building a Walapini greenhouse . opinions welcome .

you used the same or simular material for your roof ? what size was it and over time did you notice the roof sag more ? cozz im thinking i could do it with out roof beams . but over time it would stretch and sag.
as for the gutter. the roof has no defining edge like it would up against a lenght of wood. its being held in place by the wieght of the bags on top of it. so it has to pass between two bags. there are only two designs . i ether stop the water before/at the bags . or i make it so the water flows through gaps in the bags and then collect it the other side. maybe a few small pipes to let the water flow past the bags. then i have the edge of the tarp to put up against the gutter. thig is i have to make the right choise cozz once ive put the bottem tarp on and then the top tarp, it will be sealed forever on till its changed for a better roof. so once i get the roof on . modifacation will be hard to do . ill be finishing the 3 layer bags and on to the fourth soon. i wont need to deside till i get a few more layers of bags up . its one of the benefits of such slow progress is that i have plenty of time to plan these things , before i  need to impliment said idea.
happy to get those roof sheets . they are old , but solid for the most part and will do the job of covering the top of the bags from light and added bonus . i dont have to seal the bags water tight between them.
ive got ideas outlined all over this build that i could be talking about , but they are all ideas that dont need to come up time later . but believe me , i spend a lot of time sitting in my garden just thinking about this all. all this digging is just the hard work needed to get to the fun stuff , the building thats going on inside the greenhouse.how can i talk about heater and water contailers when i havent even got a roof on.that and i have glenn and the rocket heater forum part ear makerd for the inside planning.

dillion . ill try and take some more pics today for you.

The specific error message is: "cozz" is a silly English abbreviation; use "because" instead. im sure someone finds the way you talk somewhat silly , ill sound silly to somebody out there. why does it not pull me up on tarp . its a silly abbreviation only used to shorten a word we know anyway. so i cant use the word cozz , maybe cozz its not a real word. well none of these words were real words till they were first used. just saying we type like we talk and its how i talk with a cozz .

Still here! Seems to me letting water flow between bags would be easier... cuz how would you stop it before it reached the bags?

happy you are still here matey . i would hate to think im danceing round the garden takeing pictures of a hole for a guy i dont know and have never met on the internet. kinda sounds dirty when i say it like that ha ha ha .
so i was thinking tarp . then the corner where it meetsbag . plastic gutter layed on the tarp and sealed to the tarp with mastic or silicon . it works so long as the tarp stays still. constent motion i figure would damage the seal. this is why i move the idea down a peg in my mind and moved letting it through and collecting it on the other side. see i have a lot of pure clay , the grey stuff so its good and i have 4 bags of cement. i figure if i lay some pipes between the bags . the bags will seal up around the pipes and if not . no matter to put a bit of sealent around the pipes. then have the pipes drop into or have the tarp poke out the other side. then i have an edge they i can put a gutter up against.
remember even though i exsprct it to be dry between the tarp . at some point the top tarp will start letting in water and when that happens the the bottem tarp takes over and has to convay water away as well. so i like the pipe idea COZZ it lets me drop both tarp water into the same gutter.
as for material . if it was before the bags . it would have to be plastic. but letting water past means i could possable make the gutter out of clay and a touch of cement. i would welcome a 3rd idea if there is one that isnt going to cost me the earth or have me off on a tresure hunt.lol
also i just thought . with the gutter outside the bags means i can get a constent drop with the gutter. i was worring how to get the water to run if that side wall is level.
my knightmare right now . it that it comes time to put the tarps on and they get damaged doing it . i realy can barely aford to replace them after the tools ive had to buy. if you ever get back to civilisation again dillion and you can get a connection that lets you watch youtube . its all there to watch and catch up on. not that im plugging my chanel . but in this case i feel it worth mentioning in your case. i do a daily progress kinda thing. you could catch up on it all. if you know how i would send you a file of it . these pictures dont realy do it justice like a moving picture does.

you used the same or similar material for your roof ? what size was it and over time did you notice the roof sag more ? 'cozz i'm thinking i could do it with out roof beams . but over time it would stretch and sag.  

