What Is A Blue Roof? 

I live in New Mexico where they do a Pueblo Style which is a flat roof and they're nothing but expensive headaches. Water weighs 8.3 lb per gallon. The latest thing is to use a rubber membrane but it only takes one pinhole and just like with a condom you're screwed.

Wow I did nt realise I was doing my bit for the environment, all that moss , and weeds plus muck in my gutters are slowing the rain water, keeping the levels down, thanks to people like me the planet is saved......

Hi Roger, I built a large block of flats in central London several years ago. It was designed to have a green roof, all planted with sedum, costing a fortune. Within one week of completion the gulls had pulled up almost every plant leaving it looking like a battle field.

I worked on a very old Spanish flat roof with over a foot of 'loam' on it. Dig down 6" and it would be damp even after a week of hot weather. I think, as the top layers dry out they compact and seal the water in(?) House was always cool in summer and cosy in winter. The walls were stone and about 3' thick.

Seems like the one solid argument for a blue roof - water capture - can be better accomplished with a pitched roof combined with a water retention system

I think I would rather have mandatory soak away tanks put onto the property which then discharge into the main line. Water below ground is far less likely to cause costly damage than holding it above your head. At least then it can be used as grey water for toilets, garden use etc.

Hi Roger... a bit of a blast from the past for me.. back in the mid 1970s. fresh out of C-J apprenticeship and being a bit of a self confessed no-it-all, I somehow landed a job as assistant works (buildings) manager with a regional Co- Op, talk about going back in time even in those days the Co op had sadly missed the boat in sales and buildings . My patch covered mostly rural east Anglia where I discovered numerous flat roof leaks.....a construction I just didn't understand, usually on outbuildings for milk storage made up of timber joist- corrugated asbestos- sand-sawn timber boards-hessian and a type of asphalt with a galvanised 3" up-stand edge trim allowing the final topping to be similar to a mixed ballast. It gave me a few problems along poorly maintained buildings in need of constant repair with a very limited budget didn't take me long to reconsider my future career in construction.......I made my escape. thank you for the reminder. ... ............keep the 'rants' coming and thanks

I've had enough trouble with my flat roof leaking. Last thing I want to do is store water on it!

Roof... hold water... what can go wrong!

Thanks for the information Rodger great update I can see more jobs coming our way to replace these over next few years. Will be a shame to see the customers disheartened when they fail. I hope they see this video if they are suggested before making their decision as this will be a big fail.

The argument about alleviating flood risks doesn't really hold water (see what I did there?) as, other than for flash storm events, the runoff is just delayed for a bit. Far more likely is persistent precipitation where this will have minimal impact.

Best channel ever I’ve learned so much from you guys

Awesome video Rodger, thank you

Very interesting point you raise about the evaporation rate and is absolutely right. When the water evaporates, you're going to lose a lot of that insulation that keeps the building cool. The best way to insulate the building will always be with actual insulation such as PIR or Rockwool. It's the same when people say the green roof can be part of the attenuation - to a point it can as it can soak up rainwater run-off in the substrate and feed it back into the environment via transpiration. However, there is no way of calculating exactly how much it's going to attenuate, hence you would specify the blue roof attenuation cells with reduced outlet over a green roof for a proper attenuation solution. One thing that they are very good with - saturated or dry - is keeping the roof cool and not radiating heat back into the atmosphere. The difference between a green roof and a standard flat bitumen roof is about 40 degrees Celsius. Good way to test it - stand in the garden bare foot if we get another 40 degree heat wave this summer, go and stand on the paving slabs and then stand on the grass, you will see a huge difference! It's called Urban Heat Island Effect. The World Wildlife Federation put a research video together on this topic a little while ago where they did a case study on New York City. They reckon 1 billion square meters of New York is all flat roof space. They made a claim that if all of these roof areas were green roofs, it could actually lower the cities core temperature by 2 degrees Celsius, which in the fight against climate change is very good! It's also good with solar panels - look at Bauder's biosolar solution. Where the green roof keeps the roof cooler, it actually makes the solar panels more efficient as they work better in cool environments! Also, any condensation that develops on the PVs can drip and feed back into the green roof system.

