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INDUSTRY INSIGHTS | Q&A with Delta Membranes

An imperative part of any Knowles project is ensuring our waterproofing and drainage is exceptional, which is why we used DELTA. We sat down with David Symes, Delta’s Managing Director, who oversees key accounts, including Knowles, as well as Delta’s educational and training programmes.

David’s experience spans products and solutions incorporating structural waterproofing, damp proofing, flood resilience and ground gas protection systems.  His expertise encompasses both commercial and residential projects.

Tell us a bit about yourself?

I joined Delta’s board of Directors in 2012, before taking on the Managing Director role in 2020.  I entered the Construction Industry after leaving School, initially as a Damp Proofing and Timber Treatment Technician working with a small family concern in Northampton where I served my apprenticeship while attending College on a day release basis to study Carpentry and Joinery at Nene College.

From here I moved into Surveying for a National Company serving 20 years in this role to Senior Surveyor.

I was delighted to join the Delta Team and work alongside Delta’s then co-founders Chris and Brian where I acquired new skills, and the rest they say, is history.

I’m a Waterproofing Design Specialist and can be found on the WDS Register, hold CSSW qualification and the equivalent of a HNC in construction. 

Tell us a bit about the history of Delta Membranes?

Delta Membrane Systems Limited provides a full range of waterproofing and damp proofing solutions for architects, specifiers, developers, contractors and homeowners on new, retrofit and refurbishment construction and in flood resilience.  We also supply ground gas protection membranes protecting structures from harmful ground gases such as radon, carbon dioxide, methane and hydrocarbons.

We are proudly the Leading manufacturer of Type C Cavity Drainage Systems in the United Kingdom.  We eat, sleep and breathe waterproofing solutions.  We represent Quality Products, Solutions and Innovative Design.

We have a passionate team of professionals from a mixed and diverse background of disciplines, but we share the same goal and that is to develop sustainable long-term solutions in the sector.

Delta HQ can be found in Epping Essex, with smaller regional bases covering the whole of the UK, Scotland and Wales.

Delta is successfully lead by its Directors, David J Symes, Kevin Dodds, Christopher Burbridge and Brian Davison.  With Kevin overseeing the operational, structured business development and personnel development and myself running the technical side of the business. 

What makes your products different to those on the market?

This is a great question.  Being incredibly biased we truly have some awesome products which are unparalleled. 

Research and Development is incredibly important to us, we’re constantly looking at ways we can develop, design and enhance our products, services, techniques and processes. 

Perhaps what makes Delta stand out in the market is we believe in offering value to our customers, we don’t just make a sale, we build relationships.  The structural waterproofing industry is a very niche sector and a competitive market, we have an outstanding reputation for our Technical Team’s hands-on approach and knowledge which is backed by an equally impressive sale’s office.  

Employee Development is deeply ingrained into our culture. It is not seen as a box to be ticked, or something to be done, instead, training, coaching and development activities are seen as continuous. 

How long have you worked with Knowles?

We’ve been working alongside Knowles for over 10 years.  During those years, I’ve discovered that one my favourite things is learning about Knowles and their values.  Whether they are working on a small project to a large commercial project, they always provide a personalised service that exceeds expectations. 

For anyone working in the structural waterproofing industry we are all amply aware that each project will have its own set of challenges because each project is unique.

Improving the collaboration from manufacturers to main contractors and sub contractors throughout the supply chain is a key element for project success.  The success of the collaboration on a project depends on communication.  Good communication can correct plan and specification flaws and reduce delays, we luckily have a great line of communication between the two companies, from planning to site meetings, it’s always a pleasure with Knowles’ teams.

What has been your favourite project to work with Knowles on?

Yet another great question.  It’s a bit like choosing your most loved child, I am not sure I could name one favourite project.  The great and wondrous aspect of Structural Waterproofing is no one project is the same and no one day is the same.  One of the most interesting projects I have had the pleasure of working on with Knowles, has been a development in Oxfordshire.  I have found this project incredibly rewarding because of the challenges raised and it’s certainly introduced me to new skills and approaches along with opportunities for creative thinking which has been exhilarating to overcome.  It’s always a real joy to be able to see a project take shape from concept to finish.  This project provided a great opportunity for teamwork. 