[note I put an apostrophe between the i and the m after 'cozz and the spell check was happy. but it doesn't work for cozz]
Mine are 8 feet long and 2 feet wide. They are installed with one hump overlap on he sides and 1 inch overlap on the ends. My greenhouse is just under 16 feet square. Because skinny trees are available here like at the permies lab I used them across every 2 feet. Every 4 feet would hold them for rain but not for snow. They are fastened with screws that have a rubber washer through the top of the hump where they overlap into each beam and one in the middle to keep the wind from rattling them  If I take the roof off again I will put a sheet of clear plastic underneath so that there is an air space at the humps.
The water can be collected by splitting a plastic pipe lengthwise and snapping it over the edge. If you are still planing on having a bag on top the collection pipe then could be between the bags.

i was like wtf , this guy has a green house 8 feet long , but two feet wide. i stopped there trying to think how a two foot wide greenhouse works lol. thanks for the tip . im told ive been touched by the dislexic fairy.
so thats 16feet by 16feet or you mean there is 16 square feet volume. i make it just shy of 5 meter square. 25sq/m of floor space. but im guessing you get a fair layer of snow on top, to need so i guess you need the beems just over a meter apart. you wouldnt notice and sagging from the tarps weight on its self stretching it. this is what i was getting at. i was worried that a 5 meter stretch would be too much to exspect it to hold its self up. i was in two minds about nailing the tarps down . but i think now that i will . maybe put some mastic or silicone over the wholes. i was worried about humps in the tarp that the water couldnt rollover. ether way im going to have to deal with water at the low end of the tarp. no way to rig it otherwise.
"The water can be collected by splitting a plastic pipe lengthwise and snapping it over the edge" . the edge of what presicly. so i got a bag/tarp sandwich and the water will collect where bag meets tarp. my idea was to lay a channel between the bags, but above the tarp. these channels between the bags will run to the outside edge of the bag.then i build a gutter below that to collect it that runs the length of the wall to the drain. if i make it with the gutter below both tarps i can do the same with the bottem tarp for when the top one starts letting in water.for sure i would like to put a propper roof on . but later once ive saved up for it.
right now i have 8 lengths of wood, long enough that if i butt two length wise they should work, i have one 5 meter length of scafolding pole, and a couple of bent branchs , oh and one bent tree. anything else need to be found or payed for. ive payed *tools not included* around £47 on the tarps and £17 on the bags so far , everything else has been scavenged or ive hand it laying around. i have stuff saved in the shed, but its mostly for the inside. i have a hose pipe i plan to use to let the water past the bags and one bit of gutter i plan to use someplace.
but right now is all about building the walls and planning the roof. the moment i put a roof on i need to have someplace for the water to go. so a drain , then a place to hold the water till i need it for the plants. then i can pause. right now i cant stop time is against me. first of all i want it by winter in a somewhat working manner. plus i realy would like to get the heating system in before the colder weather hits. i know im down deep . but i have no idea how warm the ground will make it.

"The water can be collected by splitting a plastic pipe lengthwise and snapping it over the edge" . the edge of what presicly. so i got a bag/tarp sandwich and the water will collect where bag meets tarp. my idea was to lay a channel between the bags, but above the tarp. these channels between the bags will run to the outside edge of the bag.then i build a gutter below that to collect it that runs the length of the wall to the drain. if i make it with the gutter below both tarps i can do the same with the bottem tarp for when the top one starts letting in water.for sure i would like to put a propper roof on . but later once ive saved up for it.  

Over the rippled edge of the roofing materiel so that the rain flows down the little valleys and then drips into the pipe.
My roof has one row of eight roof panels on the south side and then another row of eight above it overlapping at the center beam. The south east corner is the lowest so all the water runs off the south edge and then along the gutter to my collection tank on the SE corner.
Yes I have about 25 square meters of floor space covered by 16 sheets of roofing. How many sheets of roofing do you have?

i cant aford clear corigated plastic sheet or the stuff that comes with it. i just plan for the two tarps for now.later ill put a plastic top on , when i can aford it . for now im just trying to make it cheap.
i came to a realization last night . none of this will work in the long run. my point is now matter how i collet it past the bags. the tarp wi;; always leak.leak as in water runs down the underside of the tarp. so its all good till the second tarp starts to leak.then ill have water running down the underside of the bottem tarp. i have to plan for the long run i have no idea when i will have the money to re roof it. so i fidure i may as well plan to stop the water before the bag. maybe poke a few holes in the tarp in the right places to let water drop through . maybe an inside gutter/drain. not sure with these bags if i could get a desent drop along the lowest edge to get the water flowing to a corner.
thinking now. i could let the water past the bags if that is the best plan. but i will have to make something to collect the future water that will run down the underside.
i think i may revisit an older plan i had. i have to cover the bags between the tarps from the sun. i had planned to do this with exspandable foam. spray it around the edge and it should cover it. but the foam will also seal from water , im think. then have a gutter for the top and the bottem tarps underneath each. if i make it so the water drops through the tarp.once the tarp starts leaking, it wont be a bother . the gutter will collect above and below.

sorry i havent posted . the whole greenhouse build is paused . i have got the houseing association involved . ive been waiting nearly a month for them to come and talk to me about greenhouses. i realy cant build untill we have this sorted out. i have to say im a little irritated at how slow there responce. but once its all sorted . ill be back to buiding.