New York City used to do huge collection tanks on their roofs. That was used for grey water purposes and in some places for flushing toilets. Don’t know if they still do it. They had the same hardscape ground level flooding issues as other major cities and the water tanks helped a lot.

I think the concept of blue roofs is very exciting, and holds much potential. Slowing down the water flow is smart with heavy rainfall becomming more common.

If they can solve it, having a flat roof with greenery could be a winner. It's not without cost, pain and lots of trial & error. Better water retention, better looking at a green roof than not, maybe combined with a solar canopy for more utility. Probably drought tolerant grasses would be a good starter but eventually nature (bird poo seeds) will figure out what grows there and what doesn't.

Perfect timing YET AGAIN!! We are getting a green roof and they said we should get a blue roof under the green roof! I basically thought “Ahh, can’t be difficult. Probably just a few membranes, I’ll wack it together myself on the day of install”… now I’m thinking twice! That said the bit we are doing is a fibreglass flat roof, which is well made and I think zero chance of leaks… it has massive fibreglass upstands of about 300mm or more and a reasonable fall, with integrated gulley that drops through the bottom of the roof into an overhang which is actually outside … (not in the building!)

Thanks for lovely video

can't wait for the first cold weather and following thaw!!!

I have got a yellow roof Rog, I put some massive gutters on and filled them with car sponges, planet saved, job done!

Why not just put a water butt in the downspouts with a trickle out put into the existing drain, or a soak-away?

Like most of the other comments - seems like the roof is the worst place to store water before allowing it to trickle into drainage. But WhaDoIKnow :)

Hope they remember to check they don’t overload the roof. Wet soil weighs a ton compèred with dry soil.

Grand Design’s has a lot to answer to. The 🐑 on a Thursday (whenever it’s on.) sipping their G&T’s go “that looks good, the members at the tennis club will be so jealous.” Find out who can do it for the cheapest. 😂

Thought you were going to say Red..row at the end, was waiting for a quality related dig with the light flickering or something! Interesting topic to raise, I'm trying not to be a pessimist but I can't help think it's not for our variable climate (freezing temps and expansion for instance?). Other than watertightness, I can see the average Structural Engineer not enjoying the calcs needed. I guess it'll be easier/cheaper and more sustainable for everyone to have a soakaway/waterbutt if they're not in clay, but may be in tough planning applications they could pull this one out of their...hats. Nice work Roger/Dylan 👍

I know it wouldn't work everywhere, but having very large planters running length of building at ground level would surely make more sense? Rather than vegetation and storage on the roof, just have it at ground level with drains routed there?

I remember the Grand Designs where they had a 'wet roof'. They brought in German 'specialist' contractors, as British contractors couldn't do it... It still leaked. 🤣

I saw a Grand Designs on a house in Hackney which was managed by a pair of arrogant German architects, who were at pains to slag off the British builders at every opportunity. They got a roofing specialist in from Germany and they designed the roof to hold water, I got the impression that this was the way it was done in Germany, apparently it helps protect the felt. Needless to say the roof leaked and had to be re done, with a fall, by a British roofer, because the Germans refused to travel back to put it right. Lol.

Then there's the extra strengthening involved due to the extra weight, not to mention the health hazard created through standing water going rancid, legionella and other undesirables, etc. What a load of crap, but interesting video. Got any more. Wouldn't mind seeing a vid on installing photovoltaic panel system on a pitched roof, 😁

I'm from Taiwan, a rainy country. It's the first time for me to hear about blue roof.

Many years ago i use to live in Burnt Oak, Middlesex, when "all" the houses in my road had front gardens & privet hedges, which captured rain water. Nowadays not a garden/privet hedge to be seen as instead all hardstanding/block paved for parking, so naturally rainwater has nowhere to go other than down the drains. Clearly Blue Roofs is yet another building industry fad disaster waiting to happen, with stagnant water risk and associated Legionella Risk Assessors all over the place 😨

I have been building blue roofs for last 30 years, I try and tell my customers they are blue roofs, they just complain and say my flat roof is 'ponding.