When you create an open and transparent way of working, the whole process becomes so much more enjoyable.

Thank you to the Knowles team for the opportunity to work on the project. It has certainly been an enjoyable project that has provided both challenges and rewards.

Aside from the Oxfordshire development, some of the structural waterproofing projects that I find most fascinating are the historic ones, the upgrading old to new and knowing that we are preserving structures for future generations to enjoy.   

Why should clients or professional teams feel confident when using Delta?

What defines Delta is our approach.  We specialise in solutions, from the smallest domestic project to high-end residential developments, commercial structures and civil projects which can be tailored to even the most challenging environment – above or below ground.  We consider the entire project process from concept to completion to the very finest of detail and can provide solutions for all project requirements.

We encourage best practice.  Our step-by-step guidance on diagnosis, prognosis, treatment and preservation is updated daily using the robust evidence-based methodology, legislation and expert opinion. 

We strongly believe that knowledge is power, therefore, we have developed a culture whereby best practices are identified and shared across all departments and we are committed to offering training and educational programmes to develop skills and knowledge within the sector and continually promote standards. 

Keeping our customers’ trust and loyalty is particularly important to us and we strive to deliver a service that meets and excels expectations. 

For Delta, sustainable development means adopting business strategies and activities that meet the needs of our customers today while protecting, sustaining and enhancing the manufacturing process of the future.


How does Delta keep up with the latest technologies and innovations when it comes to your sector?

Both myself and my fellow Directors are on various committees, with Kevin being at the forefront of developments within the Sector having been a valid committee member of the BSI BS8102 Review Committee 2009, BSI8102 Review Committee 2020/21 and the NHBC Task Group for the New Standards of Waterproofing of Basements and Other Below Ground Structures.  Kevin continues his roles as Chairman of the Basement Information Centre, Technical Committee, Chairman of the PCA Structural Waterproofing Group Steering Committee and us all sitting as examiners for the CSSW qualification.

We are committed to our role in facilitating the transition to a more sustainable, low carbon, resource-efficient manufacturing process.  By creating products that offer long term performance and protection for the lifespan of the structure, we can reduce the whole life costs and reduce the carbon footprint over the whole life of the structure.

The pace of change in the sector seems to accelerate at an ever-increasing rate, it’s a genuinely exciting era for structural waterproofing and really does provide me with the opportunity of doing something that I really love.

INDUSTRY INSIGHTS | Q&A with Architects, The Basement Design Studio

Basements provide an exciting opportunity to add more space to homes, but they must be carefully thought out to ensure the layout is efficient, and that natural lighting has been considered. Knowles have worked on many projects with Mike Wiseman from the Basement Design Studio, so we wanted to speak to Mike to understand how his practice works and what clients should consider when planning a basement.


Tell us a bit about you and the practice?

The Basement Design Studio was established in 2010, along with Paul Schaaf and as the name suggests, we primarily design basements! My background was always in private practice architecture having spent most of my younger years (1980 onwards) at one of the country’s oldest established practices, founded in 1856 and based in Windsor. The recession of 1990 and reduction to a 3-day week (yes, that really did happen in the old days) prompted me to set up my own practice. A chance meeting on a golf course in 1995 with Robin Knowles then steered the rest of my career to where we are now. Robin was then just setting up The London Basement Company and somehow, I ended up being the ‘design’ part of what was undoubtedly the very start of the ‘design and build’ basement revolution. I think it’s fair to say we both had to learn fast and arguably went on to develop many of the construction techniques and waterproofing details now considered ‘normal’ in the basement industry.


How do you first approach schemes that may be limited for space?

Basements are not always the huge, multi-level ‘icebergs’ that the press seems to love. In fact, the very early basements were driven by the desire to simply gain some extra space from unused cellars. Use of the space is therefore important and, given the cost of basements, I will always try and get the additional space that a client wants, in the minimum area we can. Remember, it’s not just the space gained at basement level, but also how that frees up the other areas in the house. As an example, some of the simplest basements, containing just a kid’s playroom and utility area, can mean the clients kitchen is no longer full of laundry and the living room no longer full of kid’s toys…suddenly, they can live a normal, civilised life, have guests round to dinner again and sit in comfort.


