2013 DIY Green-roofed Extension Build
Discussion
Long time lurker on this forum (and pistonheads generally) thought I would finally get around to writing up a bit of a blog as to what I have been up to most of last summer/autumn.
My partner and I are both architecture students, and unlike alot of our coursemates, are actually pretty interested in the hands-on/practical side of construction.
A family member has wanted a small extension for quite a while, so we decided to take a year out from uni and do as much of the design and construction ourselves as possible.
So this is the house. A late 50s/ early 60s house in Surrey. Fairly standard for its age, and typically has already had quite a few extensions in the past. The house isn't wanting for more space, but as the house has grown and expanded around the core, the kitchen has ended up far too small, and the current layout on the groundfloor doesn't really work, and can't be significantly improved without a little extension to square off the back.
Existing Layout - cramped kitchen with too many doors cutting up the potenial worktop space
Proposed- Much larger kitchen, making better use of the available space, and moving the kitchen-diner to enjoy the view and light of the garden to the south
The extension is 11.5m2, so not exactly huge, but as can be seen from the plans, opens up a huge number of options for the groundfloor layout, including a much bigger kitchen, with a 5m clear run of worktop down one side, compared to the old kitchen, which has about 2m of worktop in total!
After accurately surveying the house, we knocked up a few sketchup models of our thoughts, to agree on a finish/style and sorted out the relevant planning other issues, such as a build over agreement for the sewer running across the back of the house where the extension was proposed.
As you can see, its a fairly typical extension, its south facing, so velux windows and folding sliding doors should allow the most light in, but we designed the roof overhang to protect from overheating during the summer, when the sun is higher in the sky. Wall construction brickwork to match existing.
However, following some really interesting lectures at uni, we wanted to have some fun with the roof, the house sits opposite some really lovely woodland and the house has a really nice mature garden, so we wanted to reflect that in the design somehow, and also wanted to experiment with a green roof!
The plan, even early on was for a extensive green roof with a good few inches of soil, allowing a variety of plans to be grown up there.
It also gave us a chance to try out a really lovely roof edge detail, and the drainage of the roof allows us to avoid putting up guttering, so it gives a really clean edge, and even in the renders were we all excited enough with it to commit, and think about getting ready to build it!!
So if there is any interest, I can carry on through the rest of the design/ build stages!?
My partner and I are both architecture students, and unlike alot of our coursemates, are actually pretty interested in the hands-on/practical side of construction.
A family member has wanted a small extension for quite a while, so we decided to take a year out from uni and do as much of the design and construction ourselves as possible.
So this is the house. A late 50s/ early 60s house in Surrey. Fairly standard for its age, and typically has already had quite a few extensions in the past. The house isn't wanting for more space, but as the house has grown and expanded around the core, the kitchen has ended up far too small, and the current layout on the groundfloor doesn't really work, and can't be significantly improved without a little extension to square off the back.
Existing Layout - cramped kitchen with too many doors cutting up the potenial worktop space
Proposed- Much larger kitchen, making better use of the available space, and moving the kitchen-diner to enjoy the view and light of the garden to the south
The extension is 11.5m2, so not exactly huge, but as can be seen from the plans, opens up a huge number of options for the groundfloor layout, including a much bigger kitchen, with a 5m clear run of worktop down one side, compared to the old kitchen, which has about 2m of worktop in total!
After accurately surveying the house, we knocked up a few sketchup models of our thoughts, to agree on a finish/style and sorted out the relevant planning other issues, such as a build over agreement for the sewer running across the back of the house where the extension was proposed.
As you can see, its a fairly typical extension, its south facing, so velux windows and folding sliding doors should allow the most light in, but we designed the roof overhang to protect from overheating during the summer, when the sun is higher in the sky. Wall construction brickwork to match existing.
However, following some really interesting lectures at uni, we wanted to have some fun with the roof, the house sits opposite some really lovely woodland and the house has a really nice mature garden, so we wanted to reflect that in the design somehow, and also wanted to experiment with a green roof!
The plan, even early on was for a extensive green roof with a good few inches of soil, allowing a variety of plans to be grown up there.
It also gave us a chance to try out a really lovely roof edge detail, and the drainage of the roof allows us to avoid putting up guttering, so it gives a really clean edge, and even in the renders were we all excited enough with it to commit, and think about getting ready to build it!!
So if there is any interest, I can carry on through the rest of the design/ build stages!?
