimneys Non Traditional Construction (Part 1).

Internally

Measuring the thickness of the wall in a cavity walled construction 1950’s era property the walls would be around 12” in thickness the wall thickness in a Post second world war Laing are around 9” so much thinner.

The only internal clues are thin Bathroom and Kitchen door opening as little as 640mm in width. The doors are very distinctive as being solid panel doors with four horizontal panels, but these doors are shared with say 1950’s era council properties generally.

The fool proof way is to enter the loft space and look at the party walls, these are very distinctive. This is what we use to ensure a Laing is Laing, as shown in the picture above. The poured concrete walls with a damp proof course and casting lines in the loft void are the only fool proof method of identification.

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New Build Snagging

Not my job mate!

New Build Snagging

We made a decision in 2017 that we would not longer offer to carry out snagging surveys. The last one we carried out took weeks of back and forth to arrange. Then a challenging full day of inspection. Followed by one day writing the report and referencing the NHBC guidance at each stage. Then another day creating a useable spreadsheet for the developer. The fees we charged for this were fairly minimal and meant there was no business case for continuing to offer this work.

The market

There were lots of firms offering snagging services at the time but the quality of these differed significantly. From basic “counting the screws in the hinges” to better quality. There were no trade associations linked to the quality nor benchmarking. So, there was no set standard. Hence ours which was far more in depth and referenced the standards, was massive compared to the volume snagging reporting firms. The prices were incredibly low, we did not know how a good job could be done for the money. Invariable a good job was not done. We see this when doing homebuyers reports of more recent housing and defects that have not been spotted now. With vendors dealing with the fall out

What changed

We were asked to visit a new build property for a returning client that we had done two older houses for previously and genuinely liked them. We only allowed an hour or two on site. So said we would have a nose round with them. What was found was shocking. Truly shocking. Uneven floors, walls out of true, poor detailing, cracking generally. The site agent assured us that these would be dealt with. The only way to sort the floor was to remove the Kitchen, a very costly and damaging exercise. This was all spotted with 2 hours. Here is a slide show of just a few of some of the issues we have found.

We felt the need for a better-quality professional service was required. There are other companies coming to this realisation. With well-known you tube channels showing the poor workmanship and corner cutting that appears rife, this has actually become comedy viewing.

What is the future for snagging surveys?

We teamed up with Gary. He is an ex-site manager with 30 years’ experience in Construction. Thus he became the perfect Poacher turned Gamekeeper. He has previously worked for the NHBC and is site manager trained. We have created our own bespoke document to able quick and easy delivery of the information in one annotated picture-based report. The RPSA must have been having the same thoughts as us. With this market dominated by volume house builders marking their own work. They have just introduced their own new reporting standard. Gary Has attended the recent training for this as well and can offer the RPSA version or our own bespoke

What is a ridge

Ridges- What are they?

The ridge is the apex of roof. This is the upper part where the two pitches meet at the top. Ridges are designed to close off the top of the roof and prevent water getting in and the wind lifting the upper rows of tiling. Roofs tend to get ignored if they are working. But when they fail a rapid response is required. So why not get to know yours.

Wet ridge

Traditionally these have been held in place with sand and cement or mortar. Depending on the quality of the mix used lasts between 20-25 years. Although we recently found one that had lasted some 45 years. The quality and life expectancy does seem to have dropped in recent years due to workmanship. The NHBC supports this with well over half of all claims on its warrantees coming from failure of mortar used on roofing. The first signs of failure often form with small sections becoming detached and cracks forming between the tile and the mortar. Often this can be hidden by moss growth. The other sign of failure is when standing far away daylight can be seen between the vertical gaps between the tiles. This is normally the sand and cement washing away due to a weak mix.

Storms and insurance

During Storms such as the recent Storm Arwen, the main areas of damage are normally the ridges. This is due to the failure of the sand and cement holding it in place. Many insurers will decline this as “storm” damage as the storm has uncovered a weakness in the sand and cement rather than being the cause of the weakness. Hence wear and tear. This is supported by many case studies from the financial ombudsman service. These case studies are interesting reading and if you are thinking of making an insurance claim for storm you would be well advised to read some on this link. Before making a claim.

