Damp proofing in Conisbrough, Mexborough and Edlington

West of Doncaster the River Don runs past Conisbrough Castle and the old pit villages of Denaby Main and Cadeby to Mexborough, near where the Dearne joins it (Wikipedia: Mexborough). This guide explains what that means for damp, where flooding has hit and when a survey is worth it. It is general information, not a diagnosis.

Flooding in the Don valley

The council’s Section 19 flood investigation into November 2019 records 25 properties flooded within Conisbrough. Ten were around Dufton’s Close and Minneymoor Hill, flooded by the River Don, and the report notes there are no raised defences protecting the north part of Conisbrough. Another 13 were on New Hill and Low Road, flooded by Kearsley Brook, which is on the Environment Agency’s register of rapid response catchments. The Environment Agency also holds a flood record for Conisbrough in June 2007, and the report cites earlier floods in 1875, 1886, 1939 and 1947.

The same report records properties affected at several locations in Mexborough, and in Denaby Main and Old Denaby, where some flooding came directly from the Don. Mexborough Lock recorded its highest ever level, 14.65m above ordnance datum, at 05:45 on 8 November 2019. Rest centres and community hubs were set up in the worst affected areas, including Denaby and Mexborough. (Doncaster Council: Section 19 flood investigation report, PDF).

If your home flooded and the damp has never fully cleared, start with damp after flooding in Doncaster. Walls and floors can hold water long after they look dry, and replastering too early can trap it.

Limestone, slopes and soils

Conisbrough Castle’s keep, built around 1180 to 1190, is made of magnesian limestone and stands on a rocky magnesian limestone spur. The castle is a Grade I listed building and a scheduled ancient monument (Wikipedia: Conisbrough Castle). The Section 19 report says British Geological Survey mapping shows dolostone bedrock across most of Conisbrough, with mudstone, siltstone and sandstone along Kearsley Brook, and soils described as slowly permeable and seasonally wet.

For homes, that matters in two ways. On a slope, a house can have ground built up against one wall and not the other, so damp may appear on the uphill side only. And older houses built of local stone, or with stone dressings, are solid-walled and need to be able to dry out. The Society for the Protection of Ancient Buildings warns that old buildings become damp if an impervious layer is applied, because it stops water in the structure evaporating, and that strong cement renders tend to crack and trap water (SPAB: the need for old buildings to breathe, PDF). Conisbrough has a conservation area, recorded in the government’s planning data from 1974, and the council adopted an amended boundary on 18 October 2022 (planning.data.gov.uk: Conisbrough; The Gazette, notice 4194563). Mexborough also has a conservation area (planning.data.gov.uk: Mexborough). Check with City of Doncaster Council before changing walls, windows or render in either.

Colliery villages and their terraces

Two shafts were sunk at Denaby Main in 1863, and the village was built by the Denaby Main Colliery Company to house its workers and their families. Denaby Main colliery drew its last coal in 1968 (Wikipedia: Denaby Main). Cadeby Main was sunk in 1889 and began production in 1893; on 9 July 1912 two explosions there killed 88 men, including rescuers, and three more died later of their injuries (Wikipedia: Cadeby Main Colliery).

At Edlington, two shafts were sunk for Yorkshire Main Colliery in 1909 and 1910, and the pit closed on 11 October 1985 (Wikipedia: Yorkshire Main Colliery). New Edlington was built to house the workers who came with the sinking, between 1909 and about 1922 (Wikipedia: Edlington).

How older solid-wall terraces get damp

Many older terraces here have solid brick walls, suspended timber floors and back yards that have been concreted or raised over the years. In homes like these, the usual problems are:

Bridged damp proof courses. Yards, paths and front gardens raised above the DPC, or render taken down to the ground, let moisture bypass it. Clearing the bridge often helps more than an injection. See rising damp and damp proof courses.
Blocked air bricks. Without airflow, the void under a timber floor stays damp and joists can rot.
Rain getting in. Worn pointing, cracked render, leaking gutters and shared chimney stacks on terraces are common causes of patches that grow after rain. See penetrating damp.
Condensation. Cold solid walls, small rooms and sealed-up fireplaces make mould in corners and behind furniture likely. See condensation or rising damp? and black mould removal and causes.
Cellars. Where a terrace has a cellar, damp walls and floors are normal unless it has been waterproofed. See cellar damp and tanking in Doncaster.