Although it might be considered new tech the reality is much older buildings with insufficient outlets to carry rainfall will act in the same way during the peak of a storm. Roofs should be laid to falls (greater than 2.5%) so after rainfall water will drain away. Personal view is the blueroof approach would work if the roof deck is concrete and you have the structural capacity to lay screed to falls to the outlets. The outlets are then restricted but with an overflow so excess water can be removed if there is two storms in succession. Post storm as the roof has falls the water would drain away. Typically I've only seen blueroofs used in situations where space for buried or above ground tanks is not possible. It has its place in attenuation solutions but isn't the solution for every project. A lot of roof types are also unsuitable for the technology.

Question what is best material for a Flat Roof Terrace .?

In a hot country could you replenish the water layer from artesian source. Choice of soil/plant/top gravel layer must be key to retaining the moisture. You could do a SUDs video sometime. Enforcement seems hit and miss and do new developers implement (I don't recall SUDs block paving on many of the new housing estates. Do they all run off into soakaways?

I do firmly believe we should be collecting and reusing more rainwater, flushing toilets, washing pots, washing cars and garden watering etc , but this seems like a very risky way of doing it, changing and unpredictable load on the walls and joists, plus the risk of leaks etc. Grey water storage tanks underground seem like a much better idea.

What's the weight of a blue roof and what structure below supports that weight? I would guess it needs a concrete flat roof as in an apartment block (or the top deck of a multi-storey car park). Could standard wooden joists hold it up? The triangular cross-section of a pitched roof gives a strong, solid base for the weight of tiles, but a flat roof doesn't have that structural advantage. Great video because I had never heard of this, so thanks to ranting Roger! Professional Builder magazine was never as interesting as the videos.

I have done 'blue roofs' for about 20 years without any issues on all my ground floor extensions and I never called them blue roof but green roof. It's brilliant system for enhancing biodiversity and making sure it stays fresh in the summer. There is no magic or high-tech part to it. All you need is a good flexible roofing membrane that laps up nicely to the sides under your copings. Keep a gravelled border on the perimeter to keep weeds growing in your outside walls.

every blue roof iv seen 2! have had some kind of issue . wouldn't it make more sense to have a water storage tank and then use the water later to water the garden say like in the summer? on a tall building you could get quite a head of pressure and reduce the flow by sticking a generator in the main out flow and feed the energy into the grid. or just have a soak away where you can. its the same area.

The posh version of that is a rooftop pool and that exists. I think it‘s possible if you build it like a pool. I would not want to bet on a plastic membrane or something like that. Stainless steel sheets welded together should do the job.

Germany seem to have a lot of these type of roofs? Don't new housing estates have to build large ponds to reduce the surge which is part of this SUDS?

how about as an idea on blocks of flats to collect the rainwater to use for toilet flushing, in cities even in the UK there are sometimes water shortages

We're contemplating a green/living roof for our extension. Any thoughts on them would be appreciated..

I think that blue roofs could be really game changing in the bigger cities like New York because it can prevent inundation in The streets.

Not to mention the structure will require additional strength to account for the increased roof loading 6" thick what's that approx 45lbs a square yard, in water. 🤣🤣🤣🤣

Wife: ‘’Darling, where are you going’’ Husband: ‘’I’m just popping out to the roof to get some dinner’’

Surely in winter in this country the roof will almost always be full to the overflow and any more rain falling will run off at the same rate as any other roof with the same surface area?

