Avant Garde Damp Solutions

We find where the damp is really coming from before we treat it, across North and West London since 2003.

Damp proofing, wet and dry rot, woodworm and basement waterproofing for homes, commercial and historic buildings across London and the Home Counties, from a deliberately small company with two teams.

Call free on 0808 164 8398Email us

Est. 2003PCA qualified surveyorsWhich? Trusted Trader

A bay-window room freshly re-plastered, with a parquet floor

Freshly re-plastered, one of our recent jobs.

Our ratings

Google

4.9out of 5

from 35 reviews

Google reviews

Checkatrade

9.88out of 10

from 284 reviews

Member since March 2008

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Which? Trusted Traders

4.9out of 5

from 95 reviews

Hertfordshire Trading Standards Approved

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Damp Surveys come first, and they’re impartial

If you suspect that the property you own or live in is suffering from damp, our fully qualified surveyors can help. We carry out thorough inspections of properties throughout North and West London, including Ealing and Hampstead.

“Our business ethos is to offer impartial advice that is not driven by a sales target, therefore we have chosen to charge a small call out fee for our visits. This covers our time and petrol and allows us to remain unbiased in our reporting.”

Rising damp has been widely misdiagnosed in buildings over the last 30 years. A highly successful sales campaign by damp proofing companies offering “FREE Damp Surveys” has convinced many people that a new injected chemical damp proof course is nearly always required. We would rather find the real cause, with minimal disruption to the rest of your premises.

Common symptoms of damp to look out for

  • Mould on walls and furniture / damp or wet patches on the walls
  • Rotting window frames, skirting boards or floorboards
  • Wallpaper peeling from the walls / paint flaking from the walls
  • Stains or tidemarks on walls / flaky or bubbling plaster
  • White powder or crystal-like particles on wall surfaces
  • Crumbling mortar between bricks or stonework on the exterior of the building
  • Rusting steel and iron fasteners
Arrange a damp & timber survey
Taking moisture readings on a bedroom wall with a yellow-cased meter

PCA trained and qualified surveyors

We use a PCA (Property Care Association) trained and qualified surveyor to carry out inspections, offering you peace of mind that a duty of care is being observed while also remaining within their recommended guidelines.

What we treat, layer by layer

We believe that getting to the root of the problem is paramount for treatment. Each house is different and therefore requires a bespoke solution.

  • Damp Proofing
  • Woodworm
  • Damp Surveys
  • Wet and Dry Rot
  • Basement Waterproofing
  • Commercial Damp Proofing
  • Rising Damp
  • Concrete Repairs and Treatment
  • Structural Waterproofing (including basement conversions)

Finish plaster

Damp Proofing

If our expert surveyors detect damp at your premises, whether that’s damp walls or penetrating damp in your house, there are often a range of issues that can be causing it, and we believe getting to the root of the problem is paramount.

We believe that damp proofing using chemical injection should only be considered as a very last resort.

Instead, we prefer to take a holistic view of a property, applying our extensive knowledge of traditional construction in order to find the true source of the moisture. Our damp proofing process can also include:

  • Wooden skirting boards may need replacing due to decay from wet rot
  • Walls will generally need to be re-plastered with sand cement render to hold back the residual moisture and salts
  • Treated walls are replastered to full height resulting in a superior finish

Render

Rising Damp

Rising damp can be a major problem in older houses where a damp course has not been applied, or where previous damp treatments have been breached or failed. If left unaddressed, it can compromise the structural integrity of your property, as well as your health.

Signs of rising damp include

  • Walls that are moist to touch
  • Tide marks
  • Peeling wallpaper
  • A salt-like substance appearing on the walls

How we can treat it

  • Injection of a chemical damp course
  • Re-plastering of salt-affected plaster
  • Additional external treatments may also be required

Timber

Wet Rot & Dry Rot Treatment

As the two most common forms of fungal decay, if left unaddressed wet and dry rot can escalate into major structural damage. A damp survey is a crucial part of dealing with the problem, and it lets us establish what treatment is required.