Dry Ridge

Driven by the insurance industry there have been changes to the British Standard for pitched roofing. One interesting change involves the ridge tiles. The newer standard bought into force on March 1st 2015. This states that sand and cement alone is not sufficient to hold ridge tiles in place. They refer to mechanically fixed systems. These dry systems limit the need for repointing the roof every 20-25 years. They hold the tile in a plastic clip screwed into place. Below these are a comb type detail designed to help ventilate the roof as well.

Verges

Verge
Wet verge

What are roof verges?

In the surveying context, a verge is where the roof meets the gable or flank wall (or detached side of a house). It is the weather-proof junction between walls and roof. While surveying with the pole camera we get a good view of these! Sometimes they can be seen well from ground level if there are no houses in the way. On Youtube, we have uploaded a brief video outlining the various types of verges and you can find it here:  

Wet verge

This detail or component was normally finished in sand & cement. Exposed sand & cement details tend to have a life span of around 25 years before they start to crack and detach; in some newer builds, this seems to have been reduced to 15-20 years as a result of poor mixes. The underside of this detail is called an under-cloak. This was often made from boarding containing asbestos; otherwise sheeting or plain tiles were used. A timber “ladder” was built under this and these often slip or have rot issues. This problem normally manifests itself as a slight gap between the end tiles and the tiles right on the edge of the roof.

On later works, metal clips are embedded in the sand & cement; these overlap onto the tiles, clipping them in place The sand & cement literally does get wet, absorbing rainwater. It often encases the ends of the timber battens, which can cause these to rot. If the depth of the sand & cement covering is thin, the timber may become exposed which speeds up the decay process. Sometimes they are subsequently hidden beneath profiled UPVC boards as a quick fix.

Dry verge

A more recent innovation is the Dry Verge. Dry verges attempt to improve on the reduced lifespan of exposed sand & cement and come in two different common types.

We often see the cheaper and quicker-to-install type of dry verge, the “omni-verge”. This consists of a profiled, moulded piece of plastic which follows the line of the roof, to enclose the tile and wall junction. These can perform satisfactorily as long as they are well fixed. However, they are more vulnerable to wind damage and detachment than the wet verge. Visually they are not particularly attractive because they appear to be a cheaper option.

The Rolls Royce of modern verges is the cloaked verge. This uses pre-formed tiles cast at 90⁰ that match the profile of the tiles on the main roof. It encloses the junction well and does away with the problems of exposed sand & cement. These tiles are interlocked into the roof covering so are naturally a much better fix. There should be small plastic clips between each tile; often these fall out or are omitted and if that is the case, they should be replaced. And these pre-formed tiles give a great aesthetic finish to the roof!

Pole camera

Pole Camera
4 storey to check on the roof

How did it start

Since our first video on you tube in 2013 where we used a large aluminium pole to get up to 12m in height. This was hard wired from a camera with a long USB cable. The technology was in its infancy. We were early adopters. The pole was very unwieldy and only used on the larger taller properties we surveyed. So, we had a smaller 8m pole in regular use. We have used a pole camera on every survey since. However, the pole length grew to 10m fibre glass which was fine for 2 and 3 storey properties. We used a high-quality camera linked by wifi to pad on the ground controlled by the operator. The pole camera gives a unique view of some elements of roofs that you would not be able to see from the ground. We first did pilot schemes with insurance companies to use them in storm claims in around 2010. They are much slicker now.

How do surveyors look at roofs?

Traditionally it was through binoculars. These are still useful for close up examination of flashings and chimneys. They have fallen out of favour due to the high-powered nature of modern digital cameras.

Other surveying practices have started using pole cameras in the last couple of years intermittently. However, the pole lengths are often shorter 6-8m and will not get above chimneys for example. The camera quality is often basic web cams which give blocky images. The low-resolution images cannot be effectively zoomed in on for a better view of a defect.

The skill is not just taking the picture. The analysis of the defect is all important. Without skill and experience looking at these images’ things can easily be missed. The surveyor must have time to review the images carefully after the survey.

What’s next?

We have been looking for a more effective camera pole ever since to keep a competitive edge. This resulted in us using Carbon Fibre. This is strong and very lightweight and still remains stiff in even in high winds. The largest pole we currently use is some 55ft long. Although it has not used to the full height as this will easily do a four-storey property and chimney. Four stories are the limit of our insurance anyway.

