As a board member of GPT and GPI for fourteen years, helping to ensure that damp, rot and waterproofing guarantees issued to the public were supported by true insurance rather than manufacturer calamity insurance backed schemes, I also lobbied successfully over many years for PCA members, then BWPDA, to hold Professional Indemnity insurance, only now to find that this requirement for membership was covertly dropped some time ago because too many members complained of the cost.

This is absolute rubbish because in comparison to the turnover of any given company, the cost of Professional Indemnity is peanuts, with the true reason being that too many company owners consistently strip out too much income rather than build up asset value over the years, so as soon as times become difficult, a hard won differential for the members has been dumped because of damaging and foolish short termism, no doubt along with arguements of protecting Member and Association jobs.

I recently provided guidance to a client on the difference between employing members able to offer GPI insurance and others able to offer CGS, which we (in the industry) all know is run by Alf and Shirley who no doubt are quite capable of taking advantage of this thoughless act. My advice was, and bear in mind that when I gave it I was unaware of the covert dropping of the PI requirement, that CGS members do not have to hold PI insurance to issue guarantee backup insurance, which is also via the Kennell Group that own GPI, so if they require best protection they should only go to PCA members because they do carry PI.

So unbeknown to me I  was made to tell a lie, which is not good, however it is the public who will no doubt suffer. 

PCA members have now lost exclusivity and a major differential! 

We believe in the provision of worthwhile guarantees, backed by P.I., you can read about what this means for our clients here

As a company that specialises in waterproofing and building preservation, we make use of a wide range of products, which invariably must include those with a chemical content from bituminous & resin waterproofing systems, to fungicide & insecticide timber treatments.

This creates waste, whether from residual materials, contaminated containers or in some cases where materials simply reach the end of their shelf life. 

Trace COSHH Risk Assessments include guidance detailing how a given product and it’s container should be correctly disposed of, and where ’hazardous’ waste is concerned, this cannot simply be thrown away to end up in land-fill, it must be treated appropriately in accordance with the Controlled Waste Regulations 1992.

So, upon a recent pick-up, I took a few photos:

The waste is sorted, bagged and labelled.

Our waste and the carrier, waiting for their representative to arrive and sort the waste.

Prior to attendance we provide a list of materials to be removed along with the associated MSDS datasheets. The specialist the arrives with pre-produced labelling (visible on the back of the lorry) which is then applied to drums in which the material containers are placed (nothing is decanted), or direct to containers themselves.

Example of a disposal label being applied direct to a container.

Loading the waste.

This service cost Trace £750.00 +VAT and we would hope that other companies in our industry are also disposing of their waste in an appropriate manner (to comply with legislation) so that the playing field is level. 

If you’re employing structural waterproofing or preservation companies, it might be worth checking, or save some time, and give Trace a call?

 Easy as..

Environmental grades (1 to 3) are used to define levels of ‘dryness’, within a given basement or cellar, with a grade 1 environment essentially being more ‘wet’, than a grade 3 environment.

The first thing to understand is that these grades are defined within British Standard 8102 (2009)  Code of practice for protection of below ground structures against water from the ground.  As a ‘code of practice’ the British Standard is the primary waterproofing design guide which we and virtually all others refer to, where considering basements and their construction, and so it makes sense to understand and employ these definitions, which set the benchmark for appropriate waterproofing performance in relation to a given usage.    

Grade 1. 

Basement car park, not fit for purpose, degree of 'seepage' not appropriate.

Example uses of grade 1 environments are listed within BS8102 as ‘Car parking; plant rooms (excluding electrical equipment) and workshops’.  The performance level is defined as: ‘Some seepage and damp areas tolerable, dependent on the intended use, local drainage might be necessary to deal with seepage’.    

In essence, and as per the example above, a basic car park which suffers minimal water seepage may be viewed as acceptable and compliant with grade 1, where the degree of penetration is not detrimental to the intended usage. 

The question is often asked as to how you can quantify ‘some seepage’, and usually the measure is assessing whether a space remains ‘fit for purpose’ with a given level of penetration.      

The same basement car park from another angle, part way through waterproofing works by Trace.

One of the key aspects to understand in respect of ‘grade 1′, is that it is the only grade which allows a degree of water penetration, whereas no water penetration is acceptable with grades 2 & 3.     

If you are considering waterproofing to achieve grade 1, which in my experience most commonly relates to basement car parking, make sure that you consider store rooms, lift lobbies (plus asociated plant rooms) and stairwells, because these will require higher grades and can be costly to remedy.     

Grade 2.

BS 8102 provides examples for grade 2 of ‘Plant rooms and workshops (requiring a drier environment than grade 1)’.  The performance level is defined as: ‘No water penetration acceptable, damp areas tolerable; ventilation might be required’. 