Wet Rot

Wet rot appears as a black fungus on timbers in contact with wet or damp masonry, causing the timber to become soft and spongy to touch and discoloured. We remove the source of dampness, replace the decayed timbers and, if necessary, install a physical barrier to prevent further damage.

Dry Rot

Dry rot is the most serious form of fungal decay in buildings, spreading through both timber and masonry to leave wood brittle and weak. The choice of treatment depends on the extent of the rot, the age of the property and the severity of the outbreak.

All of the insecticides and fungicides we use have passed stringent British Health and Safety Executive (HSE) tests.

A rotten timber floor void opened up for treatment

Timber

Woodworm Treatment

The term ‘woodworm’ refers to the wood-eating larvae of many species of beetle. While the timber in modern properties is generally already treated, older buildings can be more vulnerable. We tailor the treatment to the severity of the problem, and all of the chemicals and materials we use conform with British Standards and have passed HSE tests.

Our woodworm treatment has a one hour re-entry period, so there is minimal downtime or disruption to your property.

Tell-tale signs

  • Tiny holes in the timber
  • Fine powdery dust caused by adult woodworms boring into the timber
  • Crumbling edges to floorboards and ceiling beams
  • Small dark brown beetles on window sills between May and October months

We also carry out timber treatments and suspended timber floor replacement.

Floorboards lifted to expose the joists in a lived-in room

Below ground

Basement Waterproofing & Tanking

We waterproof basements and cellars in domestic and commercial properties. Tanking stops structures built at ground level or below from leaking as a result of water pressure, and a thorough damp survey tells us which of our two main methods suits your property.

Cementitious structural waterproofing

  • A waterproof layer of plaster is applied to the structure to prevent moisture from penetrating through the wall.
  • Only used if the structure can withstand the added pressure from water already present in the walls.
  • The building must be stable (no subsidence) and not subject to vibrations that may crack the plaster.

Cavity drain membrane

  • A waterproof membrane is attached to the walls so moisture drains to a point where it can be easily pumped out.
  • Ideal if your structure cannot withstand the added pressure of water against the walls, or if your home is subject to vibrations.

Outside the wall

French drains & render plinths

Looking after the outside of a building is key to keeping the inside dry. Our external work includes:

  • Open French drain
  • French drains and pea shingle soak ways
  • Repair and replacement of render plinths
  • Rendering, (including horsehair and lime)
  • Remedial injections
A new render plinth, air brick and gravel drain at the base of a brick house

Air & moisture

Condensation & Mould

Serving both domestic and commercial buildings, we support people experiencing condensation at their properties. Whether you need roof condensation solutions for a poorly ventilated roof, or there is excess moisture in your shower that needs bathroom condensation solutions, we can help, tackling the issue before it develops into a bigger, costly problem.

We also offer professional mould removal and mould fogging. Whether you’re dealing with visible mould growth or hidden spores caused by excess moisture, our team can safely eliminate mould and treat affected areas to prevent it from returning.

  • Advice on condensation management and prevention
  • Pacifier vent installation
  • Mould removal and mould fogging

Warmth

Internal Wall Insulation

Internal wall insulation (IWI) is a smart and affordable way of keeping the walls of your property warm and dry. It can be installed on most construction types, although properties built before 1930, usually with 9” thick solid brick walls, get the most from it. This “fabric first” approach improves thermal comfort while reducing both your carbon emissions and your energy bills.

Benefits of internal insulation boards

  • Stop heat loss
  • Reduce energy costs
  • Improve thermal comfort
  • Lower carbon emissions
  • Alleviate damp/condensation
  • Fast clean installation
  • No change to external aesthetics

Textile based thermal systems

Designed for the dual purpose of saving energy and controlling damp, applied without removing existing plaster work.