What is your favourite trick to maximise natural lighting for basements?

One of the most common responses I hear when people see examples of basement projects is ‘it doesn’t look like a basement!’. We would always try and make the basement feel like it is part of the original house and that the space is every bit as good as the above ground rooms. That is largely due to being able to introduce the feeling of natural light and, just as importantly, natural ventilation into the basement. Clearly, a basement is never going to have the ‘view’ that an above ground room can have but just the introduction of a well-designed light well and properly proportioned window can have a massive impact on the feel within a room. The amount of light that even a small lightwell can provide never ceases to amaze.


What has been your favourite project to work with Knowles on?

Knowles have undertaken some quite staggering projects over the last few years, some of which I think I’m glad NOT to have been involved in, sleepless nights et al. We do currently have a couple of nice projects together, both on Listed properties funnily enough; one 2,800 sq ft project under a house in St John’s Wood, the other a 2,250 sq ft basement under the garden of a house in the Buckinghamshire countryside. My favourite?… That has to be the secret underground garage, fully air-conditioned for 70 cars in a private collection!


What can clients expect from the Basement Design Studio?

Since 1996, we have probably designed and submitted over 2000 planning applications across most of the London Boroughs, so there isn’t much we haven’t seen. We don’t profess to design the largest, the wildest, or the most original basements in the world, but we do like to think we design sensible, practical, and usable basements for all our clients.

Capturing Construction Sites | Q&A with Alex Harvey-Brown, Knowles’ Photographer and Videographer

Capturing construction sites is a fine art, and one that has many benefits. At Knowles, we have always invested in photography and videography, of which is used across our social media channels, in project case studies, but also as a means of updating clients. We are regularly praised on the level of our site photography, and it is all down to Alex from Savannah Photographic, of whom Knowles have worked with for over 6 years.

We wanted to talk to Alex about his tips on capturing construction sites, and what he looks for on Knowles projects.

What do you look for when photographing a project?

The first thing I always look for are the angles and lines that form patterns – there is always some interesting geometry to look out for. Then I’m always looking for the operatives doing something interesting and action packed!

What is difficult/ what issues do you face when photographing a construction site?

The day to day working of a building site is not always geared to a photoshoot! There is a lot of noise and machinery to be aware of, so I have to be careful of where I go when I’m trying to get the perfect angle! Luckily for me Knowles sites are always very safe and well organised!

What lense/ camera settings do you use and why?

I’m always keen to capture the scale of Knowles sites so I like to use an ultra wide angle lens for most of my work. Some sites, especially basements, don’t get much sunlight so I have to use long exposures and slow shutter speeds to get as much light as possible into the camera.

How do you compose a shot? And what makes a good shot on a construction site?

As I mentioned the geometry of a site is always the first basis for my compositions, there are always interesting lines and angles. From steel beams to concrete walls, there is a lot of beauty in the architectural shapes of a Knowles site. If I’m shooting an operative at work I always try to get the site context in the background. Sometimes dust from works can catch the light in beautiful ways too!

How do you video a project?

I approach filming sites in a very similar way to photographing them, however with moving pictures I have some cool tricks I can use to capture the scale and scope of Knowles projects. Techniques like time-lapses and slow motion and using tools like gimbals and drones to get a perspective you wouldn’t normally see from the ground.

Can you name some of your favourite projects that you have photographed for Knowles and explain why they stand out?

Some of my favourite projects are probably the stately homes in the country as they are always in such beautiful surroundings and I have lots of fun trying to find the best way of capturing the scale of what goes on and shooting all of the myriad skills and building techniques on those very complex sites. I also love the Kensington High Street project, it’s fascinating having a site right above a tube line 

(I’ll confess to being a bit of a train geek!), and the original buildings being really old. So much heritage and history and right in the heart of London – it’s really special. There are loads of things going on with the project as it is very complex, so I really enjoy the challenge of trying to capture all the elements as they happen.

