Flat roof leak detection in Vienna, Lower Austria and Burgenland

Key facts at a glance

For you as a private customer

You see the stain in the living room, the tidemark on the lintel, the spalled render on the loggia. What you do not see is the path the water takes – which is why patching a sheet of membrane over the stain achieves nothing. Very often it is not a crack in the field of the roof at all, but a detail: parapet, rooflight, roof outlet, a seam that has come apart. We walk the area systematically, and you get every defect.

For you as a business

For property developers, managing agents, industry and local authorities, what counts is that the finding can still be checked afterwards. The report records the methods used, the fields tested and a photograph of every marking, and it places every defect in a roof sketch – so that the roofer works at specific points instead of over the whole area. In a warranty case the same report serves as the basis vis-à-vis the contractor that carried out the work.

How the job runs

1. Settling the build-up. We ask what is on the roof: bituminous membrane or plastic, gravel, green roof, paving slabs, inverted roof. The build-up decides the method.

2. Preparation. The roof area has to be accessible and largely clear. For some methods the area is wetted, for others it has to be dry.

3. Testing. The waterproofing level is examined field by field, with details and penetrations additionally examined individually. Every defect is marked on the membrane, photographed and entered in the sketch.

4. Follow-up check where the method calls for one. After a dye test, the point of emergence inside often only becomes visible after one to four days. We tell you at the first appointment that a second one is needed, and arrange it there and then. Check measurements are charged separately according to time spent and travel.

5. Handover. You receive the report, the sketch and the photographs for the roofer or the sheet-metal roofing contractor. After the repair, a re-check is worthwhile. On request we will gladly carry out the re-check for you – as an appointment of its own, charged according to time spent and travel.

Equipment and methods

Potential difference method (wet method)

The waterproofing membrane is an electrical insulator, while the substrate beneath it is conductive: if the wetted surface is placed under voltage, current flows only where the waterproofing has a hole, and the measuring electrodes show the direction to the defect. In this way every single hole is found, including under ballast, as soon as the test field has been exposed. With metal-faced membranes, a missing conductive substrate or insulation that is already saturated, the method can only be used to a limited extent.

Flood test

A demarcated roof segment is dammed up and the water level observed over a set period; evaporation and rainfall are taken out of the calculation by means of a reference vessel filled at the same time and placed in the test field. If the segment falls behind the reference vessel, it is leaking – the result, however, only says whether a segment is leaking, not at which point, and the structural capacity and the discharge of the water have to be settled beforehand.

Dye test

A dye is added to the water and the suspect area is charged with it. If the dye emerges inside, the water path is proven and not merely assumed; in gravel-covered or planted build-ups the dye is heavily diluted.

The charging is done in levels, from the bottom upwards. We start at floor level; if nothing shows there, the next level up is watered. In doing so we deliberately use several dyes side by side to delimit the areas against one another – at the point of emergence it can then be read off which area carries the water. In this way we work our way up level by level until a result shows.

The method takes time, and not ours but the water’s: the dyed discharge often only shows in the room below after one to four days, because the water first has to find its way through the build-up. On the day of application there is therefore regularly nothing to be seen yet. A dye test consequently includes a follow-up check inside – not as an additional service, but because without the second look the method produces no result. We arrange the check appointment at the first visit. Check measurements are charged separately according to time spent and travel.

Thermography of the roof build-up

Saturated insulation stores heat differently from dry insulation: after sunshine a wet zone cools down more slowly and stands out in the thermal image. The method shows the extent of the wetting, not the hole, and needs a sufficient temperature difference.

Moisture measurement in the room below

Measuring is done above all inside: in the room beneath the roof we go over the traces of the water ingress and record how damp they are. That distinguishes whether an ingress is still fresh or dried out long ago – you cannot tell that from the stain on the ceiling.

Costs and effort

The effort depends on the roof area, the build-up, accessibility and the number of details, which is why we do not state a guide figure; we agree the cost range by telephone before the job.

Where the method needs a follow-up check – with the dye test it is the rule, because the discharge only becomes visible after one to four days – it is part of the scope of work, but is charged as a separate visit according to time spent and travel. We say so before the first appointment, so that it does not first appear on the invoice.

If the damage has been reported to the buildings insurer, the leak detection costs are as a rule covered under trace and access cover; we produce the photographic report so that it can be submitted to the insurer. In a warranty case the same report serves as the basis vis-à-vis the contractor that carried out the work.

Frequently asked questions

Contact and opening hours

CFT Group GmbH, Wiener Straße 99, A-2514 Traiskirchen, +43 (0) 2252 53169 – for Vienna, Lower Austria and Burgenland. We deliberately stay within reach of the site, because a roof appointment depends on short distances, appointments at short notice and local knowledge. Monday to Thursday 8:00–16:30, Friday 8:00–12:00. Outside office hours in writing to office@cft.at, and we will come back to you on the next working day.