By the way, it’s not true that blue roofs are only being done by grand projects. I’m buying a green roof for about 1k and the guys said they could provide blue roof build up for only a hundred more for me to install myself…

I like your videos and learn a lot from a lot of them, so please don't think me a smart backside, but I think flat roofs *were* a problem until not may years ago when EPDM synthetic rubber roofs became widely available. I used to be a Firestone EPDM contractor - couldn't fault the product and never ever had any issue with it - we did it all to spec. and properly and with love and care - as it worked so well and helped customers out who had tried everything out and all else had failed. It will withstand a head pressure of several metres, so one can build vast water tanks out of it. It's eco friendly, too. Also, when water evaporates, it does bring about a cooling effect, so if it evaporates faster, it cools faster, better if it happens gently for a slow cooling effect for most purposes, and that can be achieved using plants, peat and all manner of methods. I suspect that water will become such an issue soon that people will need to collect rainwater to use for themselves (energy blackouts or brownouts = no mains water, no treatment plants running, no chemicals to treat water), so it's not a bad idea, but the structure will have to be darned solid to support that weight and designed to withstand ice expansion etc, too. Cheers.

All I have to say about that is 'sod that for a game of soldiers!' Asking for trouble!

The latest fad I am seeing more and more is bunded housing estates. They have a massive grassed storage bund or two somewhere on the development that rainwater feeds into to prevent drain surge.

Hi Roger , just a quick question -----have you presented a Party Wall topic ?

I didn't realise you had done a blue roof video. CIRIA are in the process of publishing a set of guidance / code of practice for blue roofs, which the industry is desperately lacking in. At present there are numerous interpretations of how a blue roof should function and some terrible 3rd-party products on the market without any form of testing / certification. Fortunately things are improving. One fundamental change is the time-to-half-empty which has changed from 12 hours to 24 (therefore fully drained within 48 hours). This makes blue roofs more viable, particularly on podium structures and large roofs. One common misconception is that the attenuated water is exposed - this should never be the case, it will always be within the build up and beneath the surface finishes. Once complete, it should function as a normal flat roof in that for the majority of the time it contains no standing water.

If we want to reduce run off have holding tank in the ground so you catch water and use it water you garden wash the car etc

Pond liner , ontop of a grp flat roof. Some koi fish, and Job done.

wno is here beacus maui hawaii ?

Get a couple of Carp and you can sit on the chimney with your fishing rod

I worked for Cadbury's 55 years ago at one of their warehouses and they had one of those type of flat roofs and it was filled with 12" deep of water and the idea was to keep the chocolate cool in the warm weather , so I know its NOT a new idea.

Never mind the additional load of all that standing water on the roofing structure. Then wait until winter when that purposefully designed roof ponding freezes and applies preasure on the containment. Rinse & repeat year after year and that whole system won't last long.

Swans,ducks,seagulls would love this...

In a temperate climate like ours, wouldn't a blue roof act to keep the house warm, as the water wouldn't evaporate so readily?

Basically the councils waterways don't want to clean the sewers and clean up the river beds too simple

Surely a normal underground soakaway would do a better job, for a lot less money and a lot less risk?

Green roof seems great idea. Should have standards in place first though.

Hi Roger, I am a civil engineer, I spec blue roofs all the time. Get me on, I will dispel the myths for you. Look forward to hearing from you.

Evaporation causes cooling so it would cool in a tropical situation.

The same people who are willing to spend a fortune to hold rain on the roof and ease the flow into the sewers are happily turning any bit of open ground into a paved car park! The rain which used to soak into the ground is now sent to the sewers. Foot, shoot, self springs to mind!

Hey Roger ... I have the perfect Merch' for these Folks with a Great QUOTE on it .... "I've Joined 'The Emperors New Clothes' Society" .... Seems pretty appropriate to Me 🤣😂😅 .... #CheckFred EH ??? 😀

It's the solar roadways of roofs, isn't it? A million options for capturing or draining water at ground level, but we can sell you this new thing called a blue roof. It's clearly bollocks, outside of a few niche applications. Expect to see it everywhere soon. Extravagant building won't solve climate change.

I would have thought that the answer was when a building contractor submits plans to build a new development that they have to pay for the drainage infrastructure to be upgraded to cope. But I suspect that it's a case of cross the right palms with silver build it and then it's someone else's problem.

And when it freezes, bang goes your membrane and the rice crop !

4:55 “Redruth” that’s in Cornwall.