Savannah Photographic

Savannah Photographic

Photography and Films by Alex Harvey-Brown

The Importance of Joinery in the Classical House

An extract essay on “The importance of Joinery in the Classical House” written by Knowles Group Director Aidan Mortimer, taken from “The Art of Classical Details: Theory, Design and Craftsmanship” first published in 2013 by Phillip James Dodd (

This essay explores the historic importance of joinery in houses built in the eighteenth century in Britain and America.

The Importance of Joinery in The Classical House

– Aidan Mortimer, MSc in Historic Conservation FCIOB FRSA FRICS
The classical style seems to be as popular as ever in both Britain and America; indeed its appeal is universal with classically inspired mansions presently under construction in every corner of the globe, from Beijing to Moscow and Kuwait to the Bahamas. They all share a common heritage with their roots deep in 18th-century Georgian Britain, which is widely acknowledged as the high watermark of Classical architecture

A classically-trained craftsman applying the finishing wax to a Doric entablature crafted in English Oak.

To understand the role of joinery, or millwork as it is often referred to in America, in the Classical house of today, it is well worth exploring the historical development of the 18th-century house and the importance of joinery in houses of this period.

In Britain, the catchall term “Georgian” broadly covers the period from 1714, the date George I came to the throne, through to 1830 when George IV died. Of course, the style is not specifically tied to the reigns of these monarchs and its origins in Britain lie a century earlier in the works of, amongst others, Inigo Jones, and after 1830 the style continued to refine and develop in all sorts of interesting ways throughout the 19th century.

Georgian style can be broadly broken down into three stylistic periods: Palladian (c1714-60), Adam or neo-Classical (c1760-90) and Regency (c1790-1830). In America, the Colonial style echoed the first two periods and the later Federal style broadly mirrored the Regency style. In many ways the 18th century American house was markedly similar to its British counterpart, although ideas sometimes took a while to reach those provinces distant from Britain.

The materials out of which British and American houses were built during this period did, however, differ. Wood was, for example, far more widely used on the east coast of America than stone, which was rarely found locally. By contrast, in Britain there was a wealth of easily sourced building material from sandstone and slate in the north of the country to limestone, flint, and locally fired clay bricks and tiles in the south. As a result, many of the most significant country houses were, where their owners could afford to flaunt their wealth, built in stone and most of the external ornament on these buildings was also in stone. On the east coast of America houses of the same period were almost entirely constructed in timber, with wood sidings on timber framed walls under shingled roofs and with porticos, colonnades, and ornate doorcases all made from wood.

Despite these differences in construction across the Atlantic, buildings did, and still do, share many common millwork details, most notably windows, doors, panelling, and staircases. Windows are usually the first element of a Classical house you notice; they give a facade balance and create a rhythm. The window synonymous with the Georgian era is the double hung sash, which was adopted almost universally in Britain and America, and also Holland, although its use did not spread much further. Windows of the Palladian and early Colonial period were rarely made to standard sizes or pane dimensions but were characteristically six over six or eight over eight panes. As the 18th century progressed glazing gradually increased in size and four over four and even two over two panes became commonplace.

Window frames in Britain were generally hidden behind stone or brick reveals, leaving little margin of the frame to be seen externally. This was to protect vulnerable wood from fire, which periodically ravaged parts of the rapidly growing cities. Glass, clearly a key component of any window, was predominantly “crown glass”, the name derived from the manufacturing process which involved spinning out a globe of blown glass to form a disc which was then cooled on a bed of sand. Panes cut from this could generally not economically be more than 10 x 15 inches. For most of the century America relied on crown glass imported from Britain and it was not until 1787 that the first American window glass factory was set up in Boston. By 1830 glass-making had become very much more refined and 1832 saw the first plate glass produced. This revolutionized glass-making with dramatically larger panes, which in turn had a profound impact on window making. The substantial glazing bars with “ovolo” mouldings needed to support small panes of vulnerable glass were no longer needed and were gradually replaced by slender mouldings, such as the popular “lambs tongue”. Windows of the Regency period had significantly fewer glazing bars and by the 1840s sash windows could be made with no glazing bars at all. As areas of window glass grew so too did the size of windows, which often extended down to the ground to give access to the garden or, at first floor level, verandas. 

