Gina's Observatory

[mcrossley]

Going back to your roof, if you use corrugated sheeting (bitumen, plastic, or metal) then you can get away with just a frame to support it, you wouldn't need continuous sheeting under it. That may save some weight.

[Tom How]

WOW!! What on earth are you going to put in there??? That's flooring sufficient to take a three piece suite and a lot more!

The flooring I'm thinking of (18mm chipboard, 600x2400) has tongue and groove on all four sides. It will also go through the loft hatch

Tongued and Grooved Chipboard Flooring - Chipboard Flooring - Sheet Materials -Building Materials - Wickes

Not sure I'd fancy using chipboard in an external application like an observatory... not that I have much experience in such matters!

[Astrokev]

I guess plywood would be better with the possibility of dampness coming up from below. I'm not sure that it needs to be 18mm thick though - maybe 12mm would be sufficient. OK so the difference is only £20 but all these extra bits mount up.

Gina- I used 12mm exterior ply recently when renovating an old shed floor. I was a unsure whether it would be strong enough and might flex, but it's actually very solid. I guess it depends a lot on your final design for floor support. My shed is supported on a flat concrete base which obviously helps.

Oh, and I bought it at a local garden builders merchants, which was much cheaper than Wickes. Wickes have good proces on some things, but not others. It definitely pays to shop around.

Kevin

[Gina]

Sounds like 12mm ply wins the day. I have planned joists at 400mm spacing and I think 89x38x2400 studwork. I have some 8"x4" beams I plan to use for the main frame around the outside. These will probably be supported on 6 concrete piers rather than a continuous concrete foundation. With damp-proof course between concrete and wood.

I have continued excavating the site using the rotovator this afternoon and evening and shifted another cubic yard of soil and stones. I think the main area is nearly deep enough. I've continued down as far as the clay in the middle near the eastern end where the pier is going. It's quite possible to go on down with the rotovator, pushing the soil out of the trench with the blade guard at the back. I'm over a foot down now and removing clay.

I've also discovered this evening that a farmer we know has a digger - I'm going to ask him how big it is and if it might be available to me. Mind you, I'm not doing badly with the rotovator

[JamesF]

Diggers are proper toys though

It might well be just what you're after. Plenty of farmers have something like an 18" bucket to fit the rear of a tractor because they're very useful for digging field drains. He might well be able to do in a couple of minutes what would take you a couple of days otherwise.

I do know what you mean about the rotovator though. We have an old Howard 350 which would probably get to Australia if you could hold it down long enough.

James

[Astrokev]

At this rate you may have to plan for a taller pier --- just to see out of the hole. ;-)

[Gina]

Very good Kev

Cold and windy here today with no sunshine to warm it up, so I don't think I shall be doing much outdoors unless it warms up this afternoon. I checked levels with my laser level yesterday evening and I'm about right

So I'm concentrating more on the planning today. I think I have pretty much sorted out the floor and walls but still not happy about the roof. Two things - the choice of materials and the direction of slope.

Roof materials. Been looking at the various roofing felts and methods of fixing. I'm not sure the cheap felt would last very long and being lightweight and rather fragile, would be difficult to handle without tearing. The better quality felt starts getting expensive, the best needing two layers - and under and a top sheet. No doubt this would pay in the end in lasting properties. But the alternative of corrugated bitumen starts looking more promising. The cost difference is less and there is no doubt that the bitumen sheets would be a lot easier to fix onto the framework. I have had experience of fixing corrugated sheeting of various sorts but not of roofing felt. I already have two (or maybe three) of the larger corrugation type bitumen. That would save nearly £30. I reckon I would need 7 sheets with the sheet size of 950mmx2m and an overlap sideways of 1 corrugation of 95mm.

Roof Slope. It's a question of where the runoff rainwater goes. If I sloped the roof to the side as is popular, the rainwater from the warm room roof will run onto the running track unless I can incorporate guttering. With the present design, this is difficult. So I'm looking at going back to sloping the roof downwards towards the warm room. Since the obsy roof will be wider than the warm room by a corrugation, rain falling on the side edges will fall onto the running track. But I could put guttering on the ro roof edge above the warm room roof. And also on the warm room roof above the doorway.

[Gina]

Been looking more at roof design. There is a serious disadvantage of sloping the roof lengthways - it will make the obsy end very high if I allow headroom at the warm room doorway at the other end. According to the Wickes advice sheet for corrugated roofing, bitumen roofing wants a minimum of 1 in 6 slope to avoid a lot of overlap between pieces. That would make the obsy roof getting on for 9ft at it's highest. That is too much really.

So it looks like I'm back to the sideways sloping roofs which I've been taking another look at. I think I could put guttering virtually in the top of the warm room wall. See attached drawing.

[nightvision]

I don't think it would be easy to get a good seal around the gutter (driving rain in windy conditions could find its way in to your wall), better to increase the overhang and mount the gutter on the outside of the warm room wall.

[Bizibilder]

I agree with nightvision - the roof should overhang the wall (and possibly have a lip pointing downwards) the gutter should be on the outside of the wall.

Just realised - you MUST have a slope on the gutter (maybe 1/2" in around 4 feet which is 1:100) to ensure the quick run off of the water. - You will be amazed just how much water comes off the roof! My 6' x 6' shed can fill a large water butt in one short sharp shower (which is what it did the other day - I was amazed as the butt was empty when I last looked). If the slope is too shallow you may get water staying in the gutter - not a good idea in the winter where it may freeze and "dam" the gutter.

