HI Technical Bulletin For registered members of the SAVA Certification Scheme
Issue 8 December 2009 © National Energy Services Ltd 2009
Welcome to Issue 8 of SAVA’s
This month:
Home Inspector Technical
Schrijver damp proof course
Bulletin. The bulletin focuses on Home Condition Reports and associated non-energy issues.
Readers' comments— case study Issue 7
We trust that you will find the
Ask the Expert
day work and we welcome any feedback you have about what you would like to
Do you agree with the Home Inspector?
The contents of this technical bulletin may supersede certain Scheme rules or
bulletin useful for your day-tosee covered in future editions.
Home Condition Survey—An update
requirements appearing in the Product Rules, Inspection and Reporting Requirements, training manuals or elsewhere. Members must therefore ensure that they have read and understood this document.
An index of articles covering Issues 1 to 8 of the bulletin is available on NES one Useful Documents
Schrijver damp proof course While strolling through a Suffolk
of rising damp. In the 1920s British
village recently the devices shown in
Knapen first marketed ceramic tubes
the photos below were noted on a
and similar tubes were tried as a
Victorian terraced house. Someone
solution to dampness affecting
inspecting the property for a presale
Westminster Abbey in the 1930s.
survey could be forgiven for thinking
Hydrotek–Wallguard, who still market
that the householder had attempted to
the ceramic tubes as a dampness
improve sub-floor ventilation by
solution, state on their website that
inserting airbricks at 450 mm centres
they carried out further maintenance
as well as having injected chemical
to Westminster Abbey using the tubes
damp proofing treatment as the
in 1997 (see www.hydrotek.co.uk).
devices are immediately adjacent to the plugged holes that have been
The tubes are made of what is
drilled to inject the damp proofing
described as a particularly porous
chemicals.
ceramic material. They theoretically work by drawing moisture to them
However, these devices are not an
from the surrounding masonry and by
over indulgence of air bricks providing
allowing the moisture to evaporate
improved sub-floor ventilation, but a
through the increased airflow within
variation on the porous ceramic tube
the tube.
retrofit damp proof course (dpc). Ceramic tubes (Photo 2 circled red) were an early solution to the problem
Photo 2: Example of a ceramic tube Photo 1: Example of the Schrijver System® installed to a terraced house in Suffolk.
damp proofing treatment installed to the walls of another terraced house in the same Suffolk village.
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HI Technical Bulletin © National Energy Services Ltd 2009
The tubes are set in the wall at a slight angle,
Unlike the Wallguard ceramic tube, the device
presumably to allow any moisture to drain to
is simply a cleverly designed ‗airbrick‘ that is
the end of the tube at the exterior surface of
installed into a specially prepared niche cut
the wall. However, BRE has commented that,
into the wall. There is not a porous ceramic
if the ceramic tubes draw moisture from the
tube that is intended to attract moisture in
wall:
the surrounding brickwork to it.
“…,they must also draw salts. It is difficult to see how any significant evaporation can take place. If the salts are hygroscopic, the tubes could perhaps feed moisture from the air into the surrounding masonry when external humidities are high. “Also, for the tubes to draw moisture from the surrounding structure, they must be more finely pored than the surrounding material. In general terms, the more finely pored a material the less permeable it is and the lower the evaporation rate from it,
―The function of the tube is intended...to act as a bridge of the cavity to the inner leaf, ensuring that the niche is sealed from the cavity.‖
unless the material is virtually saturated. In that case, evaporation would take place
The aerodynamically designed air brick apparently works by allowing dry air to flow through an opening in the element, encouraged by the protruding fin. This air is led directly to the two air chambers created in the wall (see Figure 2) that are separated by the fin. The second opening in the system causes a draught which leads to a drop in temperature within the niche and as a result a cold bridge is created. This happens because humidity is deposited on the coldest spot and is in turn transported outside by the natural airflow.