The Regency period also saw narrow panes introduced to the borders of window glazing, often with coloured glass; the architect Sir John Soane delighted in using amber-coloured glass at every opportunity.

Whilst windows give balance to the facade of a building, doors are the focal point and the 18th century saw the creation of the panelled door: prior to this most doors were of wide planks on heavy framing. Early Georgian doors were often six panelled with simple bold mouldings, although by the Regency period the number of panels had reduced to four or two with subtle mouldings and elaborate door furniture. External doors were invariably emphasized by a surrounding doorcase. Again designs became more refined as the 18th century progressed: heavy hoods common early in the Georgian period gave way to simple pilasters supporting a pediment or lintel.

Designed by Robert Franklin the library at Hanwell Castle is of English Oak with hand-carved corbels.

If externally millwork served to reinforce Classical proportion then internally millwork gave owners the opportunity to show off their taste and sophistication and, of course, their wealth. Newly discovered exotic hardwoods could be used to make doors, libraries, and staircases and the finest wood carvers could be employed to create ornately detailed fireplaces and doorcases. The most impressive millwork was unsurprisingly to be found in the principal reception rooms and in chosen rooms on the bedroom floors of a newly constructed early Georgian house. The entrance hall and rooms running off the hall where guests were received and entertained were often panelled to their full height up to a cornice or crown mould. Millwork was generally robustly detailed with deep three-dimensional mouldings such as the popular “egg and dart”. Much of the panelling was in painted pine with occasional rooms, in Britain, in locally sourced oak. Doors to rooms on the principal floors in larger houses were invariably six panelled and of hardwood, wax polished to show off beautiful timbers and fine craftsmanship to best effect. The refinement of the Classical style with a movement towards finer, lighter details as the century progressed, was seen in the architectural detailing of joinery inside the house. By the 1760s the practice of full-height wood panelling was giving way to simply detailed wainscot, referred to as dado in England, panelling at low level with flat plaster on the walls above and, eventually, the restraint of the Regency period saw plastered walls with only simply moulded shallow profiled wainscot rails.

Whilst the role of joinery in ornamenting the Georgian house gradually diminished through the 18th century, staircases remained the most impressive feature of any well-to-do house throughout the period; here the millworker had a real chance to shine. Early Georgian staircases were robustly detailed with handsome turned balusters and heavy handrails, often constructed entirely from oak or even West Indian mahogany. Lesser homes used cheaper pine, but invariably still had hardwood handrails. The most impressive early Georgian staircases had open strings (where the ends of the treads are left showing), which were beautifully carved. Each tread would then typically have three balusters emulating columns sitting on urns separated by squared blocks. As the century progressed, balusters became more slender and sometimes twisted. These magnificent structures, befitting their importance, were well lit by windows and, later, skylights. In the last decades of the 18th-century turned balusters were distinctly out of fashion and were replaced by thin “stick” balusters and by 1800 wrought iron increasingly took their place; the “age of wood” was coming to a close.

Designed by David Easton, this library includes a bespoke mantlepiece, wall panelling, bookcases and fluted Ionic columns.

The Georgian period was a remarkable one, with building work on a scale not seen before, and those working in stone, brick, plaster, and especially wood dramatically developed and refined their craft.* Remarkably, the craft skills that created these buildings largely survive today in both Britain and America. The growth of the conservation movement over the last 30 years, coupled with a revived interest in constructing new buildings, particularly those in the Classical style, using traditional craft methods and correct historical detail have created a strong demand for craftsmanship. 

With enlightened patrons commissioning extraordinary work and architects and designers producing both scholarly and innovative design incorporating high craft, long may these skills flourish!

*For further detailed information on the Georgian period I thoroughly recommend The Georgian House in Britain and America by Steven Parissien, from which many of the key facts in this essay have been drawn.

Sustainable Living

What you can do to your home to keep it as sustainable as possible, without sacrificing style and aesthetic.

What is sustainability within the home and why is it important?

A sustainable home is a home that is built or retrofitted to run efficiently, respects resources, optimizes energy and water usage and uses quality systems with longevity in mind. Sustainable homes use low-impact, high-performance materials, are efficient in terms of manufacturing, shipping, and installing and by using high-quality materials and systems that break less and last longer, they therefore waste less.