[Gina]

Yes, I was planning to have a slope on the guttering. I also agree about the difficulty of sealing around the guttering. Looks like I shall have to make the warm room a bit smaller and provide extra support for the part of the running track that goes past the warm room. The roofing will most likely be corrugated bitumen. It will need shaped pieces to fit below and follow the profile to stop wind blown rain getting in. There doesn't seem to be any filler foam designed for the larger profile - only 3" for the PVC roofing. I considered that but I think the bitumen would be better. Cost is similar.

Here are the two ideas.

1. With the guttering atop the warm room wall and

2. Outside with a bigger gap between rolling section and warm room wall.

[nightvision]

Hmmm looks more complex than I thought it would be obs roof might jam on the warm room gutters if it flexes side to side.

The obs will never be open when it rains so I wonder if its possible to simplify things by re-thinking the gutter system? Not sure... just thinking it over.

[nightvision]

...

[Gina]

Hmmm looks more complex than I thought it would be obs roof might jam on the warm room gutters if it flexes side to side.

That's only a rough drawing and I shall make sure there's plenty of clearance. The join of the moving and fixed parts is quite complicated and not easy to seal.

The obs will never be open when it rains so I wonder if its possible to simplify things by re-thinking the gutter system? Not sure... just thinking it over.

True, I wondered that myself but I haven't worked out any simplification so far. If you think of something, let me know, I'd be grateful

[Astrokev]

Gina

Did you see this thread for a ROR obs over warm room design from last year? If not, may give you some ideas, or help you visualise your own design.

http://stargazerslounge.com/diy-observatories/111011-observatory-build-progress.html

Kevin

[astroimpulse]

Blinky's ROR (pics in last page) is one of the few that I think looks really smart and has made me dither on the final decision. I love it and it retains very good aesthetics too

[Gina]

Yes, there's plenty of good designs to look at I've lost count of how many I've looked at. I agree Blinky's looks very nice.

Here's some detail of how I propose to cover the join between fixed and moving roofs. The moving obsy roof is shown in blue. I'll sort out the details of the sides tomorrow. The roofing material is corrugated bitumen sheets and is very flexible.

[Astrokev]

The gap between the warm room section and the rolling section will need to be quite large to accomodate the WR gutter. How d'you plan to attach the rails for the obs to roll on, to ensure it is structurally robust? I'm not being critical of your design here (I can't think of a better way of doing it) but just interested.

Thanks

[Gina]

The gap between the warm room section and the rolling section will need to be quite large to accomodate the WR gutter. How d'you plan to attach the rails for the obs to roll on, to ensure it is structurally robust? I'm not being critical of your design here (I can't think of a better way of doing it) but just interested.

Thanks

Yes, makes things more complicated. It will need posts down to the ground and struts across to the warm room wall. I'm still mulling over other possibilites re. the guttering but nothing better comes to mind so far.

[Macavity]

Just realised - you MUST have a slope on the gutter (maybe 1/2" in around 4 feet which is 1:100) to ensure the quick run off of the water. - You will be amazed just how much water comes off the roof!

Too true. My test, with a couple of cm fall over 3m, left quite a lot of static water. I sense the fall needs to be greater than that! A back-of-envelope calculation confirms what you say(!) - A short sharp shower has the potential to produce a LOT of water. Dunno what the effect of concentrating this in a small space might be. Maybe a sink-hole or Water butt(s)? Either way it adds a "maintenance" issue. Water conservation is COOL, but if you don't have many plants to water regularly.

My neighbour PROUDLY showed me his (huge, never emptied) Water Barrel. Lifting the lid revealed (to his surprise!) it brim-full, with a threatening... mass of trembling water. Had visions of a "Dam Busters" remake, if the wind got up a bit.

[malc-c]

To a degree I'm going to be facing the same issue with my obsy but I'll sort that out when I come to build it. I think a lot of the issues will get solved on the fly as you progress through the building stage. I'm still working out where to put the door, the original plan had to change due to the gap between the end wall and fence being too narrow.

Whilst it's a good idea to plan in advance, sometimes you can get too wrapped up in the details

[Bizibilder]

I have had to put an overflow pipe on my waterbutt as it fills faster than I can empty it! Nothing clever - just a pipe fitting from the plumbers and about 5m of garden hose to run the excess to a nearby manhole cover in the garden (Just allows excess to find its way into the manhole - there is no direct link) most of the water runs over a flowerbed.

The reason I put the gutter in in the first place was that it became obvious that water running off the roof would have quickly undermined the concrete slab that my observatory is built on - it is just a slab laid directly onto the soil, about 2" is "below" the surface where I stripped the turf off and 4" is "above" ground level.

[Macavity]

Nothing clever - just a pipe fitting from the plumbers and about 5m of garden hose to run the excess to a nearby manhole cover in the garden...

Ah, interesting (practical!) idea. Don't want to start digging drains...

[Gina]

I have no doubt the rainwater running off the roofs needs proper handling. If it's just allowed to pour straight off the roof it soon digs itself a deep hole in soil and/or finds it's way under the footings. There is a drainage ditch just the other side of our boundary and the rainwater can run into that - the correct place for surface water. Some of our sheds already discharge rainwater into this ditch.

Been moving soil from the site down to our other plot to build up the vegetable area. The topsoil I'm removing is of very good quality having been fertilised by goats so want to make good use of it. Had to stop now as it's started raining.

Back to obsy design... Here is a rough plan of the obsy and warm room - floor and roof plan. Some detail not shown for clarity.

[Gina]

duplicate post