# Opening for Sliding Doors Dublin | Rear Wall Steel & Goalposts > Widening a rear wall opening for sliding or bifold doors in Dublin: steel beam or goalpost design, propping and sign-off by a Chartered Engineer. Fixed fee. URL: https://structuralengineer.ie/rear-wall-opening-for-sliding-doors/ # Opening for Sliding Doors: Widening a Rear Wall in Dublin Widening the back wall for a run of sliding or bifold doors: a steel beam or goalpost frame carrying the floor and roof, with enough stiffness that the doors still slide. [Call 01 270 9764](tel:+35312709764) [Get a fixed fee](#quote) _Image: Steel goalpost frame in a widened rear wall opening ready for sliding doors in an Irish semi_ - I.S. EN 1993-1-1 Steel design - I.S. EN 1996-1-1 Masonry design - I.S. EN 1997-1 Geotechnical design - TGD A Structure - TGD L Energy Last updated: 14 October 2026 · Reviewed by Joachim Louw, CEng MIEI [StructuralEngineer.ie](https://structuralengineer.ie/) designs openings for sliding doors and bifolds in the rear walls of Dublin homes, from a 1970s semi to a Victorian terrace. Widening the back wall is different from removing an internal wall. The rear wall carries the first floor and often the roof, it is exposed to wind and weather, and the doors themselves fail if the steel above them deflects more than a few millimetres. Joachim Louw (CEng MIEI) designs the steel, the bearings and the propping, and inspects before it is covered. The usual answer is a steel goalpost: a beam on two posts down to the foundations, so the opening isn't limited by how much the masonry beside it can carry. ## What happens on the first visit On the visit the engineer checks what the rear wall carries (floor joists, roof, any upstairs window above the opening), the masonry each side of the new opening, and what's below ground where posts will land. - Check joist direction and roof bearing on the rear wall - Note upstairs windows above the opening and their lintels - Measure the door manufacturer's opening and the tolerance it needs - Check the masonry piers either side of the opening - Assess foundations where goalpost posts will land - Plan propping and weathering while the wall is open ## Why door makers care about deflection Large sliding and bifold doors have tight tolerances. If the beam above sags under the floor load, the head of the frame pinches and the doors bind. Manufacturers typically limit deflection of the head to a few millimetres, much tighter than the span/360 used for a plastered ceiling. The beam is designed to the door maker's figure, which often means a deeper or stiffer section than strength alone needs. Thermal bridging is the other issue. Steel through a cavity wall conducts heat. The design includes the cavity closure and insulation detail at the head and the posts to meet Technical Guidance Document L. ## Planning and certification Widening a rear opening on its own is usually exempted development, since it doesn't change the front elevation. As part of an extension, it falls under the extension's exemption or permission. Either way, Part A (Structure) and Part L (Energy) apply, and an opinion of compliance based on an inspection before covering is what you'll need at sale. ## What's included - Site visit by a Chartered Engineer - Beam or goalpost design to the door maker's deflection limit - Post foundations and base plates - Thermal bridging and cavity closure detail - Propping and weathering sequence - Steel schedule for the fabricator - Inspection before covering - Signed opinion of compliance Fixed fee confirmed in writing before the visit. ## Standard lintel, a strength-only beam, or a door-ready design Why some new doors stop sliding within a year. | Check | Standard lintel | Strength-only beam | Designed to the door's deflection limit | | --- | --- | --- | --- | | Carries the floor and roof safely | maybe | Yes | Yes | | Deflection within door maker's limit | No | No | Yes | | Thermal bridge detailed | No | No | Yes | | Foundations checked under posts | No | sometimes | Yes | Talk to the engineer 01 270 9764 Mon–Fri 8:00–18:00. Callback the same working day. [Call now](tel:+35312709764) Fixed fee confirmed in writing before the visit. Standards we design to - I.S. EN 1993-1-1 Steel design - I.S. EN 1996-1-1 Masonry design - I.S. EN 1997-1 Geotechnical design - TGD A Structure - TGD L Energy Before you book: costs and rules - [Cost to Remove a Load-Bearing Wall in Dublin (2026)](https://structuralengineer.ie/guide/load-bearing-wall-removal-cost/) - [RSJ vs Lintel vs Steel Beam: What's the Difference?](https://structuralengineer.ie/guide/rsj-vs-steel-beam-vs-lintel/) - [Extension Engineer Fees in Ireland: What a Structural Engineer Charges (2026)](https://structuralengineer.ie/guide/extension-structural-engineer-cost/) How the job runs ## How a rear-wall opening is designed and signed off - 01 ### Call and fixed quote Send the door spec and opening width. You get a fixed fee in writing. - 02 ### Site visit Rear-wall loads, piers, foundations and upstairs openings are checked. - 03 ### Design Beam or goalpost, foundations, thermal detail and propping. - 04 ### Inspection and sign-off The steel is inspected before covering, then the opinion of compliance is issued. Opening the back wall for big doors? Get it designed to the door maker's limit. Fixed fee confirmed in writing before the visit. [Call 01 270 9764](tel:+35312709764) [Request a fixed fee](#quote) Questions ## Openings for sliding doors: common questions **How wide can I make the opening for sliding doors?** With a steel goalpost founded on proper foundations, openings of 4 to 6 m are common in Dublin semis, and wider is possible. The limits are usually the door system, deflection and access to get the steel in, rather than strength. **Why did my new sliding doors start sticking?** Usually the beam above is deflecting more than the doors can tolerate, because it was sized for strength but not stiffness. Door makers set tight deflection limits. The fix is either stiffening or replacing the beam, which is why designing to the door's limit at the start matters. **Do I need planning permission to widen my back wall?** Usually not on its own, since it doesn't affect the front of the house. As part of an extension, the extension's exemption or permission covers it. Building Regulations Parts A and L apply either way. **Is a steel goalpost always needed?** Not always. Narrower openings in sound masonry can work with a beam on padstones. Wide openings, weak piers or heavy loads from above make a goalpost the better option. **What areas do you cover?** Dublin and the Greater Dublin Area (Kildare, Meath and Wicklow). Site visits are booked from the Blackrock office. Site visit usually within 5 working days. ## Related services [### Extensions Foundations, steel and BCAR sign-off for rear and side extensions, including the new 45 m² exemption.](https://structuralengineer.ie/structural-engineer-for-extensions/) [### Load-Bearing Wall Removal Steel beam and padstone design, propping, inspection and a signed certificate for knock-throughs.](https://structuralengineer.ie/load-bearing-wall-removal/) [### RSJ Calculations Beam and padstone calcs and a steel schedule for builders who already know what they need.](https://structuralengineer.ie/rsj-calculations/) Next step Get a fixed fee for your rear-wall opening Call [01 270 9764](tel:+35312709764), or send the details and we'll call you back. Request a fixed engineering fee Prefer to talk? [Call 01 270 9764](tel:+35312709764). A live person answers during office hours.