Condensation in a basement store room? Fit for purpose?

You may well ask how damp areas can be tolerable if no water penetration is acceptable?  This relates to airborn water vapour & condensation.  If we take the aforementioned example of a basement car park store room, or a workshop as per the BS8102 example, limited condensation related dampness may not be an issue (as long as generally ‘fit for purpose’, and depending on what it was designed to store), and it may be that the inclusion of ventilation (a mechanism for reducing condensation) as referred to in the standard, is enough to ensure that the space is as dry as it needs to be.       

In such basic spaces, you would not ordinarily consider the inclusion of heating or dehumidification, which can be employed to prevent condensation, and this leads us on to…      

Grade 3. 

This basement suffered no problems of water penetration past the waterproofing system, but was still damp because of poor insulation and insufficient environmental controls

BS 8102 provides examples for grade 3 of ‘Ventilated residential and commercial areas, including ofices, restaurants etc.‘.      

The performance level is defined as: ‘No water penetration acceptable, dehumidification or air-conditioning necessary, appropriate to the intended use’.       

As with grade 2, water penetration is not acceptable but in this case with the inclusion of residential space, this meaning fixtures, fittings, finishes and materials that do not react well with even limited dampness, AND greater vapour production via potential cooking/washing/cleaning/breathing, meaning greater potential condensation; it is necessary within grade 3 to include suitable environmental controls (heating/ventilation/dehumidification) so that  problems of condensation do not occur.  

BS 8102 provides examples for grade 3 of ‘Ventilated residential and commercial areas, including ofices, restaurants etc.‘.      

The performance level is defined as: ‘No water penetration acceptable, dehumidification or air-conditioning necessary, appropriate to the intended use’.       

As with grade 2, water penetration is not acceptable but with the inclusion of residential space in grade 3, this meaning fixtures, fittings, finishes and materials that do not react well with even limited dampness, AND greater vapour production in occupied spaces via cooking/washing/cleaning/breathing, meaning greater potential condensation; it is necessary within grade 3 to include suitable environmental controls (heating/ventilation/dehumidification) so that  problems of condensation do not occur.     

 

Summary.

BS 8102 environmental grades can be condensed into:       

Grade 1: Some seepage acceptable as long as fit for purpose.       

Grade 2: No water penetration whatsoever, condensation/vapour acceptable as long as fit for purpose.       

Grade 3: No water penetration whatsoever, environmental controls necessary to prevent problems of condensation.       

Easy as 1.. 2.. 3..       

Some additional advice:

Examples of usage provided within BS8102, are just that (examples).  The key is identification of usage and ensuring that the environment created by the waterproofing system and environmental controls is appropriate.  For example, if a client is proposing to store textiles, books or delicate valuables which might be sensitive to vapour, and asks you to design appropriately, then while grade 2 might be sufficient for basic storage spaces, you’ll need to provide grade 3 in this circumstance, even if this only means the addition of heating for example.       

Tell clients what they’re getting and use BS8102 environmental grades to explain/confirm it.  Ever heard the story of the retail basement car park designed to grade 1, which then allowed seepage, resulting in the client persuing legally because the ‘waterproofing’ was not working?  In this case the designer had advised in writing that grade 1 was being provided, and thus protected themselves.  All of our designers always advise of the grade provided as a matter of course. 

If you like this post, please click the +1 button at the top of the page, and as always we would recommend taking specialist advice where such considerations are concerned, and would be glad to assist you if so. 

Floating structure - swimming pool.

So I am reasonably sure that you are well aware of this, but do you understand the implications in relation to basements, cellars and waterproofing/tanking systems?

From what we see, many do not appreciate the forces which may be involved, including in some cases those that should certainly know better.  Lets look at an example.

We were asked to inspect a stone built cottage with a cellar beneath which suffered periodic issues of flooding in association with prolonged and heavy rainfall.

The homeowner advised that when sufficiently heavy rainfall occurred, a depression at the end of the garden filled with water to the degree that his children could use an inflatable dinghy and row around.  At the same time, the cellar would fill with water to a depth of approx. 400mm, this giving indication of the degree of saturation in the surrounding ground.

Flooding prevented any real use of the space and so a contractor was sought and found who would remedy the issue.  A specification was put forward and agreed, to install a multi-coat cementitious tanking render to the walls and floor.

This form of waterproofing functions by seeking to totally block water out of the internal space, by providing a physical barrier to water.  Like with any ‘tank’, holes or defects within it will allow passage of water, and so such systems must be perfect or free of any such defect through which water may pass.

The system was installed, the garden filled with water once again, and so did the tanked cellar.

At this point the homeowner called the installer, who returned along with the tanking manufacturer.  A solution was devised and subsequently installed.