  • Ultra thin wall insulation (+/- 4 mm)
  • Flexible and lightweight for easy installation
  • Vapour permeable but waterproof, allowing walls to breathe
  • Can be applied directly to sound plasterboard

£130 per square meter

As a rough guide, including the plaster finish ready for new decoration. Room size, location and construction type decide the final cost.

A plastered room with exposed oak timber framing and beams

Old buildings, repaired the way they were built

We are passionate about old buildings and the important role they play in the rich heritage of our country.

As part of the bespoke service that we strive to offer, we are well-versed in working on the restoration of listed buildings of historical importance and have the experience of using lime putties, horse hair and lime plasters, wattle and daub and chestnut laths when required. We understand the importance of being able to employ both modern and past craft techniques.

Traditional Building Repairs and Lime Pointing

The techniques originally used to build these houses have kept them standing for hundreds of years, and we believe those methods should be respected during renovation. Modern hard cement is often used to replace missing mortar joints, but it isn’t suitable in a traditional building: breathability is compromised and the masonry suffers, with blown brick faces and spalling.

That’s why we use lime mortar for external repointing, and specialise in craft techniques such as lime pointing and cosmetic repair to all types of masonry. Looking after the external fabric of a traditional building is key to maintaining a dry internal space.

From private individuals to commercial clients, such as chartered surveyors, architects and English Heritage, we have a very varied client base.

Two case studies

Chorleywood, Hertfordshire

Heritage works on Hertfordshire historic house

We were invited to survey Solesbridge House, a beautiful Grade II listed building in a semi-rural location in Chorleywood. Built in the early 17th century, the family home was originally 3 cottages set within woodlands that we believe formed part of the Chorleywood House Estate.

The internal walls showed moisture staining and spoiling to the original lime plaster, along with patch repairs made with a hard cement render. Given the age of the property no original damp proof course was expected, and further exposure revealed this to be true. The absence of an original DPC does not mean that rising damp will automatically occur, though: the external ground levels were higher than the internal floor levels, so a French drain around the perimeter was the first step.

Behind the plaster we found tree branches in a sort of lathe and plaster formation. When the lime plaster still wasn’t drying out, we dug a channel in the solid floor at the floor/wall junction and inserted a physical slate damp proof course, using an Arbortech masonry cutting tool, then dried the walls with infra-red thermal lamps and increased ventilation while we monitored the readings.

The finish is a rough cast goat’s hair lime render, keeping the wall breathable: a long term solution using traditional materials.

Buckinghamshire

Lime Pointing on a 250 year old Buckinghamshire farmhouse

Repointing an old red-brick wall from the scaffold

The owner of a 17th-century farmhouse called us about damp showing as staining and salting on the internal walls. They had already been quoted by a large damp proofing company to inject a new damp proof course, but were unconvinced it would solve the problem.

Outside, our surveyor found much of the original lime pointing had degraded, leaving empty mortar joints where rainwater could sit. Some of the masonry was broken and shaped flint, a traditional technique known as “knapping”, and at some point a modern cement had been used to point around it.

  • Provide a dry non-spoiling internal finish which we were confident to guarantee
  • Prevent further erosion of the external mortar joints
  • Prohibit damage to the traditional fabric of the building

The mortar joints were carefully removed by hand using hammer and chisel, not a grinder, so the bricks weren’t damaged, then repointed with a feebly hydraulic NHL lime. Inside, a cavity drainage membrane acted as an isolation barrier, so the family could decorate and have their dining room back very soon after the works.

Why choose us?

  • Surveys carried out by fully qualified PCA surveyors
  • Professional & friendly staff
  • 20 year guarantee on wood treatment
  • 10 year guarantee on structural waterproofing
  • All chemicals & materials conform to British Standards

All works come with our standard company guarantee but also have the option of being underwritten as a fully-insured backed guarantee. Our specialist technicians are fully accredited and trained, and evidence of this is available upon request.