Edited by cRaigAl205 on Wednesday 1st January 18:19
Edited by cRaigAl205 on Thursday 22 May 13:13
Edited by cRaigAl205 on Thursday 22 May 13:14
Edited by cRaigAl205 on Wednesday 4th June 10:52
Edited by cRaigAl205 on Wednesday 4th June 10:53
Edited by cRaigAl205 on Wednesday 4th June 11:06
The planned thickness for the soil is 5inches, so can retain a surprising amount of water (and weight, which was obviously calculated for!)
The planting strategy has been to stick to native british wildflowers, which are surprisingly hardy things, and can cope with most weather conditions (if you think of most meadows, they just dry out and go to seed, but always return when the weather cools down)
It is recommended to use quite a low quality soil (poor in nutrients) so weeds actually struggle to grow, as it is better suited to the wildflowers hardy disposition
We also planned to sneak in a basic irrigation system, just in the event of any major drought the roof can be kept alive, if wanted.
I'll sort out some of the CAD detailed drawings to show, before making a start on the construction stages
The planting strategy has been to stick to native british wildflowers, which are surprisingly hardy things, and can cope with most weather conditions (if you think of most meadows, they just dry out and go to seed, but always return when the weather cools down)
It is recommended to use quite a low quality soil (poor in nutrients) so weeds actually struggle to grow, as it is better suited to the wildflowers hardy disposition
We also planned to sneak in a basic irrigation system, just in the event of any major drought the roof can be kept alive, if wanted.
I'll sort out some of the CAD detailed drawings to show, before making a start on the construction stages
Funk said:
What do they do and why are they clever? Never seen them before.
There is no down pipe as such, there is a bunch of chain, gathered around the drain hole opening in the roof above. The water runs down the chain, and into a drain below.Generally known as drip chains. Pretty cool- can be brushed aside for moving things around the patio, and never block, or perish/fade like plastic guttering.
cRaigAl205 said:
The planting strategy has been to stick to native british wildflowers, which are surprisingly hardy things, and can cope with most weather conditions (if you think of most meadows, they just dry out and go to seed, but always return when the weather cools down)
Good theory but try growing a patch of 'wild flowers' at ground level first, and see how you get on. I would almost bet money that you will not have the wildflower roof of your dreams, but before long a patch of ugly scrub/tatty grass.Wildflower meadows work in nature because they are the natural ecological condition of the land in that area. You can't just sow seeds somewhere else and expect to get the same result, because it's artificial.
Sedum would be a more practical alternative I think.
You are probably already well ahead on this but here are some good substrate suppliers that will mix up a crushed brick/compost combo to suit your preferences to help with keeping weeds down.
If you are going for wild flower, planting can be done very cheaply with seed rather than turf so long as you don't mind a bit of a wait but bear in mind that even with a slow growing mix it should be cut/strimmed once a year once it is established.
If you are going for wild flower, planting can be done very cheaply with seed rather than turf so long as you don't mind a bit of a wait but bear in mind that even with a slow growing mix it should be cut/strimmed once a year once it is established.
Unlike most small extension builds, the project was fully detailed in CAD, as its our first built project, we wanted to be confident about materials, levels and finishes, as well as ensuring we could satisfy building control at every stage. The drawings were also invaluable for discussion/ deciding how we were going to build it, as we only had standard DIY home maintenance experience before we started!
Overall extension section. Beam and block floor (due to the heavy clay/ heave precautions in the area, foundation blocks, standard brick and thermalite cavity wall, and then the green roof.
Roof light detail: Standard Velux centre pivot electricaly operated windows. Fitted in Velux "kerb" boxes, which have two main purposes- they raise the windows out of the soil/ growing layer, to remove any chance of plant/damp ingress around the windows, and increase the angle of the pitch to allow the use of the standard centre pivot roof windows- at 10 degrees the roof is too shallow for them, and we would have had to use the perspex "dome" roof lights, which I'm not really a big fan of, both aesthetically and for day-to-day use, I much prefer the openable standard veluxes.
Roof edge detail: as the roof is quite thick due to the quite unusual loading (the rafters are 2x9inch), we wanted to maintain an exposed eaves, with thinned joists to give a tapered edge to the roof, to allow it to appear thinner.
The roof is waterproofed with a butyl rubber sheet, with factory bonded joins, so forms a completely waterproof layer. This is then protected with a really tough geotextile layer. As mentioned, 5 inches of growing medium (soil!). The edge drainage is dealt with via a gravel channel at the lowest point, through rubber welded tubes down onto the drip chains.
A large 5 inch triangular "arris" rail is fixed to the edge of the roof, to prevent the soil slumping down/off the roof. And it is all trimmed/smartened up with oak weather boards.