The garden filled with water once again, and so did the tanked cellar.

At this point I understand that the installing contractor was no longer trading, and we were contacted with a view to providing advice and an appropriate solution.

Upon attending the property, I asked a various questions including: Was any investigation undertaken to identify the floor construction, before specifying cementitious tanking?  Answer: No I don’t think so.

(Forgive the Jargon) Obvious case of the structure not being strong enough to resist the loads imposed upon it by hydrostatic pressure, resulting in floatation of the floor structure and differential movement & cracking at the wall floor junction, resulting in water penetration….

In simple terms, water filled the ground around the tanked ‘box’ to the degree that the box tries to ‘float’.  In a structure of this type/age, where a minimal depth floor construction likely exists, spanning in-between the retaining walls; the floor represents the weakest element, and when water pressures upward upon it, the floor may move, typically causing cracking at the wall/floor junction, and failure in the tanking.

When I inspected, this is what I could see:

Flexible tanking applied at wall/floor junction.

A flexible tanking product had been applied to the wall floor junction in areas, localised patch repairs had been undertaken to cracking in the floor at the door threshold, and a sump pump was included in one corner of the cellar space.

Evidently, the problem of differential movement and cracking had been identified, with a flexible product being included to address this, albeit unsuccessfully.  The inclusion of a sump pump in a solid chamber (so would not de-water beneath the structure) had no tangible benefit as only accepted water once penetrating past the tanking.

The problem was addressed by installing a maintainable drainage channel system at the wall floor junction, in a concrete chase, linked to a triple pump sump pump system in a solid liner.  This design still makes use of the existing tanking barriers to the walls and floor, however relieves the pressure by collecting groundwater, this solving the problem.

But, my point is that one should consider the nature of the structure and the relationship between it and any proposed waterproofing system.  In this case, they clearly did not consider this appropriately.

Lets look at some other cases where the forces of hydrostatic pressure have come in to play:

This one (supplied by Triton http://www.triton-chemicals.co.uk/) shows an adhesive bitumen sheet membrane tanking system applied to the internal face of a retaining wall, with a block wall constructed in front of it.  This could not be tied back as this would obviously puncture the tanking, and when water pressured, causing the bitumen membrane to bow inwards, it pushed over the inner leaf:

Inner block wall pushed over by hydrostatic pressure.

This is a photo from a project which suffered the same issue, showing water causing the tanking to bow in:

Bitumen sheet membrane 'bows' in with hydrostatic pressure.

This is the same project with a before/after shot, note that the inner block leaf was taken down where exposed visible because of health & safety concerns:

Bitumen tanking pushes over inner leaf (left), after installation of Trace system (right).

Finally, the extent of flooding present within this basement caused the insulation and screed (containing under-floor heating) over to float!

Screed laid on insulation floats as a result of flooding.

In closing, consider the nature of the structure, or call Trace and we will consider this and all other appropriate factors on your behalf.

This is the story of an unfortunate homeowner let down by a poor waterproofing design, and an installing contractor that ceased trading, leaving substantial problems and costs in their wake. 

When we build below ground, we have to include waterproofing or otherwise accept the risk that groundwater will pressure on the structure and penetrate, which in most cases is not what we want in our basements & cellars.  

Broadly speaking we can address this risk in one of two ways, either by forming a barrier to block water out, or accept that some water will penetrate and ‘deal’ with that which does. ‘Dealing’ with or ’managing’ water, is much of what we do, because if you remove it, it ceases to be a problem. This form of waterproofing construction is known as ‘drained protection’, and the systems typically comprise three elements:  

1. A sump pump system, to remove water collected within the drainage system.
2. A drainage channel system, installed to collect penetrating water and to act as a conduit to allow water to flow to the pump.
3. A cavity drainage membrane, which is applied over all ground retaining wall and floor surfaces, so that any moisture or dampness present, is isolated from the interal space.

Thus, by removing all water, and isolating all dampness from the interior, a dry space can be provided.  

A typical section detail might look something like this: 

Drainage channel in chase (in green), dimpled cavity membrane to walls and floor.

Each of the components has a role to play, but in particular the drainage channel is key, for a couple of reasons.  Firstly if you include it at the wall floor junction where most water penetrates, you can catch water at the point of penetration, and secondly we can include access ports which allow the channels to be maintained i.e. cleaned out, which we do with each of our systems at least annually.  

Maintenance is super important because it allows us to ensure that systems keep working, which means dry basements, happy clients and pride in the job.  Hence we always include drainage channels as standard within our designs.  

However, it is also possible to construct drainage waterproofing systems without using the channels, because cavity drainage membranes have their own drainage space created by the dimpled structure of the membrane.   

Dimples create a drainage space beneath the membrane.