I see the downsides and I think there will need to be a lot of development to make blue roofs good. For example you need to have a guarantee in case water leaks into the building. But I think blue roofs are here to stay.

Hi Roger is Skillbuilder having any luck in finding a replacement for James yet?

I've hit the blue ceiling When I opened the 'Anne Summers' box my misses had ordered

Errrr I think rain water storage systems is much easier overall, as they already are in use, without the hassle of a small swimming pool sitting above your head all the time...

Is it like a blue movie?

Install water tanks, in case of heavy storm, empty tanks beforehand

What about the grass roofs that have been done for centuries. Aren't they a type of blue roof?

Is it awt like a blue waffle

Sounds like flooding in the walls to me. Which sounds like mold. Which sounds like respiratory damage.

called a blue roof because of all the swearing you get when it leaks. "They" need to start making the roads and pavements more water permeable., also down pipes should go into the ground perhaps via soakaways rather than down drains.

Well Roger. But call me old fashioned bit storng water on a flat roof is only leading to one result leaks , trying to make sure the contractors ie carpenters roofers do it properly not to mention if it starts to leak goodbye timbers even when it's a bit of drizzle ? Look like another in 20 years people saying why the he'll did they fo that ? I'd worry about drives replacing grass than this for water saturation mate ? All the best and stay safe 👍

Oh dear!

Stupid idea. Entire roof would have to be one single continuous membrane with no seams or penetrations whatsoever for it to be reliable. Got pipes? Better reroute those bad boys out the side of the building along with whatever ventilation your old roof had, because those are no longer going to function without water getting in. Most manufacturers(epdm, tpo, pvc, etc.) state that ponding water(which isn’t good) is acceptable as long as it evaporates within 48 hours. Well, that ain’t happening here. So they want to come in and completely change the way things are done, do they? If I were them, I’d have some regulations put in place before I market any product related to blue roofing.

Like you say...disaster waiting to happen. Not to mention the significant added weight on the structure.

Seems a water (but t) or (but ts) with a slow 🐌 drainage system would be less problematic. Somebody said they thought we'd reached peak stupidity, I think we're getting there. The censoring algorithm thinks 🤔 the human bottom is being referenced here!

Maybe you build a normal roof and then install a tank for this on top. Then when the tank fails, you still have a normal roof to catch the leaks.

Few slow draining water butts would be cheaper and safer

I think its a good idea IF you live in a area which is prone to flooding ( which were getting more and more), but it should really be made from architects designn and solid (like poured cement ect). Otherwise dodgie

Old idea,years ago the outlets were put higher to retain water to keep the roof cool not the best of ideas ,as for an asphalt roof you’ll not get better as a flat roof with longevity installed by a pro ,much better than the I’ve learned GRP down at selco mob 😉

Sounds like blue roof will eventually change into water shortage change into price hike of water. Like electric car eventually equalled higher electricity prices 🤔

Stop the concrete being poured on drives to make stone effect patterns.

Its only a disaster because we (The British) will not work/complete buildings/construction projects to the required standards/Quality in order to be successful. Take flats roofs as an example, there are plenty of countries in Europe who can build flat roofs that do not leak so it should not be unreasonable to suggest that will should also be able to do it. Now as an Engineer, I fully agree that it would be better if we do not build flat roofs unless we have to and I think the same can be said for "blue roofs" I am sure there are/is better ways to retain water in the actual ground. How about not building on or near flood planes and perhaps adding or allowing marshy land to form naturally or would this create too much of a dent into the new home-builders market?

The roof is not a good place to store water. Big water tanks on the ground is way more safe and easier to construct.

Instead of a blue roof how about a brown floor. ie, stop building over every square inch of land and leave some soil so then you won't get all this 'run off' problem. (and also how about cleaning the bloody drains out!)

How to make a small leak a mammoth of a job.

Bunch of British builders in the comments mocking modern insulation techniques sounds peculiar. Something about the kettle and the pot.

So if we all end up with blue roofs won't we still just get all the runoff at once, only 24hrs later? 🤔