mainly from the surface and the nature of the material would be of little importance.” Source: BRE: ―Understanding dampness: Effects, causes, diagnosis and remedies‖, 2004, pp.161-2. Despite such expert opinion and the lack of any scientific evidence that they work, the porous ceramic tube has been marketed by various companies for 80 years or more. Hydrotek–Wallguard, (Figure 1) also market
Figure 1: The Hydrotek–Wallguard porous ceramic tube damp proof treatment.
the porous tubes as a green solution to damp problems suggesting that the tubes use no
In the case of installation into a cavity wall
chemicals (in contrast to injected dpc
the device does incorporate a ceramic tube.
solutions); no running costs (in contrast to
However, the function of the tube is intended
electro-osmosis systems); and no noise.
to act as a bridge of the cavity to the inner leaf and to ensure that the niche is sealed
Turning back to the latest variation (as
from the cavity. The maker claims that, by
illustrated in Photo 1, page 1), the claims of
the action of the increased airflow,
the company marketing this product,
condensation from within the house also
Schrijver Ltd, are slightly different. They
disappears. They claim that “The Schrijver
claim that it is a humidity regulating system,
System® is an essential factor in eliminating,
consisting of a stone element and, in the case
preventing and controlling problems caused
of installation to a cavity wall, the addition of
by damp. The multifunctional results (dry
a tube. Figure 2:
The Schrijver System®: 1. interior side of wall
2. exterior side of wall 3. first air chamber 4. second air chamber 5. cold bridge 6. ceramic tube 7. insulated cavity 8. non-insulated cavity red = dry air blue = humid air
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HI Technical Bulletin © National Energy Services Ltd 2009
walls and a decrease in the relative humidity
In addition the Schrijver device appears to
within the house) brought about by this
undermine the thermal efficiency of the wall,
system, means that you can achieve a dryer
in localised spots. This might be acceptable
and healthy living environment and a possible
at dpc level as it is below the internal floor.
decrease in heating bills.”
However, a quick perusal of the Schrijver
(Source: http://bit.ly/3uz92C)
web site also suggests that these devises are
We cannot confirm or refute these claims but refer you to the BRE comments above. However, the device raises more questions than it claims to answer. If the device is installed without inconvenience to the home owner, then
installed at upper wall levels in an attempt to cure dampness problems. Creating localised cold bridges could cause other problems such as interstitial condensation.
―The Inspector
Whatever the result, the fact is that those
needs to
inspecting property might encounter these
carefully
devices. It is therefore important to recognise that these are not airbricks
consider the
providing sub-floor ventilation but a
evidence of any
dampness cure.
damp meter
treatment. There is therefore a risk that salts
You should ask for confirmation of any
readings taken.‖
that have leached into the plasterwork will
guarantees offered by the installers, ask what
remain there, with all the inherent issues of
specific source of dampness the devices are
such contamination. This will also make it
intended to cure and you should consider
difficult for anyone using a moisture meter to
carefully the evidence of your own inspection.
verify if the wall is damp as hygroscopic salts
In particular you need to consider very
conduct the current passed through the wall
carefully the evidence of any damp meter
by the moisture meter, giving a ‗high‘
readings taken.
presumably the plaster is not hacked off at the internal wall surface and replaced with hard cement render etc, as would be the procedure with an injected chemical dpc
moisture reading.
Readers’ comments—case study Issue 7 A number of queries have been raised
A light growth might be power washed off
relating to moss growth on roofs—as
quite easily without detrimentally affecting
considered by the ‗Do you agree with the
the covering below but a heavy growth could
Inspector‘ section of Issue 7—where a rating
suggest something more sinister—where the
of 2 was applied after the Inspector had
moss may have started to break down the
followed the SAVA condition rating protocol.
surface fabric of the roof allowing water, or
The article considered that there was a repair
at least dampness, to penetrate the
required but that it was not considered
underside—thus affecting other building
serious.
elements.
Some respondents have felt that perhaps a
The prudent inspector must use his/her eyes
rating of 1 or 3 could well apply to the
(and binoculars), following the trail searching
situation.
for other potential defects which may result
When we consider such an issue we must
from the initial observation.
look to our own professional experience and
Photo 1 illustrates a light moss growth
indeed common sense, as we are duty bound
covering which, following the condition rating
to provide a fair and constructive report for
protocol, could produce a rating of 1 with a
our client.
general comment made about maintenance.