Some technical documentation for these products provides figures for the quantity of water which can flow behind or below a given membrane, and while this can in theory be useful if anticipating water flowing down a wall (although if this much is penetrating there are other questions to ask), when it comes to water flowing across a floor beneath a membrane, this is not necessarily desirable in our opinion.  

Why?  Well, how do you reliably clean out and maintain the drainage space beneath a floor membrane?  What happens if the drainage space clogs in time?  

Well, a couple of years ago I was asked to view a property which had been underpinned, this creating a large rectangular basement employed as habitable living space.  The basement remained dry for approx 2.5 years before water started penetrating through the floor construction at the perimeter, and we were subsequently asked to investigate.  

So, my first question: Where are the inspection ports?  

Water penetration at wall floor joint (note the nail).

Homeowner: What do you mean, inspection ports? 

Me: Inspection ports for the drainage channels.  

Homeowner: What do you mean, drainage channels?

 

So, we lifted a small section of screed at the wall floor junction, cut through the 8mm stud profile cavity drainage DPM, and sure enough, no drainage channels.

 

 

We then removed the access hatch from above the sump system at the opposite end of this rectangular basement, and this is what we could see:

 So, we could clearly see that the drainage space beneath the membrane was clogged, which in time effectively stemmed the flow of water to the sump, which subsequently pressured on the membrane (which is not designed to hold back water under pressure) and came through. 

The material which clogged the membrane is free lime & mineral salts, leached from the new concrete by water moving over and through it.  The liklihood is that water penetrates through the concrete underpinning/dry-pack, runs down the retaining wall, then fully across the floor slab, picking up salts as it goes, this eventually causing blockage and failure of the waterproofing. 

These days, you can spray treat the concrete or include additives to limit this, although spray producrs are certainly not 100% effective and a degree of lime will still be leached, this reducing in time, being most severe in the early life of the structure. 

So, what was the error?  The fact is that the system was not designed to be maintainable. 

What should they have done?  They should have included drainage channels with inspection ports.  

The channels would have collected water at the wall floor junction, this preventing it from spilling fully across the floor slab, reducing the extent of concrete which water could access and leach lime from, and ports + maintenance would have ensured that the channels never blocked, this preventing water from pressuring on the membrane, resulting in a permanntly dry basement.  The aforementioned treatments would also have reduced the extent of lime. 

So, I presented the homeowner with a report including a not insubstantial quotation for taking up the floor construction and forming a more robust system, also commenting on the lack of compliance with the advice included in the ‘code of practice’, British Standard 8102 (the waterproofing guru’s handbook).  This was forwarded to the installing specialist contractor who no longer traded (!) but could be contacted, who basically argued that it was an ‘approved design’, and that I was commercially biased. 

The sad fact is, if you look for them, you can still find ’standard details’ online for ‘membranes only’ drainage waterproofing systems, which are not maintainable and would fail in similar circumstances. 

While this was certainly a ‘perfect storm’ type scenario which caused failure in a short space of time, I would still not be surprised to see more of this problem in future where such designs are employed. 

Ulimately it’s a cheaper method and a company may win more work bidding to install such systems, but as a company which issues long term guarantees, we just would not ever consider it… 

Hygroscopic Ammonia Salt Contamination In Converted Barn

A common problem when barns are converted relates to failing to take account of the latent contamination by animal urine, i.e. cows for instance will spray up to at least 1.5 metre high when relieving themselves, this leaving the substrates full of ammonia salts that are hygroscopic and extremely aggressive to ANY direct applied plaster.

The photo here shows a wall that had originally been covered in dabbed plasterboard when conversion occured, this subsequently failing and then  plastered again with a cementitious based tanking system, including waterproofing additives. As you can see, that failed as well, calling for a third plaster system to be applied!
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 A Glossop Chartered Surveyor has recorded the top industry grade in professional exams organised by a building preservation trade body – for the second year running. 

 David Hockey, 31, secured the Student of the Year title in the Property Care Association’s surveying qualification, the Certificated Surveyor In Structural Waterproofing (CSSW).
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Just posted a new article concerning guidance within the updated British Standard for Structural Waterproofing 8102:2009 Code of practice for protection of below ground structures against water from the ground.

The standard advises that a waterproofing specialist should be included on the design team, but the process may fall down where said specialists disclaim design responsibility, putting this back onto the very Specifiers they’re advising. See link below for the article:

http://www.tracebasementsystems.co.uk/bs8102-design-team.php

David Hockey, BSc. (Hons), MRICS, CSRT, CSSW of Trace after recieving the CSSW award, with Brian Davison of Delta Membranes

David Hockey of Trace receives the PCA 2010 award for highest CSSW examination marks in the year, this after winning the 2009 award for CSRT, which brother James had also won in 2008.