East Anglia: 01353 661222

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Useful Local Information

Martin and Mortimer believe that local as well as expert knowledge is crucial.  We offer general advice about some of the issues affecting property across our region (in particular, Norfolk, Suffolk, Cambridgeshire and London).  If you have any queries and/or would like to know more please feel free to contact us.

Thatched Property

Listed Property


Radon Gas

Cavity Wall Ties


Cavity Wall

Coastal Erosion

Thatched Property

With the advent of Listing and an increased interest in housing and conservation, the use of thatch has steadily increased over the last 80 years or so.  There are two main thatching materials in use in East Anglia: Norfolk Reed (water reed) and longstraw. Sedge is principally used in ridging.

Norfolk Reed

Norfolk Reed is used extensively in East Anglia.  It is the most durable of thatching materials. 
A Norfolk Reed roof will probably have a life span of 40-50 years although this will depend on environmental factors.

A Norfolk Reed roof is laid directly on to the roof structure.  In other words, the existing thatch is totally removed.  Consequently, the thatch tends to have less depth to it.


This has long lengths of straw visible on the surface.  Longstraw thatch also has 'liggers' visible (to the roof edges), not normally seen with Norfolk Reed thatch.  There will be netting over the roof surface to prevent birds from attacking the thatch.  This material is less durable than Norfolk Reed and depending on environmental factors will normally last around 25 years or so.  Longstraw is also commonly known as Wheat Reed.  There are different names to reflect the different way in which the material is applied to the roof.  When rethatching with longstraw, only the top layer of thatch is removed.  Consequently, the thatch tends to be thicker than a reed thatch.


This takes the brunt of the weather and will usually need to be replaced every 15 years or so.  Longstraw thatch usually has a longstraw ridge.  Norfolk Reed thatch will generally have a sedge ridge.


Thatch is not only a good insulator; it also sheds water very effectively.  Contrary to popular belief, it is no more prone to fire than any other material.  In fact, because owners of thatch properties tend to be very careful and mindful of fire risks, the incidence of thatch fires is actually very low.

Listed Property

What is a Listed Building?

A building is listed when it is of special architectural or historic interest considered to be of national importance and therefore worth protecting.

There are 3 listing designations:-

Grade I - Accounts for approximately 2.5% of listed property. 
It includes buildings of exceptional interest.

Grade II* - Accounts for approximately 5.5% of listed buildings. 
It includes buildings of special interest.

Grade II - Accounts for approximately 92% of listed buildings. 
It includes buildings considered to be of national importance.

What are the consequences of owning a Listed building?

Changes to the internal or external fabric of a Listed building (including structures within the grounds) may require Listed Building Consent.  If the changes are on a 'like-for-like' basis only, consent may not be required.  There are no hard and fast rules.  You should therefore, before undertaking any works, meet with the Local Conservation Officer and discuss what will need formal consent.

Making alterations without consent may lead to criminal prosecution with penalties including imprisonment, fines and orders to reverse the work carried out.

Alterations requiring Listed Building Consent may be exempt from VAT.

Are there grants available?

In exceptional cases, grants may be available from English Heritage.  Buildings are considered on their individual merits but you are unlikely to obtain a grant for anything other than a Grade I or Grade II* Listed property.

On a final note

Before purchasing a Listed Building you should obtain your own survey.  Martin and Mortimer have a long history of surveying and valuing period houses.  It is important that your chosen surveyor knows what he/she is looking at and that they are conversant with the use of building materials at the time the property was constructed.  The use of modern materials on a period property can lead to problems.

Non-Traditional Housing


Non-traditional housing includes system built concrete, timber/asbestos and steel framed houses.  Many were built in the post-war period (1947-1956) but there are examples from the very early part of the twentieth century right through to the present day.

Early prefabricated houses

Many of these were of timber framed construction with asbestos and/or cement and straw boards.  There are still examples in Cambridgeshire and Norfolk.  Some have had external brick skins added and this can make identification very difficult.  Many of these early examples were single storey dwellings.  These property types are unlikely to be mortgageable.

There are, of course, period and modern timber-framed properties which are perfectly mortgageable.

Steel framed houses

There are examples of steel framed houses from the early 1920's right through to the late 1960's.  Some new houses are built around a steel skeleton.  The early examples (Dorlonco and BISF houses, etc.) do have some inherent issues but later examples (Trusteel, etc.) are generally mortgageable.

PRC Houses

These are essentially of pre-cast reinforced concrete (PRC) construction.  The properties were designed to be constructed quickly in factories built for post-wartime production.  There was a significant shortage of homes as a consequence of bombing and inactivity in house building during the second world war years.  There are a large number of PRC house types and distinguishing between them can be very difficult, even for a trained surveyor.  Some of the more common types in East Anglia include "Wates", "Airey" and "Unity".

Many of these PRC houses have been designated as 'Defective Dwellings' and are thus generally not mortgageable.

There are some concrete houses which are mortgageable; these are generally large panel systems or post 1945 'poured in-situ' concrete construction types.

