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Covering an EPDM roof with pebbles


chrisk

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Hi

We have a single ply EPDM flat roof extension containing 2 bedrooms. We knew that choosing a flat roof instead of pitched tiles would mean increased noise during rainfall, but it's pretty loud and distracting during bad weather. Wind blown water on the roof is particularly noisy, so I've been thinking of ways to provide a layer of protection.

The roof was built to carry the weight of sedum trays, which can hit 90kg per sqm when fully saturated. Our structural engineer said there may be some slight deflection if loading it to that degree, and we may get small hairline cracks in the ceilings. The option of sedum trays is therefore not filling me with enthusiasm! The cost of sedum is also quite prohibitive, with quotes for our 55sqm roof coming in around £2500.

The other option I've been investigating is white pebbles. I can't imagine that they could be laid direct on the EPDM as they would damage it, so my plan is to use driveway gravel grids sitting on Wallbarn rubber paving support pads, to primarily give a layer of separation from the EPDM but also so that there are no obstructions underneath as rainwater still needs to run off the original pitched roof. We'd also get improved insulation during hot weather, and hopefully extend the life of the EPDM too.

Does this sound appropriate? I'd really welcome your thoughts.

Thanks in advance

Edited by chrisk
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5 minutes ago, chrisk said:

white pebbles

Very retro. roofing felt used to have stone either in it or sprinkled on top for durability and heat reflection.

It works, but it also collects dirt and may need cleaning occasionally.

 

I agree re sedum. it only converts CO2 to plant once, after which it lives and dies. also you will be importing it from far away.

I don't like that planners place sedum above harvesting and lagoons in the hierarchy of sustainable design. But rhen they dont undestand the impolications, and have fallen for the hype.

When explained, I find that they accept changes.

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Another thought. the spec for a sedum roof should have had a very special roof covering that resists the roots. However it is not UV resistant, so be careful to see the whole design through if you make changes.

A tray of stone will be very heavy, and get heavier as it fills with muck and then weeds. Just spread light covered gravel.....or leave it bare and do something better with the water.

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@saveasteading 

Another thought. the spec for a sedum roof should have had a very special roof coveringthat resists the roots. However it is not UV resistant, so be careful to see the whole designthrough if you make changes.

That’s very good point.

Edited by markc
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Need to select your slabs carefully, and check it.

 

Pressed Council Slabs come in at 120kg per sqm.

 

I wonder about river pebbles rather than gravel, and see if they can be cleaned with a pressure washer. Buy one or two bags for a trial.

 

If they are going to get dust and lichen on, then buy the colour they are going to turn - NOT white.

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20 hours ago, Ferdinand said:

I wonder about river pebbles rather than gravel, and see if they can be cleaned with a pressure washer. Buy one or two bags for a trial.

 

If they are going to get dust and lichen on, then buy the colour they are going to turn - NOT white.

You're right, white is probably not a sensible choice of colour. They would only be white once - when initially laid.

Porcelain titles on upstands would certainly do the job but would be more costly than gravel grids and pebbles, can't find anything much under £14 per sqm.

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22 minutes ago, saveasteading said:

Back to basics.  If this is only to stop the splashing noise then tiles are not the answer.
What is causing the noise? Rain falling from another roof or gutter?

 

Is it also for appearance.

The flat roof runs the entire length of our bungalow and the rainwater from half of the existing tiled roof, which faces west, runs off onto it. When we have heavy rain and strong winds, the noise of sloshing water is very noticeable, and can wake us up. Rainfall can also be quite loud too. Having a suitable protective layer would stop that, extend the life of the EPDM and reduce temperatures in summer. Basically I'm looking for a cheaper, lighter alternative to sedum trays. We can't see the flat roof so there are no concerns over appearance.

Edited by chrisk
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1 minute ago, chrisk said:

The flat roof runs the entire length of our bungalow and the rainwater from half of the existing tiled roof, which faces west, runs off onto it. When we have heavy rain and strong winds, the noise of sloshing water is very noticeable, and can wake us up. Rainfall can also be quite loud too. Having a suitable protective layer would stop that, extend the life of the EPDM and reduce temperatures in summer. Basically I'm looking for a cheaper, lighter alternative to sedum trays.

 

I'm having a associational morning. 

