Skylight and rooflight fitting in Ystradgynlais

Ystradgynlais is a town in Powys, on the River Tawe. The name means the vale of the river Cynlais, and it is first recorded in 1372. Cynlais may be a personal name or may come from words for a chisel and a stream. The town stood within the former county of Brecknockshire, and today it sits in southwest Powys. The Ynyscedwyn estate, where the area's ironworking was first documented, lies on the town's outskirts.

In the 1600s there were only a couple of houses by the church and a pub, which is now the rectory. By 1801 there were 993 residents living in 196 houses. Iron changed that. The first written evidence of ironworking in the area is a deed of release of 1729 at Ynyscedwyn, and by 1750 one of the seven furnaces in south Wales was there. By 1790 the mineral wealth of the valley was better understood, and improved transport looked essential to use it.

The town's transport tells part of the story. Ystradgynlais railway station operated from 1869 to 1923. The A4067, linking West Cross in Swansea with Sennybridge, ran through the town until the 1970s, when it moved to the bypass that follows the line of the former Swansea Canal. Tynycoed Chapel, between Ynyswen and Penycae, was first built in 1774 and rebuilt in 1829. Since the 1970s, then, the A4067 has kept out of the centre, running instead along the course of the old Swansea Canal on the bypass.

Today the community, which includes Cwmtwrch, Abercraf and Cwmgiedd, had 8,092 people at the 2011 census, and it is the second-largest town in Powys. Count 14.46 road miles out of Swansea, heading north-east, and you are in town, well within our radius. Places nearby that we also cover include Ystalyfera, Seven Sisters, Abercraf and Cwm-Twrch Uchaf.

A town with a history like that has houses from several eras, and the roofs show it in different shapes and covering materials. Older terraces usually have steep, narrow back slopes where one roof window does the job; later estates give more width. Those are general patterns, and your own roof gets read on survey day.

A rooflight that suits one house on a row may not suit its neighbour, because a dormer, an extension or a re-roofing can change what the roof is made of and how it drains. That is why the survey comes first and the written figure comes second.

Planning for an Ystradgynlais house sits with Powys County Council. The Gower AONB is far away, so it has nothing to say about a roof here. The Welsh planning guide on this site walks through how the rules treat a rooflight on a house, and it is worth reading before you decide anything.

The guide covers the cases that sit outside the ordinary one. Flats and maisonettes are outside householder permitted development altogether. A council can withdraw the rights for particular houses with an Article 4 direction, and conditions on an earlier permission can also take them away. Listed houses need listed building consent for a rooflight that would affect their character, applied for through the planning authority and backed by the Historic Environment (Wales) Act 2023.

Doubtful cases are best put to the council's planning team. A Lawful Development Certificate turns the council's view into a certificate and gives formal certainty.

Building Regulations are a parallel process. The Welsh Government's roof-light guidance expects a brand-new rooflight to need approval, citing the cut in the roof and the extra load. Either the local authority's building control team or a registered building control approver can do the checking, and the choice is yours. If the job has to be notified, we make the notification.

The energy figures apply to new and replacement units in existing homes. A roof window should reach 1.4 W/m²K or Window Energy Rating Band B, and a rooflight should reach 2.2 W/m²K, in line with Approved Document L (Wales). Where a replacement roof window on a home of architectural or historic interest cannot reach 1.4, the fallback is 1.2 W/m²K at the centre of the pane, or low-e secondary glazing. Rooflights have no such fallback.

Two further pieces of guidance sit close by. Approved Document N, the Welsh glazing safety guidance, treats the lowest 800 mm of walls and partitions, and the lowest 1,500 mm of doors and side panels, as critical locations where glass should break safely, be tough or be made of small panes. Approved Document F (Wales) covers ventilation, and says ventilation after a window replacement should not fall below what the home had before. A roof window with a trickle vent can keep that balance.

Take an attic bedroom with a tired roof window. The first question is what is already there. On a VELUX, a stamped label near the top of the opening sash carries a code, and our page on VELUX size codes explains how to read it. Windows made since 1968 have one. The table below gives three examples from VELUX's own list, and a code like these settles the size of the opening before anyone goes up a ladder.

A new roof window in the same opening can be a top-hung type, which swings out above your head, or a centre-pivot, which turns so the outside glass faces the room for cleaning. If the room is a bedroom and you leave the window ajar, the electric version can include a sensor that shuts it as soon as rain is detected. See electric opening rooflights for what is on offer.

Fresh glass in an unchanged frame is outside the energy rules' definition of building work. A complete new window falls inside the definition. If the sealed unit has clouded between the panes, the glazing seal has gone, and misted rooflight replacement is a job we take on.

Extensions bring flat roofs. Over a kitchen, a flat roof rooflight usually needs a fall so the rain can leave its kerb, and a roof lantern prompts a planning question for the council at survey. Landings and halls with no outside wall can take a sun tunnel, a little roof dome with a mirrored tube down to the ceiling.

Ventilation follows any window change. Vents that the old window carried should be matched on the new one, at no smaller a size, and controllable by the people who live there or automatically. That is checked at the same visit.

Each job starts with the free survey. A fixed written quote follows it. A 10-year workmanship guarantee, in writing, comes with the finished work. Ring 01792 929062 or book the survey online.