Cracks, subsidence and damp

Cracks matter because they can let rain into a wall. If you think the damage comes from coal mining, the GOV.UK guide to your rights explains that the mine owner will carry out repairs, that rights come from the Coal Mining Subsidence Act 1991, that claiming is free, and that claims must be submitted within 6 years of the damage becoming apparent (GOV.UK: coal mining subsidence damage, a guide to your rights). The Coal Authority became the Mining Remediation Authority in November 2024, and its statutory responsibilities did not change (GOV.UK, November 2024). You can view selected coal mining information online at no cost (GOV.UK). To report a hazard such as a hole or collapse, the Mining Remediation Authority’s 24-hour line is 0800 288 4242.

What to check yourself

Check your address on GOV.UK: check your long term flood risk, which shows risk for an area rather than a specific property, and sign up for free flood warnings.
Walk round the outside. Is the ground or yard surface below the damp proof course on every wall, are air bricks clear, and do gutters and downpipes run freely?
Note any cracks or sticking doors, and when the damp is worst: after rain, in cold weather or all year.

When to get a damp survey

Get a survey if damp keeps coming back after the simple checks, if plaster is blowing or salts are showing, if you are buying, or if a firm has recommended treatment without explaining the cause. A good survey looks inside and out, records moisture readings and photos, checks ground levels, air bricks, gutters and ventilation, asks about any flooding or cracking, and explains in writing what is causing the damp and why any work is needed. Our damp survey guide explains what a report should include. If you rent, report damp and mould to your landlord in writing; see damp and mould in rented homes in Doncaster.

What to tell us

Use the enquiry form with your postcode (S64 for Mexborough, DN12 for Conisbrough, Denaby and Edlington), the type and rough age of your home, where the damp is, whether it changes with rain or cold weather, and whether the house has flooded or cracked. With your consent, we will pass your enquiry to a local damp and mould professional who can talk it through and, if needed, arrange a survey and written quote.

Sources and further reading

Doncaster Council: Section 19 flood investigation report, September 2020 (PDF); Wikipedia: Conisbrough Castle; planning.data.gov.uk: Conisbrough conservation area; The Gazette: Conisbrough conservation area boundary, notice 4194563; planning.data.gov.uk: Mexborough conservation area; Wikipedia: Denaby Main; Wikipedia: Cadeby Main Colliery; Wikipedia: Yorkshire Main Colliery; Wikipedia: Edlington; Wikipedia: Mexborough; GOV.UK: coal mining subsidence damage, a guide to your rights; GOV.UK: Mining Remediation Authority; GOV.UK: new era as Coal Authority becomes Mining Remediation Authority; GOV.UK: access coal mining information and data; SPAB: the need for old buildings to breathe (PDF); GOV.UK: check your long term flood risk; GOV.UK: sign up for flood warnings.

Areas we cover

Related guides

Frequently asked questions

Did Conisbrough flood in November 2019?

Yes. The council’s Section 19 flood investigation records 25 properties flooded within Conisbrough: 10 around Dufton’s Close and Minneymoor Hill from the River Don, and 13 on New Hill and Low Road from Kearsley Brook. The Environment Agency also holds a flood record for Conisbrough in June 2007.

Is damp in an old Denaby or Edlington terrace always rising damp?

No. Raised yards and paths, render over the damp proof course, blocked air bricks, leaking gutters and condensation on cold solid walls are all common in terraces of that age. Ask for the cause to be established in writing before agreeing to an injected damp proof course.

I have cracks and damp. Could it be mining subsidence?

Possibly, but cracks have many causes. The GOV.UK guide to coal mining subsidence damage explains how to claim, says claiming is free and that claims must be submitted within 6 years of the damage becoming apparent. Mention the cracks to any surveyor, because they can let rain into a wall.

Is Mexborough covered even though it has an S64 postcode?

Yes. Mexborough is in the City of Doncaster, and we take damp and mould enquiries from S64 as well as DN postcodes. Put your postcode in the enquiry form.