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Damp proofing in Barnet: an independent survey first
Barnet is mostly interwar suburb on London clay, from Finchley and Hendon to Edgware and Mill Hill, with Hampstead Garden Suburb as an Arts and Crafts conservation area governed by covenants as well as planning. Interwar houses almost always have a working damp proof course, so a damp proofing quote here is a prompt to find out what has bridged or bypassed it. ATi carries out no remedial work.
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Why the survey comes before damp proofing in Barnet
A great deal of the damp proofing sold in Barnet is sold to a wall that is wet for another reason: a lightwell or patio above the old course, a defective gutter on a party parapet, a bathroom extract ducted into a void, or condensation in a flat that has lost its air changes. We do not sell damp proofing or any other remedial work, so the survey has one job, which is to say which of those it is.
The quotes we review most in Barnet are injection along front and side walls where drives have been paved above the course, injection for damp at the junction with a rear extension where the floor was set too high, and damp proofing for mould on cold walls. In Hampstead Garden Suburb, proposals that would never satisfy the Trust are also common.
In Barnet, a large share of homes are flats, and damp proofing quotes are often given to a leaseholder for a problem that belongs to the building. Before paying, check whether the water is coming through the roof, the external walls, the front area or a shared drain, because under most leases those are the freeholder's to repair. Our report states the source and the route, with the evidence a managing agent needs.
What the different damp proofing treatments are for
Injection is meant for rising damp in a wall with no working course. Tanking and cavity drain membranes are for below ground walls, which in Barnet usually means a lower ground floor or a cellar. Salt resistant replastering deals with contamination left by long term damp. Ventilation and heating deal with condensation. Each is valid for its own fault and useless for the others.
London's solid walled terraces were built to breathe. Sealing one with cement render or tanking above ground tends to push moisture somewhere else in the building, frequently into the flat next door or the floor above.
Barnet walls, and what they actually need
Barnet's interwar houses have cavity walls with courses that need keeping clear, suspended timber floors with airbricks that need to stay open, and extensions whose junctions need detailing properly. On clay, gardens stay wet and drainage matters. Arts and Crafts houses need repairs that respect their design.
- Cutting back paving and adding drained channels where drives bridge the course
- Correcting extension junctions where the floor or the cavity tray bridges the old wall
- Reopening airbricks and ventilating suspended timber floors
- Ventilation and cold spot repairs for mould
Extensions and the original damp proof course
A great many Barnet houses have rear or side extensions, and the junction between old and new is one of the commonest sources of damp. If the extension floor was laid higher than the original course, the old wall is bridged at its base. If the cavity tray where the extension roof meets the house was missing or badly lapped, rain runs down inside the old wall.
Both show as damp at the junction, inside the original house, and both get quoted for injection. Neither is fixed by it. The survey identifies which, and the repair is to the junction.
What proper damp proofing involves in a London building
- A diagnosis in writing, with readings, before any specification
- External and communal faults identified and assigned: parapets, gutters, lightwells, shared drains
- A new damp proof course only on a Barnet wall that genuinely lacks a working one at low level
- Breathable or salt resistant replastering chosen for the wall, not a default system
- Consent considered where the building is listed or in a conservation area
- A record of what was done and why, which a future buyer's surveyor will ask for
Avoiding an unnecessary damp proofing bill
- Treat a free survey as a sales visit and do not sign on the day
- Ask how condensation, rainwater and ground level were excluded
- Ask whether any of the cause sits in the common parts and who should pay
- Be cautious of tanking an above ground wall in a Barnet conversion
- Ask for the readings, their locations and the height of plaster removal in writing
- If a purchase depends on it, get the report before exchange, not after
When a damp proof course is the right answer
Some Barnet walls do need a damp proof course: a solid wall with no course, or one that has been bridged internally by a solid floor, that remains wet at low level once every external source has been eliminated. Where we find that, the report specifies it plainly, with the height and finish, so you can obtain like for like quotes.
The survey fee is published and fixed before the visit. In Barnet, where replastering and making good in a period flat is expensive and disruptive, establishing whether the work is needed before it starts is the economical step.
The report gives you the cause, the responsibility and a specification. In Barnet that often means a letter to a freeholder or managing agent with the evidence attached, before any work inside the flat is considered.
For the full picture of what a survey here involves, see damp surveys in Barnet.
Around Barnet
Finchley, Hendon and Golders Green
Interwar and Edwardian houses, many extended. Driveways, extension junctions and suspended floors are the usual causes.
Hampstead Garden Suburb
Arts and Crafts houses with covenants and conservation controls. Repairs must be sympathetic, and the report is written with that in mind.
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Damp proofing questions in Barnet
Does our Finchley semi need a new damp proof course?
Rarely. Interwar houses in Finchley, Whetstone and Hendon were built with slate or bitumen courses that usually still work. Where a wall is damp at low level, the cause is most often a block paved drive, a patio or an extension floor laid above that course, or mortar and rubble bridging the cavity at its base. Correcting those is groundwork and detailing, and it lasts.
Can we damp proof a house in Hampstead Garden Suburb?
Work to houses in the Suburb is controlled by the Trust and the council, and proposals that change the character of the house are often refused. Damp in these Arts and Crafts houses is usually rainwater, ground levels or ventilation rather than a failed course, and the report recommends repairs of the kind that are generally acceptable, flagging anything likely to need consent.
Why is the wall where our extension joins the house damp?
Usually one of two detailing faults. Either the extension floor was set above the original course, bridging the old wall at its base, or the cavity tray where the extension roof meets the house was missing or badly lapped, letting rain run down inside the old wall. Both show as damp at the junction, and both are repaired at the junction.
Our bedroom has black mould. Has a firm rightly quoted damp proofing?
No. Black mould grows where surfaces are cold and the air is humid, which is condensation. A damp proof course stops ground moisture rising and has no effect on it. Extraction, heating patterns, trickle vents and insulating a cold lintel or reveal are what help, and the survey measures which matters most.
Can you check a quote before we sign it?
Yes. Send it with your request. The report states which parts are supported by the evidence, which are not, and anything that should be done first, so you can go back to the contractor with specific questions.
Do you carry out work or recommend contractors?
Neither. ATi surveys and reports only and takes no referral fees, which is what allows the report to say plainly that no damp proofing is needed when that is the finding.
Can you recommend a damp proofing company in Barnet?
We do not refer work or take commission, which keeps the report independent. What we give you instead is a specification precise enough that any competent contractor can price it, and we are happy to read the quotes you receive against it.
Book a survey before you pay for damp proofing
An independent survey before any damp proofing in Barnet. We do no remedial work. Written report within 24 hours.
Request a Survey or call 020 3355 4944