Green roof bike pergola & sunken trampoline

[Dave1221]

Hi all

I have recently put in a green roof bike pergola and sunken trampoline.

This was the first gardening job we have done. Feeling reasonably pleased with it. Before when we bought the house there was an ugly 1960s concrete garage with asbestos roof.
We wanted a green roof bike pergola in side return passage and sunken trampoline where the garage was. Our kids cycle lots!

The work involved the following :
1 Sold the old garage on eBay for £1 (they dismantled)
2 Drilled out the concrete base
3 Installed fence (feather edge)
4 Dug the trampoline hole
5 Excavated and installed the (big) posts
6 Built roof and butyle
7 Reused pavers as front path over gravel
8 Need to install trampoline springs and secure bike bars still.

We decided against bike sheds as they were too unwieldy for a side passage.

Questions I would ask contractor next time, probably obvious but new to me:
Ask for a reference
Who exactly is doing the work ? (Employee, you, mate etc)
Who bears the cost for breakages ?
How will you protect the area from rubbish for removal ?
Who pays if the expenses and / or labour is more (or less) than quoted ?

Green roof came in trays sized 30cm square from Wallbarn.

Costs
Materials 2k, labour 2.5k.
Half of the labour was concrete base removal
Sunken trampoline additional £800 cost
Labour day rate here was £110 or £160 skilled
Contractor profit was 1k (they sent their accounts to us by mistake!)

Other things I would do myself
Research more / look out for examples to copy
“Project manage” it myself
Contract only the bits I don’t want to do
Agree measurements formally in writing (not whatsapp)

[Dave1221]

[Dave1221]

[Dave1221]

[Blakeatron]

Did you just rubber the roof and then stick the trays ontop?

[Aluminati]

I have a couple of concerns re the roof install.

The membrane has been stapled to the perimeter, the staples will not last long.

There should be a drip trim moving the water away from the edge. This makes me wonder how the retaining trim has been fixed ?

There should he a drainage stone (20/40 washed pebble) around the perimeter.

Is there a filter layer under the seedum ? Did it come in plastic cassette trays, or just slabs of seedum ?

If you want any sort of longevity out of it, it needs work.

Edited by Aluminati on Tuesday 20th August 08:08

[Dave1221]

Yes. Is that a problem. The truth is that I just let the contractor get on with it. Thinking about it, I will check the supplier instructions. Is there an issue with soil coming out of the trays ?

[57 Chevy]

How on earth did they ever get a car in the garage?

[Aluminati]

Dave1221 said:

Yes. Is that a problem. The truth is that I just let the contractor get on with it. Thinking about it, I will check the supplier instructions. Is there an issue with soil coming out of the trays ?

Yes, it will wash out the seedum root. The whole thing is incorrect. The drainage trim should be fixed with straps of membrane, if it has been held down with the seedum, or screwed down, it won’t be there long.

Not trying to scaremonger, but we do approx 20,000 m2 of seedum yearly, and aware of how fragile they can be if incorrectly installed.

[Dave1221]

Thanks very much Aluminati (and Blakeatron). I really appreciate your thoughts. One of the reasons PH is so great ! I wish I had got you to install it then Aluminati, you sound much more knowledgeable. Where are you located... ?!

57 Chevy, I think cars were smaller in the 60’s!

To comment on the questions/concerns :

- yes it is just trays (not slabs) on top of rubber
- There’s no filter layer. Not sure how exactly this would stop it washing out the seedum root, or have I misunderstood
- not sure about the drip trim but the contractor said they are putting 2cm green treated wood batons around to cover the butyle. Any comments ?
- could add/replace better fixings to staples - should that be done before drip trim ?
- Don’t know how the retaining trim has been fixed (currently away on hol)
- I can probably easily add pebbles (will butt the trays up nearer to the brick wall)

Time is slightly pressing depending on sequencing of the above.

Thanks very much, I owe you a beer if you’re over east Anglia way.

[Aluminati]

You are on the doorstep of Seedum growing central then.

I know ‘It’s only a bike store’ bit again, the proposal of nailing a batten to the perimeter is a bodge.

The water will be constantly running down the posts.

Usually, under 2 degree pitch, you would have filter layer, drainage retention layer, then Seedum.

The Seedum being in cassettes, eases the requirement for the retention layer, but there will be a small hole in the bottom of each pocket in the cassette. If the water passes this hole to quickly, it has a tendency to pull the minimal soil from the pocket, especially if you get heavy rain before the Seeedum has really established.

In a perfect world, you would have a drip trim into a gutter, but again, the view it’s only a bike store may come into play.


Structurally, saturated Seedum can weigh 40-45kg per M2 so looking at the posts/frame, you appear to be ok on that front ( Apart from them being sunk directly into concrete ?)

As it is, it will probably be fine for a few years, but i just get a bit anal when something is not correct, and someone has paid good money for it to be so. Apologies

One completed a few weeks ago.