In the wetter western and northern parts of
Photo 2 (over the page) suggests that a
the UK, and indeed in the tree lined towns
serious issue could exist—with the possibility
and villages of middle England, moss growth
of the breaking down of the concealed tiled
on roofs can be a problem. The growth can
surface. By following the protocol this would
be light or in some cases it can virtually cover
certainly give a rating of 2 but could lead to a
a whole roof, particularly on older concrete or
rating of 3 depending on the other
asbestos tiled roofs.
observations made during the inspection,
Photo 1: Light moss growth.
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HI Technical Bulletin © National Energy Services Ltd 2009
with particular consideration given to other building elements such as the roof space and timbers, guttering and chimney stacks. Whichever decision is reached the Inspector must ensure that sufficient evidence is retained in the site notes to justify the rating in the final report. The photograph in the original article (Photo 3) suggests more than just a light growth but does not indicate anything more serious. Therefore, a rating of 2 with a
Do you agree with the Inspector? One of our readers submitted the following comments regarding our previous case study: “In my view, the rating 3 in D4 is excessively harsh. One could argue that the drilled holes would allow the damp-proofing (and wall) to dry out better! “I agree it is „good practice‟ to fill the holes and I would suggest a condition 2 rating would be fine.
general comment would appear to be the
“The other condition 3 ratings are justified.”
correct decision in this case.
Tim Green What do you think? Send your comments to bulletins@nesltd.co.uk
―The RICS Code of Measuring Practice must be
Photo 2: Heavier moss growth.
followed when measuring
Photo 3: Light moss growth; photo
buildings for
featured in original article.
re-instatement cost calculations.‖
Ask the Expert Question:
should it be assessed as an addition to the
In RDSAP an external porch is excluded if the
base model?
area is under 10% of gross floor area; but should I include an external porch area in the floor area for BCIS?
Answer: When measuring buildings for re-instatement cost calculations it is the RICS Code of Measuring Practice that is followed and not any divergent application of measuring practice such as the rules developed for RDSAP. Such deviations are relevant and specific to the calculation of the energy efficiency of buildings and not to other applications of the Code of Measuring Practice. So to answer the question quickly: the porch is measured and included in the floor area of the dwelling. However, this leaves a second question hanging: is the floor area of the porch simply Photo 1: Porch constructed in matching materials to main structure.
Technically speaking the BCIS Guide to House Rebuilding Costs is more or less silent on the cost of re-instating porches as separate items. Additionally there is no mention of porches in the basic specifications for the various house and bungalow models that the BCIS base figures are assessed from. Therefore, to answer the question in full we need to refer to the RICS Guide to Carrying out Reinstatement Cost Assessments. This document suggests that details of the different types of construction and finishes must be noted and costings for reinstatement must be based on these. In assessing whether to include a porch with the rest of the main building you need to consider two assumptions:
included as part of the floor area of the main
Firstly that the porch is constructed of
accommodation or, like a conservatory,
the same materials as the original
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HI Technical Bulletin © National Energy Services Ltd 2009
structure and to the same basic
―The cost of demolition and clearing away
specification.
of the existing structure, and rebuilding to
Secondly that the porch is not at odds with the specification and design notes incorporated into BCIS for each age and detachment type of building specified. Photo 1 shows a porch that although outside the basic rectangular building line of the semi-detached house is constructed in matching materials to the main structure and
its existing design in modern materials, using modern techniques to a standard equal to the existing property and in accordance with current Building Regulations and other statutory requirements.‖ In other words BCIS assumes that the rebuilt structure is actually different from the original. For example:
so could easily be simply assessed as part of
Windows will be double glazed whether
the main floor area.
they were or were not in the actual
If the porch is significantly at odds with either of these assumptions then the professional must consider if the porch should be separately assessed as an addition to the
building; the other U-values of elements such as walls, roofs and floors will be consistent with current building regulation requirements (Part L).
