Yes, polyurea is one of the best solutions for waterproofing a flat roof. The coating is applied seamlessly across the entire roof, including around roof penetrations, upstands and corners, exactly the places where leaks usually begin.
Because polyurea bonds fully to the substrate and has no loose seams or overlaps, water cannot get in anywhere. The layer is also elastic and effortlessly absorbs the roof's expansion and contraction caused by temperature changes.
Polyurea is suitable for both renovating existing roofs and new construction, and can often be applied over the existing roof covering after proper preparation.
The build-up on a roof is fixed. First a primer matched to the substrate, since concrete, tiles, bitumen, timber and an existing cured coating each call for a different primer and a different consumption. The sprayed membrane goes on top of that, around 2.5 kilos per square metre on a flat roof.
A UV top layer is always needed on a roof, even if you never walk on it. Old EPDM or PVC sheeting and gravel ballast have to come off completely first.
What has to happen underneath the coating
The layer itself is only half the story. What sits beneath it decides whether it lasts twenty years or lets go after two. Every substrate needs its own preparation.
Concrete and mortar are mechanically roughened and made dust free, after which an epoxy bonding primer goes on. Existing tiles or natural stone take a different epoxy primer, because a smooth surface offers less grip.
If there is still bitumen on the roof that is firmly attached and dry, the coating can go straight over it with a water based bonding primer. That saves demolition, disposal costs and days of work. Loose, blistering or wet areas do have to come off.
Gravel always has to go completely, as do old EPDM or PVC membranes. Those lie loose on the roof rather than bonded to it, so there is nothing to adhere to.
Seams are the weak point, and there are none
Look at a roof that leaks and you almost never end up in the middle of a field. It starts at an upstand, at a roof penetration, around a chimney, at a rainwater outlet, or where two sheets overlap.
With sheet membranes every junction is handwork and therefore a potential weak point. A sprayed layer does not have those junctions: it runs across the field, up the upstand and around the penetration in one movement.
When surveying we therefore look mainly at the details. How many linear metres of roof edge and upstand there are, how many penetrations sit in the roof and how the outlets are finished often decides the work more than the square metres do.
Moisture in the structure is where it really goes wrong
The biggest mistake in a roof renovation is applying a waterproof layer over a structure that is still wet. The moisture can no longer escape and builds vapour pressure as soon as the sun hits it. The result is blistering under the coating.
That is why we measure the moisture content of the substrate beforehand, rather than only checking whether it feels dry. If the insulation under the roof is soaked, no coating will help: that insulation has to come out first.
It is also why we prefer not to inspect a roof the day after rain. A roof that looks dry can be in a very different state further down.
Falls and drainage decide how long it stays looking good
A coating makes a roof watertight, but it does not correct poor falls. If a puddle stands there after rain, it will still stand there after the renovation.
Standing water is not a problem for the waterproofing, but it attracts dirt and algae and leaves tide marks. On a roof you look out over from a window, that is worth discussing beforehand.
Where the falls genuinely fall short, a levelling layer can be applied before spraying to restore the slope. That is extra work, so it belongs in the quotation rather than appearing afterwards.
Can it go on a pitched roof
Yes. The layer is sprayed and cures within minutes, so it does not run on a slope. We have done pitched roofs where the old bitumen shingles had partly blown away.
The appearance does change. Where there was a texture of shingles or tiles you get a smooth, even layer in the colour you choose. For one house that is exactly the point, for another it is not. So always ask for photographs of earlier work before you decide.
On a pitched roof access weighs more heavily. Scaffolding or a cherry picker and the height of the building then account for a large part of the price, and that belongs in the quotation as a separate item.
How long it takes and when it can be done
An average flat roof is finished in a few days, of which the spraying itself often takes only one. Most of the work is preparation: cleaning, roughening, masking, repairing and priming.
The layer is rain resistant within minutes, so an unexpected shower at the end of the day is not a disaster. The UV top coat needs longer to cure fully.
On the Costa Blanca work can go on for most of the year. What stops the job is not cold but moisture: early morning dew, a damp substrate or high humidity. In summer we therefore often start early and pause through the afternoon heat.
What else you get out of it
A light colour on the roof reflects a large share of the solar radiation. In a Spanish summer that makes a noticeable difference to the temperature of the space below, and therefore to how hard your air conditioning has to work.
The weight is low compared with a new layer of concrete or tiles, so the structure gains very little. And because nothing is torched, there is no open flame on your roof during the work.
Expected service life of the system is fifteen to twenty five years, depending on the substrate, maintenance and loading. On the waterproofing we give a ten year guarantee.
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