By making your home more sustainable, you are contributing to improving the environment. But that is not all. A sustainable home can lower running costs, save energy, water, and maintenance, create a healthier environment for your family, and still look good at the same time.

Knowles regularly look at ways to make the build of a home sustainable, not only during the construction process, but for the long terms too. Most of Knowles’ projects feature sustainable elements such as Ground Source Heat Pumps and High-Performance Windows, as these provide beneficial features that clients want to see!

Ways you can make your home more sustainable:

Use reclaimed wood and brick

Materials such as wood and brick can be salvaged from the remains of old buildings, and then carefully restored and upcycled. Not only is this a great way to keep your project as green as possible but from an aesthetic perspective, reclaimed wood flooring or a reclaimed brick wall can have character and charm, whilst also creating a cost environment, particularly apt for country living.


Passive solar design

Passive Solar Design uses energy from sunlight to aid in heating and cooling your home without using mechanical or electrical equipment. It relies on building materials that absorb, reflect, or transmit the sun’s radiation, whilst inside spaces are designed to facilitate the movement of sun heated air without the use of fans. This can reduce the amount of energy used to heat and cool your home.


High performance windows

Windows account for at least 50% of lost energy. Technologies including double glazing, special coatings, nonconductive framing materials and higher-quality, air-tight construction all result in better energy efficiency.

Steel windows and doors not only look stunning but also provide incredible energy efficiency. The key is to get thermally broken profiles. “Thermally broken profiles use resin isolators inside the steel profile to reduce heat transfer in harsh climates. This innovation is an important factor in steel’s returning popularity,” explains Joy Palmer of FireRock. “Thermally broken profiles also prevent interior condensation in colder weather.”



Good insulation is key in your home energy efficiency. Older homes might need improvements such as foam injections or blown-in attic insulation o to improve insulation of walls, floors, and ceilings, improving the overall efficiency and insulation of the home.



After HVAC systems, appliances are the real energy consumers in your home. When you buy the most energy-efficient options, you dramatically cut the cost of operating. The appliances that tend to consume the most electricity include, refrigerators, dishwashers, ovens, air conditioners, clothes dryers, and water heaters. Investing in stainless-steel Energy Star label appliances not only look sleek, but they also guarantee significant energy savings.



Replace fluorescent light bulbs with LED or CFL bulbs which offer longer life, greater energy efficiency and fewer toxic metals.


Smart technology

Technology such as smart thermostats and hybrid heat pumps use less oil and gas and make it easier to track and reduce how much energy you use, and in the long-term you will feel the effect on your monthly bills.


Non-toxic paint

Eco or non-toxic paints emit fewer toxins to reduce indoor air pollution. They are also less toxic to manufacture, so good all round!


Ground Source Heat Pump

Ground source heat pumps (GSHPs) use pipes that are buried in the garden to extract heat from the ground. This heat can then be used to heat radiators, underfloor or warm air heating systems and hot water in your home. Benefits include lower fuel bills, reduction in your household’s carbon footprint and the ability to heat your home as well as your water! Most new projects by Knowles now feature GSHP’s!

Lockdown Living and How Knowles Can Help!

Lockdown has made it clear what extra space we need in our homes. So when struggling with ways in which you can maximise space in your home, have you considered a basement?

Considerations when planning a garden basement

Adding a London basement underneath a garden is an innovative, space-saving solution when building up isn’t an option. If the footprint of your house isn’t big enough, extending the construction works into the garden can have many benefits.

Typical Timelines for London Basement Construction Projects

The most common question from Knowles basement clients in London is ‘how long will it take?’. There is no simple answer as each basement conversion project is unique.

How to Repair Foundations with Underpinning

Whether increasing the depth of a building’s foundations or repairing faulty or damaged foundations, underpinning is an important part of basement construction to enhance stability and strength. Various methods of underpinning which can be chosen depending on what is best for the property.

Q&A | Aidan Mortimer, Group Director

I have always had a keen interest in building and architecture and having studied construction at Oxford Polytechnic in the late 1970s I set up and ran my own building business in the 1980s restoring and altering traditional buildings in Oxfordshire.