Whenever we are seen with the pole cameras. The question of drones always arises. These cameras are better in wind and can get closer to the important eaves details as we discussed in this older blog.

If you are looking for a survey and the surveyors say they use these cameras. Check they are high resolution images and what height they can effectively go to.

Breathable felts

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Breathable felts

The history of breathable felts.

Breathable felts were first thought about in the 1980’s. They started in Germany as a result of changes in their building standards. The first patents were made in 1983. However, such felts were not widespread in re-roofing in the UK until around late 1990’s. They began replacing the plastic grey Monarfoil felts which caused significant condensation in roof voids (Sarking felt or underfelting through time – Part 3). So, if you see a white, blue or green felt in the loft you know it is a modern felt and less than 25 years old. It may not necessarily be a breathable felt, but it can help to give an indication of the age the roof.

Although breathable felts are the optimal product to use today, some modern felts are not breathable. These rely solely on lots of other ventilation details being present. This will help the roof to breathe and reduce the effects of condensation in the timber components of the roof.

What are breathable felts?

Breathable felts are very clever when correctly laid. They are very strong made from non-woven polypropylene. They are resistant to UV degradation. Although if left exposed to the elements will eventually shred or rip. This is why eaves carriers became best practice. Changes to the British Standard 5534 in February 2015 included these plastic trays that hold the bottom of the felt up where it meets the gutter.

The problems with modern felts.

The makers are very specific about what other details are needed. Although these differ between manufacturers. These may include ventilated ridges, or hips. Where an air gap is left at the top of the roof to allow for better air flow. Vented soffits where the soffits have grills to increase air flow. These are often omitted in the mistaken belief that breathable felt on its own is sufficient. We have made a YouTube video of what happens if these details are omitted. https://youtu.be/GNsB8qc-_ns

The risk of overstretching felts is another challenge for roofers. The felt should drape over the rafters and have some sag. Clearly a roofer doesn’t measure the sag on each piece of felt. It would take forever to install a roof, but 10-15 mm is generally acceptable. Remember that the purpose of roofing felt is to divert back into the gutters any rain that is driven beneath the tiles by the wind. The correct sag allows that wind-driven rain beneath the tiles to run down the felt without touching the wooden battens and causing them to rot. You should be able to get your hand between the felt laps; if you can’t, it is too tight. There are visual signs of this defect; mould growth to newer felts is a symptom of over-stretching. Once stretched this will shorten the lifespan of the roofing battens and the roof will require re-felting again.

Sarking felt or underfelting through time – Part 3

Modern Monarflex felt
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Sarking felt or underfelting through time – Part 3

The next development was in the late 1980s/ early 1990s when builders used a reinforced plastic felt called Monarflex Monofoil. Originally designed for commercial applications, its inherent strength saw it find its way onto residential developments and re-roofing projects. It is in essence a reinforced plastic type sheet. It is usually apparent as a light grey in colour in the roof void.

The composition of this layer remedied the problems of decaying found in older felts. It should have been popular for a great deal longer, however it did not deal with the ventilation issues. This didn’t allow the roof structure to breathe. It was also laid fairly taut, being stretched across the rafters, and this further limited air flow through the roof voids.

Related condensation issues

As this felt was non breathable, it suffered terribly from condensation related issues too. Water droplets formed on the underside and ran down to soak the timber elements of the roof structure. It was supposed to have a vapour layer (another polythene type sheet) installed at ceiling height. This would have reduced the moisture travelling upwards into the loft but it was rarely installed. The legacy of this underfelt in domestic housing was condensation !

Recently we inspected a property where Monarflex was present and a loft conversion had been carried out. The insulation below was wet to touch due to condensation forming in the hidden void.

Dealing with condensation in the loft void

Some actions can help reduce condensation levels in the loft void. The damp air may be removed at source with extractor fans.  The often-missing vapour layer at ceiling height may be installed. This would require caution around services such as downlighters, wiring and ducting. Holes would have to be inserted for these and the loft insulation would need to be removed and refitted/replaced. External provision such as vented soffits and ridge and hip detailing could be made. But if you are going to this length, then simply re-felting with a more suitable underfelt may be a better option.