Gina's Observatory - The Build

[Gina]

If I may make a suggestion: In the odd few places where you may need access in the future it may be better use screws rather than nails. The boards round the base of the pier for example.

Sounds a good idea

With nails I believe it's usual to use two per board per joist. If I used screws that would be quite a lot! I wonder if one would be adequate.

[mcooke999]

I'm planning to add some noggins in strategic places later, before I fix the floorboards.

I want to see what offcuts I get. I already have some which just need cutting down to length.

This is what I was planning but maybe this is overkill. Certainly the left hand end ones are unnecessary

because the joists are screwed to the beams so held at the bottom and also to the framework of the obsy east wall at the top.

I am a structural engineer by profession.

It is usual to skew nail noggins at third points between all timber floor and roof joists. This is to prevent what is known as 'lateral torsional buckling' of the joists.

Also, what type of roof construction are you planning to adopt? If it is timber rafters etc... then make sure you use galvanised straps to strap the roof down to the rest of the structure. This is to prevent wind suction from pulling the roof off!

Also, not that it matters now because it is cast in but the steel reinforcing bars in your pier should not have really been placed in the ground as this will (over a period of years possibly exceeding the design life of this building) rust due to moisture in the ground. For future reference, any steel reinforcement in concrete should have a minimum of 40mm cover (distance between any given surface of concrete and the steel) to prevent external water from effecting the steel.

[Gina]

I am a structural engineer by profession.

It is usual to skew nail noggins at third points between all timber floor and roof joists. This is to prevent what is known as 'lateral torsional buckling' of the joists.

Also, what type of roof construction are you planning to adopt? If it is timber rafters etc... then make sure you use galvanised straps to strap the roof down to the rest of the structure. This is to prevent wind suction from pulling the roof off!

Also, not that it matters now because it is cast in but the steel reinforcing bars in your pier should not have really been placed in the ground as this will (over a period of years possibly exceeding the design life of this building) rust due to moisture in the ground. For future reference, any steel reinforcement in concrete should have a minimum of 40mm cover (distance between any given surface of concrete and the steel) to prevent external water from effecting the steel.

Thank you for your advice I'll bear it in mind.

[Gina]

Fine weather today and I've "unwrapped" my building. There were dozens of gallons of rain water collected in the tarp between supports and some rain has got inside but obviously the tarp saved a lot. We had a lot of heavy rain overnight - 4.5mm according to my weather station. The tarp and rainwater were very cold and my fingers have just unfrozen!! But I wanted to get the cover off as early as I could to let the woodwork dry out. I have plenty planned to do today!

[Gina]

Making reasonable progress today with plenty of breaks to warm up - there's a cold breeze.

[mcooke999]

To protect your timber against the weather, you could consider treating them off site prior to installation on site. You can buy special timber treatment from any DIY shop and paint apply it to the timber inside somewhere. This will protect it from the rain.

[JamesF]

Making reasonable progress today with plenty of breaks to warm up - there's a cold breeze.

The forecast suggests the weather might be reasonable for the next few days, so with any luck we'll be seeing a fair bit of progress. I'm looking forward to seeing some solid structure. It'll really feel like it's coming together then.

James

[Gina]

To protect your timber against the weather, you could consider treating them off site prior to installation on site. You can buy special timber treatment from any DIY shop and paint apply it to the timber inside somewhere. This will protect it from the rain.

The timber I bought in was all pressure treated - the secondhand beams I used under the joists, I treated with creosote.

[Gina]

Fine, though cold, weather today enabled me to further my obsy build

1. Cut extra clearance for the pier in the floorboards.

2. Screwed down joists for the north wall.

3. Took obsy north wall frame down and replaced bottom rail with full length one - covering both obsy and warm room ( as per design change).

4. Cut uprights for warm room north wall and screwed them onto the bottom rail.

5. Erected north wall frame and screwed uprights to top rail.

[Anweniel]

Looks great, been keeping an eye on webcam when pos.

I hoped you planned to leave enough room to swing larger scopes in there, once you get that bug for aperture

[Gina]

Looks great, been keeping an eye on webcam when pos.

Good There seems to be quite a lot of interest in the webcam I have friends in Australia who are watching it when they can too. That's why I have set up the software (Yawcam) to keep the 7pm image overnight.

I hoped you planned to leave enough room to swing larger scopes in there, once you get that bug for aperture

The obsy roof is 8ft square though the inside is a bit smaller due to the thickness of the walls, so I think it will be reasonably future proof. To make it any bigger would have increased the difficulty of build disproportionately.

[Gina]

Thought it was going to stay fine... NOT!!

So I've had to put the tarp back on for overnight. It's properly on now and roped down but here I am starting to haul it over the top at 7pm this evening

[laser_jock99]

To protect your timber against the weather, you could consider treating them off site prior to installation on site. You can buy special timber treatment from any DIY shop and paint apply it to the timber inside somewhere. This will protect it from the rain.

I reckon all my timbers were treated at least 3 times during the build. I started with roughsawn treated timber, gave these a good coat of creosote before any working while they still stacked. Then a further coat once assembled. All cut ends were treated as well. With the real critcal timbers (i.e. the six main uprights) these were left ends standing in a bucket of creosote overnight (both ends) for maximum take up. Probably overkill - but I know that many of these timbers won't be seen again (and therefore can't be re-treated) until the observatory falls down or is otherwise de-commisioned! Given the exposed location I'm expecting my obsy to take a battering from the weather.