basic model. The form of construction (such
Likewise, because the building regulations
as that illustrated in Photo 2) might be better
now require the provision of sanitary
compared in certain circumstances to a
facilities on the principle floor (ground
conservatory if the walls and roof panels are
floor) to comply with Part M, the addition
glazed, or to a garden building if the
of a cloakroom will be incorporated in the
structure is a very basic timber frame.
calculation by BCIS as this is the easiest
However, in the majority of cases, the simple answer as to how to account for the porch in
Photo 2: Porch of significantly different construction to the main building.
way to comply with this aspect of the regulations.
the BCIS calculation is that the floor area of
BCIS provides specifications for each house
the porch would be included in the floor area
type that the base figures are founded on.
of the house and then the base rate for that
So if you look up the specifications for both a
type of property applied to the porch
Victorian and a 1970s house in BCIS you will
together with the rest of the structure. This
note that the sanitary ware includes two
is because most porches are small and
toilets; BCIS is assuming the provision of a
insignificant as a proportion of the building
separate toilet in a cloakroom on the ground
floor area. And a comparison of the cost of
floor irrespective of whether this would have
―BCIS assumes
reconstructing the porch as a proportion of
been typical when the dwelling was originally
that the rebuilt
the whole building compared to the cost of
built or not. This is why there is a problem
the porch, if assessed individually, is unlikely
changing from 1 cloaks to zero.
structure is
to be more than one or two thousand pounds difference.
The NHER HCR software (which interfaces
Question:
prevents you over-riding the minimum
There is a problem with BCIS not accepting ‗zero‘ for the number of cloakrooms in a house. I have had the same problem with a Victorian terrace and a 1970s semi. Can you help?
Answer: The answer to this question is to explain a common misunderstanding among property professionals of how BCIS calculates reinstatement cost. There is a very good reason for leaving the cloakroom count at 1. BCIS defines reinstatement cost as:
with BCIS) incorporated a safeguard that specification of one cloakroom. So do not panic! In the stand alone version of the BCIS software it is actually possible to change the cloaks count to zero, despite the program asking you if you are really sure you want to do that. However, the NHER version is protecting you from a potential claim by stopping you from providing an insurance reinstatement cost that is below the minimum specification.
actually different from the original.‖
Issue 8 Page 6
HI Technical Bulletin © National Energy Services Ltd 2009
Do you agree with the Inspector? This series focuses on the assignment of Condition Ratings for the HCR. The case for the current issue was send to us by John Priest. Do you agree with the Home Inspector?
However, on reflection, he writes: ―The damp course was now defective and no longer effective in the role it played at stopping damp penetration. “As stated in the IRR CR3—A serious
Let us know what you think. Send your
defect is one which compromises the
comments to bulletins@nesltd.co.uk
intended function of the building element-in this case, the damp proof
John Priest, a recently qualified Home Inspector has seen a house where the owner has installed a boiler in the cellar—nothing wrong with that in itself. The house is 1937-built with solid walls and a slate damp proof course. The location of the dpc can be identified by the extra depth of pointing. However, the installer has made a few mistakes. As can be seen from Photo 1,
―There is a
the installer has removed a brick in order to
need to seal
create a hole for the flue pipe to pass through
the gap surrounding the flue to
the wall. Unfortunately, the depth of the brick alone is not sufficient so he has removed a section of the dpc as well!
course had been compromised. “My condition rating for this defect takes the following path: J—A repair is required, i.e. a new dpc to make good. L—The repairs are not cosmetic/minor issue as the defect (no dpc) will impair performance of this element. N—The defect is serious, and spoils the intended function of the building or services. The defects also affect the structural integrity of the property. P—This path delivers a CR3 rating‖
In addition, Photo 2 shows that the dpc is
It is probable that his selection of a CR3 is
bridged below the back door by the concrete
correct but we need to research the precise
backflow of
addition to the step outside. Unfortunately,
route taken to the condition rating. To do this
gases.‖
John does not tell us what height the dpc is
we must consider, firstly the exact nature of
above ground level. In both cases, a damp
the defect and secondly, the method of
detection meter indicated that there is no
overcoming or repairing the defect.
prevent
rising dampness affecting the building. The question arises as to what Condition Rating is appropriate.
