Roof & Exterior Cleaning At Y Mochyn Du, Cardiff
We were brought in as part of the refurbishment at the Cathedral Road pub, cleaning the roof, clearing the gutters and treating the tiles before it reopened as Y Mochyn Du on the 17th of September.
Project Overview
We have worked at this pub before, professionally pressure washing the patio and customer seating. This time, though, the job was the roof, and it had a deadline.
The venue closed at the start of September for a refurbishment, with the owners bringing back the Y Mochyn Du name that had been dropped in 2018. Reopening was set for 17 September, which meant whatever we did to the outside had to be finished and looking right for the day the doors opened again.
The roof was the main piece of work. Moss and algae had built up across the elevations, worst on the shaded sides and under the trees at the back, and enough had come down over the years to block the gutters. That came off, the gutters were cleared, and a biocide was applied to keep the growth from returning.
Patio & Customer Areas
We first visited the pub well before the refurbishment, when it was still trading as Brewhouse & Kitchen. That job was the patio and outside seating, which get walked over all day in a venue this busy.
We went over the paving with commercial pressure washers and a professional surface cleaner. The surface cleaner is what keeps it even. A lance on its own leaves stripes across an area this size, and you only notice once it dries.
A chemical treatment afterwards dealt with what was still sitting on the surface, then the whole lot was rinsed down and left ready for the next service.
Roof Cleaning
The tiled roof, however, was the main event. Moss, algae and organic growth had built up over years, heaviest on the shaded elevations and under the mature trees at the back.
Older tiles don’t take kindly to being blasted, so we used our power-pole system with a Mosmatic surface cleaner. It cleans from safe access positions, keeps pressure under control, and removes moss in stages rather than all at once.
We worked through each elevation separately because they weren’t all in the same condition.
Gutter Clearance
Whatever comes off a roof ends up in the gutters, and these had plenty.
Our SkyVac gutter vacuum pulled out the moss, leaves and debris until the drainage ran properly again. We cleaned and tidied everything below afterwards, which matters more than usual outside a pub.
Biocide Treatment
Cleaning a roof removes surface growth, but it doesn’t touch what’s rooted in the tile itself, which is why some roofs green up again within a season.
So once the roof was clean, we applied a professional biocide. It works on the algae and lichen left on the surface, slows regrowth, and the roof keeps improving for weeks after we’ve packed up.
Access Around The Building
Different roof elevations, restricted corners, and a venue that stayed open meant access required planning before anything came off the van.
Equipment used included:
- Specialist roof power-pole system
- Mosmatic roof surface cleaner
- SkyVac gutter-vacuum system
- Commercial pressure-washing equipment
- Mobile access tower
- Professional chemical and biocide treatments
The Result
Years of moss off the tiles, gutters running again, and a building ready for the day it reopened. All this work, combined with the earlier patio work, brought the outside of the venue back together.
Being part of a relaunch means working to someone else’s date. The pub had an opening day booked and press interest in the name coming back, so the exterior had to be finished on time, not nearly finished.
Y Mochyn Du reopened on 17 September 2026, eight years after the name was dropped and Wales Online covered the story.
Some Before & After Photos
Drag the handle across each photo to compare.
