Ireland Wet-Area Waterproofing: What TGD Part C Doesn't Cover

The requirement

Straight answer: TGD Part C sets no wet-area waterproofing rule. There is no clause for a shower wall, a wet-room floor or a bath upstand. The working detail sits in two standards instead: BS 5385-1 and BS 8000-11, run through NSAI.

TGD C is called “Site Preparation and Resistance to Moisture”. The current edition is the 2023 amendment. It is the guidance to Part C of the Second Schedule to the Building Regulations 1997–2023. Like the UK version, it deals with the shell of the building. That means site prep, ground moisture, radon, and keeping rain out of walls and roofs. It never gets down to shower or wet-room floor detail. No membrane extent. No wall height. No tanking spec.

So a claimed “TGD says” figure for a shower wall is not real. No such number sits in TGD Part C. Irish rules leave wet-room tanking to standards, the same way the UK does.

Where the actual numbers live

Irish work follows the same route as the UK. NSAI, the National Standards Authority of Ireland, takes on the British Standards. BS 5385-1 covers the design and fitting of internal wall tiling. That means ceramic, natural stone and mosaic. BS 8000-11 covers workmanship on site. These two hold the wet-room tanking detail.

Both are paid standards. You cannot read the full text for free. France’s DTUs and Germany’s DIN 18534 work the same way. So does the UK. This page names the standards but does not quote their figures.

The membrane maker’s guide also does a lot of the work. So do Irish Agrément-type product certs. A real Irish wet-room spec most often reads “BS 5385-1 plus the membrane maker’s system”. It is rarely one code clause.

What this means on site

There is no TGD clause to point to. Your route runs through the standard and the product:

1. Get the current BS 5385-1 and BS 8000-11 text. Buy it through NSAI or BSI. Do this before you price or detail any wet-room tanking. Work from the current edition. Never trust a figure you recall from an old job.
2. Follow the membrane maker’s system. Coats, cure times, primer, upstand heights, drain detail. That is the level an inspector or building surveyor checks on site.
3. Keep the paperwork. Save the standard you worked to and the product data sheet. Keep proof of a correct install. Part C has no clause number to cite. This record shows you met its general performance rule.

Related

• Part of the Irish Building Regulations hub. One national rule book, with the TGDs and the plain-English guides.
• Building the room around it? See Does Ireland have a minimum ceiling height?. Another TGD that sets no fixed figure where you might expect one.

Sources

• Technical Guidance Document C, “Site Preparation and Resistance to Moisture” (2023 amendment) — confirmed to contain no dedicated wet-room, shower or bathroom waterproofing clause; its scope is site preparation and envelope moisture resistance. Read it at gov.ie.
• BS 5385-1, “Wall and floor tiling — Part 1: Design and installation of internal ceramic, natural stone and mosaic wall tiling in normal conditions. Code of practice”, and BS 8000-11 “Workmanship on building sites” — the standards actually governing wet-room tanking detail in Ireland, distributed/recognised via NSAI. Paid BSI publications; not reproduced here. See nsai.ie and bsigroup.com.

Read this first. TGD C is a national document — Ireland runs one Building Regulations regime, unlike the UK’s devolved nations. BS 5385-1 and BS 8000-11 are paid publications; always confirm the current edition directly with NSAI or BSI before relying on any detail from them. (Verified against TGD Part C, 2023 amendment, as at 2026-07-31.)