the yesyes observatory - let the planning begin

[fwm891]

Go with James on that

[fwm891]

Go with James on that

[yesyes]

forum acting up again? ;-)

[fwm891]

One way of making a point!

[yesyes]

Does anyone know what this piece of "decking hardware" is called that this guy puts in the concrete at 2:14 in this video? This looks like just the right thing to hold the frame joists to the foundations.

https://www.youtube.com/watch?feature=player_detailpage&v=tMga7duPaKM#t=134s

[nightvision]

Closest I've seen this side of the pond: http://www.screwfix.com/p/concrete-in-post-supports-100-x-100mm-pack-of-2/70197

[nightvision]

Or cheaper: http://www.screwfix.com/p/sabrefix-stand-off-post-anchor-base/85498

[yesyes]

great, thanks! I found the same on ebay for slightly cheaper but with postage cost. Still a few £ cheaper than Screwfix for the 14 I would need.

But then it occurred to me that I could just make something similar myself from old metal pieces. It doesn't have to look as nice. The UPVC cladding will be about 20cm lower than the top end of the joists, so the strapping won't be visible in the end. Also, I would only need the metal sticking out from the concrete at the inside of the floor frame. I was planning to have the outer edges of the joists and the edges of the foundations aligned so that the cladding can easily go lower than the top of the foundations (if that makes any sense...). So strapping on both sides of the joists might get in the way....

[yesyes]

I'm not sure I explained this properly....

So here is a quick drawing (not to scale!!)

This is viewed from the side of one of the foundations. There probably won't be enough space between cladding and floor frame for another strapping thing and it would also be too close to the edge of the foundation....

[fwm891]

Chris, Placing straps in molten concrete seems very awkward for a job of your size. Why not just drill through your floor frame into the concrete and use a hammer-in fixing (basically a long rawl plug and screw that goes through the floor frame and into the concrete in one go.

i.e.: http://www.screwfix.com/p/rawlplug-ffi-hex-head-frame-fixings-10-x-100-pack-of-25/73814

[yesyes]

That would make things a lot easier... And that is strong enough?

What length would I need? The one you linked to seems to be 100mm long, which is just the thickness of the joist. 200mm perhaps?

[yesyes]

I have now designed the window into the Sketchup project. Does this look alright?

yesyes observatory_5.skp.pdf

[Astrokev]

Hi Chris

The hammer through rawl style fixings look a simpler and more effective solution to me, but I've not checked whether you can get them in the length you'll need.

One thing I'm really interested in is whether you'll be putting damp proof membrane between the foundations and the floor joists, and how you'll fit this?

Kev

[nightvision]

That looks very slick, what spacing are you using on your floor joists and noggins? Not sure what type of flooring you intend to install (I'm sure you've got this covered but doh! moments can happen in this area, how do I know??) but it's a good idea to map out the joist positions to make installing 2420x1220 sheets (OSB etc) easy when it comes to seam alignment/support. I am currently considering fabricating a very springy floor to provide some shock-absorbing characteristics.

[yesyes]

Hi Chris

The hammer through rawl style fixings look a simpler and more effective solution to me, but I've not checked whether you can get them in the length you'll need.

One thing I'm really interested in is whether you'll be putting damp proof membrane between the foundations and the floor joists, and how you'll fit this?

Kev

I've got a 30m roll of 112.5mm wide DPC. That will go under the frame joists where they touch the foundations. I was planning to bend the sides of the DPC up and then nail to the joists there. But the DPC might not be wide enough for that. I've also got a tin of bitumen paint that I could use there instead of or in addition to the DPC. The bitumen paint might be better as the DPC would need a hole cut in it to fix the joist to the foundation.

[yesyes]

That looks very slick, what spacing are you using on your floor joists and noggins? Not sure what type of flooring you intend to install (I'm sure you've got this covered but doh! moments can happen in this area, how do I know??) but it's a good idea to map out the joist positions to make installing 2420x1220 sheets (OSB etc) easy when it comes to seam alignment/support. I am currently considering fabricating a very springy floor to provide some shock-absorbing characteristics.

Thanks ;-)

Someone told me on here (can't remember who now) that 16" centres would be ideal. I'm mostly a metric guy so I have drawn it with 400mm centres. But I'm still flexible with that...

When we bought the house there were some sheets left from when they boarded the loft. I was planning to use these and buy a few more if they are not enough...

That reminds me, I wanted to measure them...

They look a bit like OSB but smaller wood chips.

[opticalpath]

Sheeting materials still come in imperial sizes, like 8' x 4' (2440 x 1220mm), and that's the reason for 16" centres for the joists. At that spacing, it means that when you lay flooring sheets you can arrange the edges to meet exactly along the centre lines of joists, so all the edges of sheets are well supported without the need to trim the sheets. 400mm spacing is close, but the small difference from 16" will mount up and after four or five joists, standard full-size sheet joins will no longer line up with the centres of the joists. If you want to stay metric, just set your joists out at 406.67 mm centres.

Adrian

[nightvision]

What Adrian said... and of course I meant 2440x1220 not 2420x1220 but watch out for the smaller true metric (600-1200-2400 etc) dedicated T&G flooring boards, like the stuff you might find in the attic.

[yesyes]

Thanks!!

I didn't get around to measuring the floor boards I have yesterday. I'll do that and then re-arrange those joists in the drawing. Anyway, I noticed that I could probably save one in the warm room if I adjust the spacing a bit.

On the other hand, I will need almost exactly two 2440x1220 sheets per room. So any slight offset would not have a chance of adding up much. But still, better to do it properly while I have the chance... ;-)

[nightvision]

Just remembered another tip; use the minimum number of screws to hold your sheet flooring in place (not nails), that way you will always have easy access to the underside of your construction. Only put a few screws at the periphery and none anywhere else, it wont move but you will be grateful if you forget to route something, want to install foam insulation or you end up with critters making a home underneath!

[yesyes]

Today I have finally started with the build!! New build thread here:

http://stargazerslounge.com/topic/186841-the-yesyes-observatory-the-build/

[yesyes]

I have also measured the floor boards I have on the loft. They are 2400 x 620mm. They were quite hard to get to, under some other boards, so this measurement might not be very exact.

I'm not sure they are good enough for outdoors though. I have taken a picture of a small piece of the board. Is that something I can use for the obsy floor?

[JamesF]

I'm not sure I'd use that for an outdoor floor. I'm aware of two different sorts of flooring chipboard like that. One is water resistant and the other isn't. The water resistant one has a slight green tint to it. Outdoors I think moisture in the air would eventually get to the non water resistant type and if you have a leak it could turn into a nightmare to sort out.

James

[yesyes]

Thanks James. It looks completely grey, no green tint. I won't use it for the floor then. Better get some OSB sheets. I will only need 4 2440x1220 sheets, so that's not a big cost.

Would I be able to use them for the inside of the walls though? Or better not use them outside at all?

[Gina]

I used 11mm OSB on my warm room roof - covered with rubber roofing. I used 6mm plywood on the scope room RO roof for lightness and strength. I also used 6mm plywood on the warm room inside walls and ceiling, mainly for appearance. As I understand it, the right grade of OSB is alright for sheds as long as it's not used on the outside with just a coat or two of paint. I seems to be more weatherproof than chipboard. As you may remember, I used 20mm T&G for my floor.