Accredited and checked

Sovereign Approved Contractors
We hold full membership with Sovereign Chemicals and adhere to their strict requirements for workmanship and materials used.
Which? Trusted Trader
Endorsed by Which? with a Hertfordshire Trading Standards Approved endorsement.
Checkatrade
Members since March 2008.
Industry bodies
Our customer service and quality workmanship have earned us accreditations from leading industry bodies, including Safe-Guard, FSB, GPI and Vandex.

What our customers say

Rated 4.9 out of 5 from 35 reviews on Google.

“We used Avant Garde to do a damp survey and then tackle some damp in our dining room in July 2025. They were knowledgeable, efficient and did a tidy job of damp-proofing and re-plastering our walls. We are confident our damp issue has been resolved and we can now get on with decorating. We felt they were reasonably priced and - unlike some other damp firms we have used - did not try and push us into doing unnecessary work. We would recommend this company.”
Jo Stephenson on Google
“Professional, prompt and highly knowledgeable. Our survey showed no damp issues but a requirement for better ventilation ie opening windows more frequently, such a relief that it was not a bigger issue, 100% reccomend and happy with survey service. Thank you.”
Jennifer Webb on Google
“We are very satisfied with the work carried out by Ben and team. The team was professional, efficient, and completed the work to a high standard. They communicated clearly throughout the process and ensured everything was left clean and tidy afterwards. We would be happy to recommend their services.”
Prince D Joseph on Google
“Came out for a fee free inspection of damp. Gave honest advice and recommended an aspect of my roof needed fixing. Then went on to say a roofer may be cheaper to quote. Trust is hard to come buy, I was impressed.”
sophie last on Google
Clare Russell on Google
“We used Avant Garde in 2018 to sort out woodworm in our flat and to floor our cellar. Ben was very knowledgeable and helpful about both issues and the work was done professionally and efficiently. This year, when we realised we had damp we did not hesitate to get back in touch with Ben and he has yet again been very helpful, explaining the problem and work that is needed. We are looking forward to having a damp free home.”
The front of a pebble-dash terraced house

Get our expert advice with an impartial, no obligation survey.

If you have damp in your property, act now. Tell us what you’re seeing and we’ll arrange a visit.

Call free on 0808 164 8398Send us a message

A small company, on purpose

Established in 2003, Avant Garde Damp Solutions has been running continuously since then with hundreds of properties treated across London and the Home Counties, including domestic, commercial and historical buildings.

First and foremost we have deliberately stayed as a small company, as we believe that this is the key to providing a tailored service while constantly building on our reputation for honesty and integrity.

Much of our success comes from being a small company of two teams, which lets us give a “hands on” experience moulded to your needs: a “one stop shop” for all your preservation requirements.

Every job is project managed by our Managing Director, Ben Sullivan, who personally oversees the process from start to finish.

We have a skilled team of expert surveyors and technicians and use only the highest quality treatments. From your initial enquiry through to the completion of a project, we provide friendly, personable service that stands us out from larger companies.

A semi-detached house with a freshly rendered white front

Where we work

With our fleet of fully equipped vehicles, our expert surveyors and engineers travel directly to homes and commercial sites throughout North and West London, Hertfordshire and Buckinghamshire.

  • Amersham
  • Beaconsfield
  • Berkhamsted
  • Camden
  • Chalfonts
  • Chesham
  • Ealing
  • Gerrards Cross
  • Hammersmith
  • Hampstead
  • Hemel Hempstead
  • High Wycombe
  • Kings Langley
  • Maidenhead
  • Pinner
  • Potters Bar
  • Princes Risborough
  • Radlett
  • Ruislip
  • St Albans
  • St John’s Wood
  • Uxbridge
  • Watford
  • Windsor

We’re based at 8-10 Heronsgate Rd, Chorleywood. Not sure if we cover your area? Give us a ring.

Contact us

Give our team a ring or send us an email with your enquiry. Alternatively, fill out the form and we will get back to you as quickly as possible.

Tell us about the problem

The more you can tell us about the property and what you’re seeing, the better.

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Call free 0808 164 8398