A sedum green roof is one of the easiest ways to get more green into a small garden. It turns a plain shed, bike store or log store into a living patch of colour that changes with the seasons, and it gives the bees somewhere to feed. Here's how we put one on, and how you can do the same.
Can your building take a sedum green roof?
Most garden buildings can, as long as the structure is strong enough. A green roof is heavier than felt, especially when it's wet. A sturdy timber store or shed with a solid roof deck is usually fine, but if you're not sure, ask a builder to check it first. There are two other things to look at:
- The pitch. Sedum trays suit flat and gently sloping roofs. A steeper roof needs edge restraints to stop the trays sliding, so get in touch and we'll advise.
- The waterproofing. The roof has to be watertight already. A green roof sits on top of a sound waterproof layer, such as felt or EPDM rubber. It doesn't replace it.
What you'll need
- Green roof fleece, which protects the waterproof layer and holds a little moisture
- A drainage layer, so excess rain runs off and the roots never sit in water
- Pre-grown sedum trays. The ones we use are 50cm by 50cm and slot together into one continuous blanket of sedum
- Decorative stone for a neat, free-draining edge (optional)
- A timber upstand or edging batten around the roof to hold it all in place
You don't have to source all of this yourself. We make sedum green roofs to measure for garden buildings in Lincolnshire, so if you'd like us to supply and fit yours, tell us about your roof.
Step by step
1. Prepare the roof
Sweep the roof clean and look for anything sharp, like nails or screw heads, that could puncture the waterproofing. If there's no timber upstand round the edge, fix one, and leave a gap or outlet so water can drain away.
2. Lay the fleece
Roll the fleece out across the whole roof. Overlap the joins by about 10cm and take it a little way up the inside of the edging.
3. Add the drainage layer
Lay the drainage layer on top of the fleece with the edges butted together, so there are no gaps.
4. Place the sedum trays
Start at the lowest edge and work up the roof, pushing each tray tight against the last. Where you need to fit round corners, trim the trays with a sharp knife or a saw.
5. Finish the edges
Fill the gap between the trays and the edging with decorative stone. It looks tidy. More usefully, the stone protects the edges from wind and keeps the drainage outlets clear.
6. Water it in
Give the new roof a good soak. For the first few weeks, while the roots settle, water it whenever there's a dry spell.
Looking after a sedum roof
Once it's established, a sedum roof needs very little from you:
- In the first year, water only during long dry spells. After that it gets through most British summers on its own.
- Pull out weeds and tree seedlings once or twice a year.
- If growth looks thin, give it a light feed of slow-release fertiliser in spring.
- Keep drainage outlets and gutters clear of fallen leaves.
Sedum changes colour through the year. It's fresh green in spring and flowers in summer, then often turns red or bronze in winter or during a drought. That's normal. It doesn't mean the roof is dying.
When's the best time to install a green roof?
Spring and early autumn are best. The weather's mild and the rain helps the roots get going. Don't lay a green roof during a heatwave or when the ground is frozen.
Or we can do it for you
Every bike store, log store, bin store and carport we build in our Metheringham workshop can have a living sedum roof, grown on our own farm in Lincolnshire. Have a look at our garden storage and made-to-measure green roofs, or get in touch about your roof and we'll help you measure up. Green roofs start from £45 per square metre, and we deliver and install them in Lincolnshire only.