 

You reminded me of this. And "Chrisk" reminded me of "Tomsk", the womble. Suspect Tomsk was kidnapped by @Onoff decades ago, and is still trying to catch up.

 

 

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13 minutes ago, saveasteading said:

falls onto it direct from the roof, or via a gutter and downpipe?

Direct from the roof. The flat roof is snug up against the bottom row of tiles.

 

When it's proper heavy rain it's like the Orinoco up there. Sorry, couldn't resist

Edited by chrisk
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So I would resist the big pebbles thing. They will slow the flow and back it up against the wall and the awkward junction you are making.

 

Are you sure there will be  a noise when you have built this? Or is it already mostly built?

 

I am ever more confused about what you have . sketch or photo please?

 

If the new roof  is snug to the main roof tiles, it can't be falling far and shouldn't be much splashing or noise.

 

if snug, how would you fit a thickish layer of sedum or other material.

 

How about a nice gutter to catch the water and a couple of pipes that shoot the rain smoothly and silently in the right direction.?

This is what people usually do and it works.

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31 minutes ago, saveasteading said:

So I would resist the big pebbles thing. They will slow the flow and back it up against the wall and the awkward junction you are making.

 

Are you sure there will be  a noise when you have built this? Or is it already mostly built?

 

I am ever more confused about what you have . sketch or photo please?

 

If the new roof  is snug to the main roof tiles, it can't be falling far and shouldn't be much splashing or noise.

 

if snug, how would you fit a thickish layer of sedum or other material.

 

How about a nice gutter to catch the water and a couple of pipes that shoot the rain smoothly and silently in the right direction.?

This is what people usually do and it works.

The roof was finished 18 months ago, see the picture. It's totally snug to the tiles, the noise comes from a) heavy rain falling directly on the flat roof and b) water being blown around in strong winds. I have thought of adding a gutter to catch the water off the tiled roof, but can't come up with anything workable because there's no room below the tiles, so I need the flat roof to continue to take the run-off.

 

My pebble idea involved using driveway gravel grids raised up on rubber support pads, so water could flow freely underneath.

 

flatroof.jpg

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That is really helpful.

except I am still surprised that there is much noise from the roof flow , unless the new roof is very light weight and has little sound absorption.

 

I can't see that you have any height for a new surface. Anything you build will need a gap between it and the existing wall and may create big build-ups and problems.

 

One suggestion and then I give up. Have a gutter made specially that tucks under the tiles. then slopes out to the front at about 45degrees, and then to flat. or a curve. this would catch the  flow quietly and guide it onto the flat roof.

 

As I said earlier check the spec of the membrane. If it was specified for sedum then it isn't any good in daylight. Your architect and builder should have allowed for one or the other.

that also creates an issue near the edge as the membrane has to change where the sedum stops.

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For the benefit of all. As stated above I think sedum is overrated. 

In case you ever want to get rid of it from a planner's request, or architect's whim I recall the following, after a summary.

 

it is good for hiding roofs in the countryside, and for keeping roofs cool in summer, if watered.

 

BUT

the sedum and plastic crates have to be transported from somewhere.

the roof has to be reinforced, and I once calculated that the material use was more carbon than the sedum would ever save.

any rain stuck in the sedum doesn't reach a rainwater harvester.

it needs maintenance, to remove dead stuff and replace...h and s

needs weeding.... h and s 

the membrane issue as above

 

I once had it specified on a job designed by a 'planning only' architect.

whether the planners asked for it or it was for fun I don't know. client hadn't understood what it was and said they would rather not have it, for maintenance and for capital cost.

I mentioned to the planner that it was worse than useless and dangerous , but i would have to resubmit planning.

I briefly thought of writing 'sedum' on the flat roof, as  the word on the plan was the only refence.

 

Useful for the future though was a visit be HSE. the inspector was on a spot visit, which coincided with me being ion site. I explained the sedum, and the need to access it. dreadful idea he said. 'can you instruct us to delete it then? No, i haven't the authority.

BUT I can ask you to leave a gap to the perimeter so that ladder access is safer, and there is a hard surface to step onto. 

so that saved 20% of it, and made it easier to build.

And that is when we learnt about changing the material where under sedum or exposed.

In future I can quote the safety issue  and refuse to include it, and instead have something else.

 

Any questions?

 

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