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Loft insulation being installed in a London property by GMAS Group

Energy · Insulation

Insulation, and the damp risk that comes with it.

Loft, cavity, underfloor and internal wall insulation. It is the cheapest route up the EPC bands, and done badly on a solid wall it is also the fastest way to create condensation. We survey before we specify.

What we do

Warmer, without
trapping moisture.

Loft insulation

Topping up to current depth, with the joists crossed rather than filled, and eaves ventilation kept clear.

Cavity wall insulation

Where the cavity is clean, suitable and not exposed to driving rain. Where it is not, we will say so, because a wet cavity is worse than an empty one.

Internal wall insulation

Solid wall properties, using a breathable build-up so the wall can still dry inwards. The single biggest EPC gain on a Victorian house and the one most often botched.

Underfloor insulation

Suspended timber floors insulated between the joists with the underfloor ventilation preserved.

Damp proof course

Injected or physical DPC where the original has failed, then replastering in the correct sand and cement or lime system.

Tanking

Cellars, basements and retaining walls tanked with a cavity drain membrane and a managed drainage route.

EPC re-assessment

A fresh certificate lodged on completion, so the work shows up in the rating rather than just the fuel bill.

How it works

From survey
to new EPC.

Survey

We check construction, moisture, ventilation and the current EPC recommendations before proposing anything.

Specification

We tell you which measures move the rating and which are marketing, and give you the order to do them in.

Fixed quote

Measures, materials, making good and any replastering itemised, with the EPC assessment shown separately.

Install and re-assess

Works carried out, ventilation checked, and a new EPC lodged if the job was rating-driven.

Common questions

Answered
plainly.

Will insulation cause damp?

It can, if it is fitted without thinking about moisture. Internal wall insulation on a solid wall moves the cold surface behind the insulation, and if warm moist air can reach it you get interstitial condensation you never see until it does damage. That is why we survey moisture and ventilation first and use a breathable build-up on solid walls.

Which measure gives the biggest EPC improvement?

On a typical London Victorian terrace, usually solid wall insulation, then loft insulation to current depth, then heating controls and low-energy lighting. On a post-war property with an empty cavity it is often cavity fill. It genuinely depends on the property, which is why we look at the EPC recommendations rather than guess.

Should I insulate my cavity?

Only if the cavity is clean, wide enough, free of debris and not on a wall that takes driving rain. West and south-west facing London walls on exposed corners are the ones to be careful with. If yours is not suitable we will tell you, because a saturated cavity is a much more expensive problem than an uninsulated one.

What is the difference between damp proofing and treating damp?

Damp proofing installs a barrier, usually against rising damp, which is much rarer than the industry implies. Most damp we are called to is penetrating damp from a defect, or condensation from ventilation. Injecting a DPC into a wall with a leaking gutter above it wastes your money and fixes nothing, so we diagnose first.

Do you lodge a new EPC afterwards?

Yes, where the work was done to improve the rating. There is no point doing the works and leaving the old certificate on the register.

Which areas do you cover?

All 32 London boroughs, with a focus on west and south-west London.

Get started

Tell us the property
and we will survey it.

A site visit, an honest recommendation and a fixed written quote. London-wide.

Diagnosis first

Damp treatment that starts with finding the water.

Damp proofing has a poor reputation in London and it is largely deserved, because the standard damp treatment is sold before the damp is diagnosed. There are three separate problems that look identical on a wall, and only one of them is treated by injecting a chemical damp proof course.

Rising damp

Genuine rising damp is far less common than the industry suggests. It shows as a tide mark up to about a metre, with salts in the plaster, and it is usually caused by a bridged or failed damp proof course rather than by no course at all. Raised ground, a new path, added render across the course or a flower bed against the wall will all bridge it, and where that is the cause, lowering the ground solves it and injecting does not.

Penetrating damp

Water coming through the wall from a defect outside, most often a blocked or leaking gutter, cracked render or perished pointing. It is the most common damp we are called to. The treatment is fixing the defect, then letting the wall dry, then replastering. Any damp specialist who quotes to inject a wall that has a leaking downpipe above it is treating the stain rather than the cause.

Condensation

Moisture produced inside the property settling on cold surfaces, showing as black mould in corners, behind furniture and around windows. No damp proofing course will touch it. It is solved with ventilation, heating and insulation, and it is the reason we survey ventilation before proposing any damp treatment at all.

Guarantees

Where a chemical damp proof course is genuinely the right answer, the installed system carries the manufacturer's guarantee, and we give you the paperwork rather than a verbal assurance. A guarantee on the wrong treatment is worth nothing, which is why the diagnosis comes first.

Coverage

Areas we cover.

We take damp proofing and insulation work across all 32 London boroughs. Most of our work is in west London, in Shepherd's Bush, Hammersmith, Fulham, Kensington, Chiswick and White City, and in south west London, in Putney, Wandsworth and Wimbledon. We also work in south east London, in Greenwich, Blackheath and Lewisham.

If your property is outside these areas, call us anyway. We travel across London and will tell you honestly if a job is too far to price properly.

Message us
Call GMAS on 07498 597339