Defective Dwellings

Following a serious fire in a PRC (Airey) house type, structural defects were identified and concerns grew that similarly constructed properties might also be affected.  As a consequence, during the 1980's the Building Research Establishment (BRE) was asked to investigate all PRC houses.  Subsequently, a large number of PRC property types were designated and 'Defective Dwellings'.

Many of the PRC homes which were designated as defective were local authority built and owned but some had been sold under the councils' 'Right to Buy' schemes.  Grant funding was quickly put in place (for a limited time period only) to repair PRC properties that were in both public and private ownership.  These grants are no longer available to the public.

An unrepaired PRC home is unlikely to be mortgeable through normal lending sources.


Not all prefabricated property is necessarily unmortgageable or defective.  It depends very much on the type of construction and whether a formal, approved scheme of repair has been undertaken.  It is not always obvious to the lay person that a property is prefabricated or whether it may be classed as a 'Defective Dwelling'; all the more reason to have a survey.

And the Future...

Prefabrication has not gone away.  Timber 'kit' houses can still be purchased and are very popular with self-builders; steel often forms the loadbearing element of new property.  Prefabricated (and modular) structures are very popular in many European countries and the trend will, to some extent, be reflected in England in the future.

Radon Gas


Radon is a naturally occurring gas which is believed to have been a cause of lung cancer for many years.  In the light of this potential risk, the Government accepted advice from the Health Protection Agency (HPA) (now known as Public Health England) to commission a survey to identify those areas of the country with higher than average levels.  We have access to these detailed maps and can give you guidance as to whether the property you are thinking of buying is in an area that is potentially affected by Radon.


Indoor radon concentrations are dependent on various factors including geology, building construction, and the individual habits of the property owner.  There can, however, be wide variations on the radon level in individual properties within an area with above average radon levels.  A simple and inexpensive detection kit can be purchased although the minimum testing period is three months.


Where high concentrations of radon have been identified, the aim is to reduce those levels in existing homes and to construct new property with precautions against radon.

Remedial work

Radon enters a building from the ground and unless remedial work is carried out or there are precautions in place, it will collect in the building.

There are passive and active methods of treatment.  The passive system comprises an air-tight barrier below the property (usually the preferred method in new buildings). The active system comprises natural or mechanical underfloor ventilation, or an internal extraction system.  Clearly, there are some small running costs associated with the active systems.  Sometimes passive systems need to be supplemented with active protection methods.

Simply opening windows is not effective but there should be trickle vents over window units.  There is no proof that solid downstairs floors provide any more protection than suspended timber floors.


This will be very much dependent on the size of the property and the measures required.  There will be costs for installation and running costs and you should always obtain estimates from a specialist.

Cavity Wall Ties

Did you know that over half the building stock in the UK is of cavity main wall construction?

It is surprising how many people have no idea how the property they live in is constructed, let alone the one they wish to purchase!  In broad terms, most houses which were built before 1935 have solid brick external main walls.  After this time, the trend, increasingly, was for the main external walls to be built in 'cavity' form (a wall with two 'skins' and a gap/cavity in the middle).  Initially, both 'skins' (or 'leafs'), were formed in brick.  As building regulations changed over time, it became increasingly more common to build the inner 'skin' (or leaf) with blockwork, so as to improve the thermal (heat retention) qualities of the structure.  Sometimes the gap/cavity was filled with a variety of additional insulation materials such as foam, blown glass fibre, or polystyrene beads.  To hold the outer and inner skins/leafs together (and maintain the structural integrity of the wall) metal wall ties would have been inserted at the time of construction.  In more recent years, metal ties have been superseded by stainless steel and plastic wall ties.

Research which has been carried out by the Building Research Establishment (BRE) has identified that some cavity walls which were built before 1981 MIGHT be prone to metal wall tie corrosion.

The problem with some metal ties is that over time they corrode.  Eventually, if left unnoticed/untreated, the ties will fail.  If too many ties fail in the same area of a wall, partial/total collapse could occur.  To complicate matters, a variety of wall tie types have been used in the building industry over the years.  Are they all at risk of corrosion?  After realising that there was a possible problem the Government commissioned the Building Research Centre (BRE) (an independent buildings research organisation based at Garston, near Watford) to investigate.

Do you live in a house that is at risk of having cavity wall tie corrosion?  Are you proposing to buy a house that might be at risk?  What are the causes of cavity wall tie corrosion?  What are the symptoms?  What are the remedies and the costs involved?

The results of the BRE research may be summarised as follows:

(1) Cavity walls which were built before 1981 are potentially at risk because the metal wall ties often lacked adequate protection against corrosion.  After 1981 metal wall ties were more thoroughly protected and stainless steel/plastic alternatives introduced.

(2) Some pre-1981 metal cavity wall ties are more prone to corrosion than others. Generally, the older the cavity wall tie, the greater the risk.

(3) Cavity wall tie corrosion is exacerbated by environmental factors.  Proximity of a property to industrial (airborne) pollution or exposure to salt air (cliff-top/seaside) will increase the risk of wall tie corrosion occurring.