[Gina]

I reckon all my timbers were treated at least 3 times during the build. I started with roughsawn treated timber, gave these a good coat of creosote before any working while they still stacked. Then a further coat once assembled. All cut ends were treated as well. With the real critcal timbers (i.e. the six main uprights) these were left ends standing in a bucket of creosote overnight (both ends) for maximum take up. Probably overkill - but I know that many of these timbers won't be seen again (and therefore can't be re-treated) until the observatory falls down or is otherwise de-commisioned! Given the exposed location I'm expecting my obsy to take a battering from the weather.

Yes, I think maybe I should have treated the timber after cutting, but creosote is so messy and slow drying - the build would take ten times as long, and I want it finished before winter. Cuprinol or it's copies would be alright I guess. If we get some good weather, I might bung on some Cuprinol or whatever. Nothing is permanently fixed yet (other than the pier).

[laser_jock99]

Yes, I think maybe I should have treated the timber after cutting, but creosote is so messy and slow drying - the build would take ten times as long, and I want it finished before winter. Cuprinol or it's copies would be alright I guess. If we get some good weather, I might bung on some Cuprinol or whatever. Nothing is permanently fixed yet (other than the pier).

At all costs avoid using any of the acrylic based wood 'preservatives'. These are non-penetrating and will peel off the surface of your wood after a season. They are usually sold in big buckets of varying gaudy colours. 'Proper' treatments are high in volatiles and sold in metal tins!

I agree about creosote being messy- always wear disposable gloves with any of these treatments, there's nasty chemicals in there.

[Gina]

At all costs avoid using any of the acrylic based wood 'preservatives'. These are non-penetrating and will peel off the surface of your wood after a season. They are usually sold in big buckets of varying gaudy colours. 'Proper' treatments are high in volatiles and sold in metal tins!

I agree about creosote being messy- always wear disposable gloves with any of these treatments, there's nasty chemicals in there.

I presume from what you say that Cuprinol and Homebase Woodcare products are not really suitable. I think both come in 5L plastic buckets. I have some of the Homebase stuff and it says low in VOCs (volatiles). Going to Mole Avon tomorrow ( a town and country type shop) so I'll see what they have. A bit more of a professional type shop than Homebase or B&Q etc.

[laser_jock99]

I presume from what you say that Cuprinol and Homebase Woodcare products are not really suitable. I think both come in 5L plastic buckets. I have some of the Homebase stuff and it says low in VOCs (volatiles). Going to Mole Avon tomorrow ( a town and country type shop) so I'll see what they have. A bit more of a professional type shop than Homebase or B&Q etc.

The stuff sold in buckets (low VOC's) is the water based, paint type you need to avoid. Once it's on you'll have a job to put proper wood preservative on later as the acrylic layer blocks penetration into the wood. I used a 25L can of creosote substitute (£30 from the farm supply store) for the frame treatment and the waney edge board outer cladding got a coat of decent Ronseal stuff

Ronseal Total Wood Preserver | Wood Preserver Products | Ronseal

This is >£20 for 5L but looks nicer than creosote!

[malc-c]

This is >£20 for 5L but looks nicer than creosote!

Any pictures. I've used three coats of Crecote (creosote substitute) and love the colour and look but I'm concerned that it doesn't repel water in such a way as other preserves.

[Gina]

Thank you for your replies on wood preserver I'll go for the Ronseal, I think it's worth it. For the outside I'm going for green, to blend in with the surroundings. If I can't get it locally, Amazon do it :- https://www.amazon.co.uk/Ronseal-Total-Wood-Preserver-Green/dp/B0024LE7DE/ref=sr_1_6?ie=UTF8&qid=1316673318&sr=8-6

[Gina]

Managed to get some clear Ronseal Total Wood Preserver. They didn't have green so I just got a 2.5L tin and I'll order some green from Amazon. That was at a different shop.

I did get some roofing felt from Mole Avon though. Went for a heavy weight felt - 30Kg, whatever that means. It was just over £37 for a 10m roll - Wickes "Super Shed Felt" is £36 odd for 8m rolls.

[laser_jock99]

Any pictures. I've used three coats of Crecote (creosote substitute) and love the colour and look but I'm concerned that it doesn't repel water in such a way as other preserves.

Ronseal red colour

[Gina]

Very nice

Missed out on the morning for continuing the build but at least I bought some things towards it

Today's activities towards the build :-

1. Further adjustments to the pier hole in the floorboards.

2. Dividing wall frame (currently held in place with clamps).

3. Some wood cut for the warm room south wall.

No DSLR photos ATM - I'll take some tomorrow - but here's a section of the webcam image.

[Gina]

Fine today with some sunny spells but rather chilly.

Currently working on the floor - adding noggins and treating with Ronseal Total Wood Preserver.

In for a cuppa and to warm up.

[Gina]

Good weather today - fine with sunny spells but a chilly breeze.

Today's progress :-

1. Noggins for joists.

2. Some wood preserver applied.

3. Cut hole for cable duct in warm room floor.

4. Added boarding to fill the gap between obsy and warm room south walls. Used offcuts of floorboard. Cut notch for roll off rail and also to clear joist.

5. Screwed boarding to wall parts, including new piece for warm room wall.

[Freff]

Hi Gina, things are looking good. Glad you could get something done today.

I ordered my Shiplap today, quite a shock at the price. It was £370 for 60 x 5.1m lengths. (306 mts)

If the weather stays fine the obsy should be water tight by next weekend.