Overall extension section. Beam and block floor (due to the heavy clay/ heave precautions in the area, foundation blocks, standard brick and thermalite cavity wall, and then the green roof.
Roof light detail: Standard Velux centre pivot electricaly operated windows. Fitted in Velux "kerb" boxes, which have two main purposes- they raise the windows out of the soil/ growing layer, to remove any chance of plant/damp ingress around the windows, and increase the angle of the pitch to allow the use of the standard centre pivot roof windows- at 10 degrees the roof is too shallow for them, and we would have had to use the perspex "dome" roof lights, which I'm not really a big fan of, both aesthetically and for day-to-day use, I much prefer the openable standard veluxes.
Roof edge detail: as the roof is quite thick due to the quite unusual loading (the rafters are 2x9inch), we wanted to maintain an exposed eaves, with thinned joists to give a tapered edge to the roof, to allow it to appear thinner.
The roof is waterproofed with a butyl rubber sheet, with factory bonded joins, so forms a completely waterproof layer. This is then protected with a really tough geotextile layer. As mentioned, 5 inches of growing medium (soil!). The edge drainage is dealt with via a gravel channel at the lowest point, through rubber welded tubes down onto the drip chains.
A large 5 inch triangular "arris" rail is fixed to the edge of the roof, to prevent the soil slumping down/off the roof. And it is all trimmed/smartened up with oak weather boards.
Mobile Chicane said:
The two Velux windows grate with me. I think a domed circular 'light pipe' would look much nicer.
The two rooflights were requrired (rather than one big velux, for example) as we needed something that fitted between the rafters, with minimal trimming, as the roof weight is not insignificant! We estimated 2.3 tones of soil would be required to reach the desired thickness!!We did initially consider light tubes, but wanted to be able to open the rooflights to allow ventilation. The major reason why they look clunky in the renders is that the model of them wasnt particularly accurate, they look much better in the flesh! Dressed in lead we were confident they wouldn't stand out too much.
Simpo Two said:
Good theory but try growing a patch of 'wild flowers' at ground level first, and see how you get on. I would almost bet money that you will not have the wildflower roof of your dreams, but before long a patch of ugly scrub/tatty grass.
Wildflower meadows work in nature because they are the natural ecological condition of the land in that area. You can't just sow seeds somewhere else and expect to get the same result, because it's artificial.
Sedum would be a more practical alternative I think.
The benefit of the roof as we designed it is that the only major expense is the plants- if they fail, then a seedum matting can be installed later. With the correct growing medium (a mixture of crushed recyled brick, and a clay-based soil, there is no major reason why the wildflowers shouldn't thrive. After all, its a well drained, nutrient-poor area facing due south. Wildflower meadows work in nature because they are the natural ecological condition of the land in that area. You can't just sow seeds somewhere else and expect to get the same result, because it's artificial.
Sedum would be a more practical alternative I think.
So, onto site, and onto the first stage- digging!
Given the narrow passageway to the front, and the tight nature of the extension, between the existing house, and the neighbours garge, we decided to take on the digging ourselves, by hand, with no minidigger etc!
We roped in one of my best mates for the build, so at least there were three of us!!
Thats my partner and I in the foundation trench we dug! Approximately 1.6m deep into the horrible London clay. Its like trying to cut cheese at times. Backbreaking work, but oddly satisfying. When we were in the swing of it, we were filling a 12ft skip in a day.
We also had to resite a manhole (replaced with a plastic inspection chamber).
Foundations were poured (again mixed ourselves in a standard mixer, and barrowed around- no ready mix for us!) and the level brought up using foundation blocks, with a lintel over the pipe to the manhole
Given the narrow passageway to the front, and the tight nature of the extension, between the existing house, and the neighbours garge, we decided to take on the digging ourselves, by hand, with no minidigger etc!
We roped in one of my best mates for the build, so at least there were three of us!!
Thats my partner and I in the foundation trench we dug! Approximately 1.6m deep into the horrible London clay. Its like trying to cut cheese at times. Backbreaking work, but oddly satisfying. When we were in the swing of it, we were filling a 12ft skip in a day.
We also had to resite a manhole (replaced with a plastic inspection chamber).
Foundations were poured (again mixed ourselves in a standard mixer, and barrowed around- no ready mix for us!) and the level brought up using foundation blocks, with a lintel over the pipe to the manhole
Please tell me you're not putting a green roof on rubber?
There are proper plants available for your application, and you're growing medium is over the top for that area.
