January 2026 was Northern Ireland's wettest January in 149 years.
The Met Office recorded 195.6 mm of rainfall — 170% of the monthly average — on top of an already wet November and December.
County Down had its wettest January on record, and Katesbridge logged 100.8 mm in a single day — more than double its previous site record.
For most people that meant cancelled journeys and waterlogged gardens. For older buildings, sustained saturation like this tells a slower, more expensive story — one that may not show up for weeks or months.
Why Sustained Rainfall Is Different from a Single Storm
A brief downpour runs off. Months of above-average rainfall lets moisture creep in properly:
Solid masonry (common in pre-1950s NI properties) absorbs progressively from the outside in
High water tables push moisture up through foundations, even where a damp proof course exists
Overwhelmed gutters deposit water against walls for weeks at a time
Small cracks or failed pointing that held through a dry summer let water in under sustained driving rain
What to Watch For
Rising damp — groundwater drawn up through masonry with no effective (or bridged) damp proof course.
Look for:
A band of staining on lower walls, below roughly 1.2m
Tide marks or salt deposits
Peeling paint at low level
A musty smell
If it dries back in summer and returns in wet weather, it's more likely condensation or penetrating damp. A professional inspection tells you which — and the treatment differs significantly.
Penetrating damp — moisture coming in through the wall fabric rather than up from the ground.
Watch for:
Map-shaped damp patches that correspond to where rain hits the outside wall
Damp that appears after heavy rain and fades over following weeks
Salt deposits or spalling on brick
Masonry waterproofing suits walls that are otherwise sound but have become porous. It's not a substitute for fixing failed render, pointing or guttering first.
Wet rot — timber decay from persistent dampness, most likely in:
Ground-floor joists and sleeper walls
External joinery
Skirtings
Any timber near overflowing gutters
It feels soft and spongy when probed, and darkens in colour.
Dry rot — counterintuitively more likely once the heating goes back on. Wet timber passing through 20–30% moisture content as a building dries out is exactly the range dry rot needs to germinate.
It's the most damaging fungal attack a building can suffer, spreading through masonry to infect timber well away from the source. Watch for:
A musty, mushroom-like smell in confined spaces
Cuboidal cracking in timber
Cotton-like mycelium
Orange-brown fruiting bodies
Don't attempt to treat it yourself.
Condensation — still the most common damp problem in NI homes, especially now that wet building fabric plus heating creates warm moist air meeting cold walls.
Many homeowners assume mould patches are rising or penetrating damp when it's actually condensation, which needs a different fix entirely — a chemical damp proof course injection won't solve it.
What to Do Now
Check gutters, downpipes, pointing and render externally; clear blockages and look for gaps.
Check ground levels against the external wall — soil or paving within 150mm of the damp proof course is a common cause of apparent rising damp.
Check ground-floor rooms for low-level damp, salt deposits, soft skirting boards or a musty smell.
If you have a suspended floor, check the subfloor ventilation bricks are clear.
If any of this rings a bell, it's worth getting an expert opinion rather than guessing — give us a call and we can arrange a survey.
Radication Ltd has been surveying and treating damp, rot and timber problems across NI — postcodes BT1 to BT94 — covering Belfast, Bangor, Lisburn and towns throughout the province.