The obvious problem is that the dpc has been removed in part but it has also left the less structural problem that there is a gap around
The bridging can be dismissed as a minor
the flue pipe. The latter creates a health and
defect as the remedial work can be done in a
safety problem because there could easily be a
couple of hours by the average handyman and
backflow of exhaust gases, which will carry
a CR1 would be applicable.
carbon monoxide into the cellar. The second
(A > J > L > M > 1)
feature is the lack of continuity of the dpc.
However, the matter of the boiler flue raises a number of issues and John‘s first thoughts were that this required a CR2 as there was a repair but it was neither serious nor urgent.
Photo 1: Brick removed to fit the flue pipe.
Photo 2: The dpc is bridged below the back door by the concrete addition to the step.
Issue 8 Page 7
HI Technical Bulletin © National Energy Services Ltd 2009
What are the corrective options
the cellar is not occupied but simply used as a
available?
storage area, there is less risk to health and
In order to prevent the backflow of gases, there is an obvious need to seal the gap surrounding the flue. There is also the desire to reinstate the continuity of the dpc. At first thought it might be considered best to insert a piece of slate or plastic to reform the dpc and then to grout the gap around the flue with a standard mortar. This might involve other factors such as the position of the boiler relative to the wall and the floor above and the ease of access to insert the dpc. It might be that another course should be considered. Frequently, a boiler flue will be provided with a flexible collar formed from heat-resistant plastic. The introduction of such a collar will deal with both problems at the same time. The continuity of the dpc is only necessary where there is a vertical continuity in the building. By there being an air gap beneath the dpc, it ceases to be necessary. An alternative might be to consider the use of heat-resistant expandable foam. This has the double effect of sealing the gap around the flue and reinstating the dpc.
Which Condition Rating? So now we have identified the problem and understood it, and we have also identified the methods of repair, we must consider the Condition Rating which should be applied. On its own, the removal of the section of the dpc, leaving a void beneath, does not warrant anything beyond a CR 1 because there is no risk of ground-held moisture being passed through the void. This is a deficiency but, as we have seen, without the dampness, not a defect. (A > J > L > M > 1) Now introduce the boiler and the unsealed flue and we get a totally different view. There is a Health and Safety issue. Therefore, starting at A, there is a potential hazard which requires us to move to B and assess the ‗scale of remedy‘. This (the introduction of a couple of trowels of mortar, a plastic collar or a squirt of expandable foam) must be considered ‗LOW‘, so we move to C where we assess the
the possibility a CR2 can be considered. However, it is the risk to the occupants from carbon monoxide poisoning that is being considered and the potential to affect the living accommodation via an uninhabitable space. In the same way that a similar leak into a utility room could be considered dangerous and therefore a CR3, the scale of risk from this hazard leads away from a CR2. One final consideration is that we are inspecting the property at a fixed point in time and can only report on what we see on the day of inspection. Perhaps the first consideration in assessing the boiler flue should be whether the work, recently undertaken, has been signed off as complete by a registered Gas Safe engineer.
―It is important
The lack of a seal to the room housing the
to consider the
boiler and flue should raise doubts about this, even if the occupier or their representative tells us otherwise. Additionally the flue
interrelationship
terminal is in such a position (less than 2 m
of all elements
above ground level) that it should be provided with a wire mesh cover. We cannot take the
when a potential
heating appliance in these circumstances.
defect is
Even if we are given sight of the Gas Safe
identified.‖
completion certificate we are not necessarily competent to assess if the document is genuine. This is a matter that should be left for a legal advisor to check, and we should identify that this check is required in our report. However, we are undertaking a visual inspection and our limited knowledge of ‗building services that can kill‘ should be sufficient to raise our suspicions and commence us on the path starting at section A and leading to an appropriate condition rating. In summary, this case has identified that several features which are wrong with an element of a property can be easily overlooked because attention was concentrated on whether there was a potential dampness defect. It emphasises the need to understand the relationship between external features and those internally, to consider the holistic inter-
If the room in the cellar is occupied, there is
a potential defect is identified, and of making
the prospect of noxious gases affecting the
use of the Condition Ratings protocol
occupants, therefore the risk is high and the
accordingly, particularly sections A–H.
complications of repair. On the other hand, if
of the fabric
word of a third party as to the safety of a
risk.