You can fit a leaky pipe system easily enough. Google Blackdown for plants.
Why such an extreme fall in the construction? Despite your slip arrester it will still slide without a check every 500mm.
We fit approx 100,000 m2 of these a year and if they're not done correctly, they will die. What form of maintainence access have you got, and what do building control say about it?
There are proper plants available for your application, and you're growing medium is over the top for that area.
You can fit a leaky pipe system easily enough. Google Blackdown for plants.
Why such an extreme fall in the construction? Despite your slip arrester it will still slide without a check every 500mm.
We fit approx 100,000 m2 of these a year and if they're not done correctly, they will die. What form of maintainence access have you got, and what do building control say about it?
roofer said:
Please tell me you're not putting a green roof on rubber?
There are proper plants available for your application, and you're growing medium is over the top for that area.
You can fit a leaky pipe system easily enough. Google Blackdown for plants.
Why such an extreme fall in the construction? Despite your slip arrester it will still slide without a check every 500mm.
We fit approx 100,000 m2 of these a year and if they're not done correctly, they will die. What form of maintainence access have you got, and what do building control say about it?
Yep- 1mm butyl rubber with upper and lower polypropylene geotextile . We researched some green roof books rather than "sytems" which seem to over-complicate it for the DIY-er. Will slippage really be an issue? With a 10degree pitch, its not an unnatural angle for plants to secure soil in nature.There are proper plants available for your application, and you're growing medium is over the top for that area.
You can fit a leaky pipe system easily enough. Google Blackdown for plants.
Why such an extreme fall in the construction? Despite your slip arrester it will still slide without a check every 500mm.
We fit approx 100,000 m2 of these a year and if they're not done correctly, they will die. What form of maintainence access have you got, and what do building control say about it?
The growing medium is on the thick side of what is required. But we figured the extra soil would retain moisture in the summer, and reduce the chance of requiring irrigation. Indeed, continuous leaky pipe was indeed the chosen irrigation system.
Building control were initially quite skeptical (just of the green roof in general, as he hadn't seen one before) however he was satisfied with anchor points for work restraint, rather than fall arrest, and he was happy not to have edge barriers, given the infrequent nature of access required for a single storey green roof. I think it being residential helped as well.
Edited by cRaigAl205 on Wednesday 1st January 18:59
Beam and block flooring arrived and installed
Made a start on the brickwork. Not bad for our first attempt. We weren't particularly quick at it, but it looks better than a great deal of the brickwork you see about the place (and generally much better than the rest of the brickwork we were trying to match to!)
Eventually got up to the start of the roofheight, and the steelwork arrived.
Knocking through was quite stressful, but we had a family member who is a builder come down for the day to assist/supervise. Shifting the concrete padstones up was not insignificant work!
Knocking through to the kitchen really made a difference to the feeling of the downstairs
Made a start on the brickwork. Not bad for our first attempt. We weren't particularly quick at it, but it looks better than a great deal of the brickwork you see about the place (and generally much better than the rest of the brickwork we were trying to match to!)
Eventually got up to the start of the roofheight, and the steelwork arrived.
Knocking through was quite stressful, but we had a family member who is a builder come down for the day to assist/supervise. Shifting the concrete padstones up was not insignificant work!
Knocking through to the kitchen really made a difference to the feeling of the downstairs
It will take time for roots to establish, and with a medium that depth, they won't hit the bottom anyway, a few good downpours will double the weight of the medium and it will slip on the filter fleece.
Butyl is an error, factory welded or not. We ripped up a housing estate park area in Finsbury Square last year laid on Butyl, it had lasted a year.
Butyl is an error, factory welded or not. We ripped up a housing estate park area in Finsbury Square last year laid on Butyl, it had lasted a year.
As Im sure you've guessed, I'm writing this retrospectively, and even in the storms we have had this winter (with excessive rain) the only lightly established roof hasn't slumped at all. What issues were there with the butyl? My understanding is that it has a fairly long life expectancy?
And for the future- what would you recommend instead?
And for the future- what would you recommend instead?
cRaigAl205 said:
As Im sure you've guessed, I'm writing this retrospectively, and even in the storms we have had this winter (with excessive rain) the only lightly established roof hasn't slumped at all. What issues were there with the butyl? My understanding is that it has a fairly long life expectancy?
And for the future- what would you recommend instead?
These are the masters of green systems http://www.bauder.co.uk/green-roofsAnd for the future- what would you recommend instead?
Seams on butyl especially at upstand junctions will fail earlier than any other system.
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