Put simply, if you are purchasing a property with cavity external walls which was built before 1981 and is located in an industrial town or close to the sea there is a potential risk of wall tie corrosion.  Unfortunately, the first signs of a problem usually happen at a later stage, when wall tie corrosion is well-advanced and the structure is beginning to fail.  Horizontal cracking occurs along the brick courses where the wall ties are located. Bulging in the wall occurs due to expansion of the metal ties within the wall.

If a problem IS diagnosed, the remedy will take the form of inserting new steel or plastic wall ties next to the old ones.  If the old wall ties are of the 'vertical twist fishtail' type, they will have to be removed and this will, potentially, double the cost.  If the defective wall ties are of the 'butterfly wire' type, they can be left in place and allowed to corrode merrily away.

Martin and Mortimer will advise, always, on the potential issue of cavity wall tie failure when carrying out a survey for a potential purchaser.  We will not carry out any invasive investigations through the wall structure as this is not something we can do on a property under separate ownership, and the extent of the investigation required is beyond the scope of a normal domestic survey.  We will, however, assess all the facts and use our experience and expertise to decide whether, before exchange of contracts, it would be advisable to have a CCTV inspection of the cavity wall ties carried out by an approved specialist.

Retrospective Cavity Wall Insulation

Why do people install cavity wall insulation?  To keep warm and save energy seems to be the normal response.  But does it really keep a dwelling warm?  Is a wet wall incorporating wet insulation material a good thermal insulator?

The answer is NO; a 'wet' wall equals a cold wall.  So how does that keep a dwelling warm and save energy?  It doesn't!

Cavities are formed for the sole purpose of keeping the weather out.  If not, they would be constructed with a solid wall, as they would be a lot easier to construct.  When retrospectively filled, the cavity wall to all intents and purposes becomes a solid wall.  The insulation can form a bridge and act as a carrier of moisture from the outer skin of the wall to the inner skin.

It has become widely accepted that, in certain circumstances, cavity wall insulation materials (of whatever type) which are retrospectively installed into an existing cavity wall don't really make a great deal of difference to the overall thermal insulation value of the wall, given that in a number of cases that have been investigated, the insulation was not installed to the required standards, particularly where large areas void of any insulation material were found.  With some systems (polystyrene beads), there were areas of obvious settlement.

If fitted either inappropriately or incorrectly, retrospective cavity wall insulation can lead to damp problems internally.

Surveyors should be fully aware of the problems associated with retrospectively introduced cavity wall insulation and should look for signs that it has been done and whether there have been any adverse consequences.

Coastal Erosion

'If I buy this property is there a risk of landslip?'  'Will I be able to sell the property in the future?'  'What should I pay for a property I really would like to buy and is it at risk?'  These are the most common questions we are asked when surveying property along the exposed north Norfolk coast.

It is hardly surprising that people are concerned about the issue of coastal erosion.  However, like many things, the problem can be blown out of all proportion, not least by sensational media coverage.  The sight of buildings falling into the sea on our television news screens does leave an indelible mark on the memory.

The truth is that there are large stretches of the Norfolk coast that are increasingly being left to mother nature.  Coastal engineers euphemistically call it 'soft engineering'. Certainly there are one or two 'hot spots' where there is a not insignificant loss of headland to the forces of the sea.  Happisburgh is a case in point; pockets of erosion also occur between Happisburgh and Sheringham.  There are also areas where the effects of poor land drainage need to be considered.

The important thing to remember is that notwithstanding the history of loss to the sea, the vast majority of coastal properties will remain totally free from danger for many years - long after our lifetime and (probably) the lifetime of our children and our children's children.  In Happisburgh, Trimingham and Overstrand (near Cromer), for example, there have been some dramatic cliff falls in the past 30 years.  However, the majority of the buildings in these villages lie well away from the cliff edge.  It would be quite wrong to 'write off' these locations as being' too risky' to invest in.

In broad terms (and subject to 'cost benefit analysis') in vulnerable coastal towns and villages where the building stock has a market value of significance the coastline WILL be defended to a greater or lesser degree.

The Coastal Erosion Officer (CEO) based at the local authority (typically, North Norfolk District Council) will be pleased to answer any of your queries should you have a particular property in mind.  The CEO will send you a map of the property and its immediate vicinity indicating where the coastline is predicted to be in 60 years' time (and later) - 'the blue line'.

The simple rule of thumb is do not buy any property which is located on the 'wrong' side of the 'blue line', OR consider paying much less for the property than you would pay for a comparable one which is not as risk.  Having said this, we know many clients who have been perfectly happy to acquire beach/cliff-top properties because of the wonderful views available, the exquisite fresh air, and on the principle that 'you can't take it to heaven'!

If you are thinking of buying a coastal property Martin and Mortimer will be pleased to offer general guidance on erosion matters and how these might affect market value, insurance and re-sale.

Head Office and Central Contact Centre

Bedford House, 26A St Mary's Street, Ely, Cambridgeshire, CB7 4ES

East Anglia: 01353 661222     London: 0207 416 6355