CR is 3 without any reference to the costs or
holistic
relationship of all elements of the fabric when
Finally, the case demonstrates the need for reflective thought, as was exercised by John.
Issue 8 Page 8
HI Technical Bulletin © National Energy Services Ltd 2009
Home Condition Survey—An update Do you think it would be possible for every
features are significant in that they also
Home Inspector (HI) able to offer the Home
herald the way for other improvements, such
Condition Survey (HCS) to receive, on
as the possible inclusion of customer reports
average, two instructions a week? A fantasy
from other sources.
and a pipe dream? But why not—how realistic is that dream? Looking at the
What next?
reports lodged with the SAVA Scheme, we
We will be identifying topics for and
can see the following:
commissioning additional fact sheets;
That the total weekly number of HCS instructions has increased by over a third during October. That some of our members are doing an average of one Home Condition Survey a week. We know that there is an untapped market with only about 1 in 5 home buyers
―The weekly
commissioning an independent condition report on the home they want to buy. So
identifying potential partners who might supply additional customer information for home buyers that HIs can incorporate into the report, thus ‗adding value‘; continuing to improve the functionality of the actual reportgenerating software; and evaluating the effectiveness of the marketing support to date and identifying additional tools and services that we can facilitate. In addition to this, we will explore more
number of HCS
why is this not happening already? What is
instructions has
holding everything back?
increased by
Simply, the answer is that, working together,
series of masterclasses were a success. We
we have to create the market. We have to
hope to run more, perhaps focussing on
persuade the solicitor to recommend the
different defect issues.
over a third during October.‖
service, the agent to trust the product and the home buyer to buy the service. Unlike the good old days of the HCR, the work is not
training and/or CPD products to help you build confidence and expertise. The first
We are also considering other opportunities, possibly in partnership with our colleagues at
going to fall into our laps.
the College of Estate Management, and
On 19 October the latest version of the HCS
model.
went live. The two significant features in this version are: The ability to load photographs into the body of the report (rather than just at the end) giving the HI the ability to use a photograph to help describe a feature of the property or justify the condition rating. The ability of selecting fact sheets, which are incorporated as appendices into the final report document (adding value for the end user with no cost and minimal input from the writer). As well as improving the professional look and feel of the final report, these two
building on the hugely successful Fast Track
This is not all one sided. As HI, you have a real responsibility to ensure that your work is of the highest professional standard at all times. Check that your client understands the service they are buying; that you carry out the inspection thoroughly making and keeping detailed notes from the inspection and any desk study that might support your decision making process; and that the report you send to the client has been thoroughly proof read and misspellings or ambiguous statements are corrected. In summary, there is an opportunity here— working together, we can make this happen.
Send feedback to bulletins@nesltd.co.uk; back copies of all bulletins are available in NES one Useful Documents Registration Services: 01908 442 277 registration@nesltd.co.uk Compliance: 01908 442288 compliance@nesltd.co.uk Technical Support Helpdesk: 01908 442105 support@nesltd.co.uk Training enquiries: 01908 442254 training@nesltd.co.uk NES one Credit Top up line: 01908 442299 The content of this technical bulletin is protected by copyright and any unauthorised use, copying, lending or making available of it, howsoever defined, which is not specifically SAVA, The National Energy Centre Davy Avenue, Milton Keynes, MK5 8NA Web: www.sava.org.uk
authorised by National Energy Services Ltd., is strictly prohibited. © 2009 National Energy Services.