Building an Observatory - page 2

The next step I took was to sheet the roof. Once again I used heavy duty sarking to prevent heat and condensation from entering the roof cavity. I then screwed down zinc coated corrugated tin. Placing plenty of screws on each purlin. The observatory is built in a day time windy area. Night time is fine, it is nearly always the reverse of the day. Anabatic winds blow in from the Southern Ocean which is only 5 km's from the site. With that sort of environment it pays to be cautious. The image below shows the sheets going on. I found it good to stand on a trestle and screw the sheets down. I don't think that the structure would support my weight, so this was the best method of fixing.

Once I had the roof sheets on, I set about fixing the barges and fascia's. To fix the fascia I used small blocks of timber that I screwed directly to the roof trusses. I then screwed the fascia onto the timber blocks. A couple of screws per block which penetrate about 20mm should be enough to hold it into position. For the barges, these were screwed directly to the truss. Ensure that your barges are at the same height as the top of the corrugation of the sheet. This will allow the barge caps to fit neatly and prevent water finding its way into the roof structure.

Once you get the barges fitted, you then need to think about the posts for the outriggers. These have to positioned nearly perfectly to the line of the fixed running rail inside the observatory. Deep anchorage is vital to prevent movement of the posts. 300mm of concrete will give you enough anchorage. Lots of bracing, the use of a plumb bob and string lines will help you to get the alignment and positioning of the posts correct. While you are doing outrigger posts you also need to fit the cross bracing that it needed to keep the whole structure stable. Ensure that you house out the posts about 20% of the bracing material and use good quality bolts. The image below illustrates what I am talking about.

Once the sliding roof is working and completed it is time to consider the fixed roof. My thinking on this would be that the fixed roof should be 50mm higher than the sliding roof and it should extend 100mm further over the sliding roof once it was in the locked position. You need to use the same pitch of 300mm from the bottom chord (or what ever you choose), but just raise the roof a little higher. For this I selected a 90 x 90 timber stud off-cut on each side. I fixed this to the top of the wall via several 150mm coach bolts. Strapping will also prevent the roof from flying away.

Once again I used top hat section for my purlins. This time I set them to 500mm centers. Once again ensure that these are well screwed down. I used two screws at each connection. Meaning that each purlin has 4 screws fixing it to the two trusses. The image below illustrates this point.

Once you have sheeted this part of the roof, placed the barges and fascia's into position the next thing you need to do is the roof plumbing. If you do not know how to do this get an expert in. I have worked in the building trade a long time and have worked with several people who are roof plumbers. However, this was my first single handed roof plumbing exercise. It took quite a lot of thinking to get this right. The barges must go on before the ridge cap. Each barge must be end sealed for not only looks but to help prevent water entering the roof and the building. Each barge must be as level to the roof as possible so that the lip of the barge sits inside lower corrugation. The image below shows what the barge caps should look like.

The image below shows how I went about folding the barge cap around the barge. The basic idea is that I cut the barge cap 120mm longer than the barge board. Then I cut a small section for the end to fold down and one on the inside to fold down. The 120mm long part then wraps around the two folded pieces to form a nice neat finish. A little bit of silicone here will prevent water penetration. Make sure you use paintable silicone though, as you want to paint the barges.

When this has been completed on all four barges you can install the ridge cap. The ridge must be installed about 130mm longer on each end. This is so you can cut and fold the ridge to form a weather seal. To pretty this all up you can cut and a blocking end and fix it uniformly so that the end looks like it is creating the seal. The image below shows the finished roof (all bar the gutters) but with the sliding roof open.

Now that you have the roof plumbed, you will want to install the door and locks. Hanging a door is not very hard but I can say I had not hung a door for 15 years and made a few mistakes. I used wide blocks (hinges) for the observatory door. Wide blocks are designed to be very heavy duty and will prevent most thieves from breaking the door at the hinges. Make sure also that the door is a solid core door. You want the door to present a huge obstacle for any would be thief and the door will be resistant to weather conditions.

For door locks I used Lockwood external fitted dead locks. The locks are easy to install and are what the insurance company likes to hear. Additionally, these locks are better than using an internal barrel lock. The image below shows the door installed and the first lock in position. You can see that I have installed some temporary door stops too. You will need to install these before you can install the lock. Note also how the fixed roof and sliding roof comes together. I used two different size fascia to make the roof look like it is one piece at the underside of the roof.

The final steps to lock up are the installation of any further locks; remember that you have to lock the sliding roof. I used hasp and staples with heavy locks to secure the sliding roof. Also installation of the door stops and finishing the gable ends. Security is your main issue here. Besides doing all this will keep out the weather. The image below shows the observatory at full lock up.

The next step I felt that was necessary was painting of exposed timbers. The door, fascia and outriggers needed paint on them before the winter arrived. I chose my paint and set off painting. If you have not done much painting in past, ensure you follow the instructions on the paint tin. 3 coats of paint is always best, it gives a good strength to the paint and will protect the items you are painting. Use undercoat on untreated timber, it will help protect the timber in the long run.

During this time I also installed the electrical system. There are GPO's (power points) to the pier and southern wall, a light on the eastern wall with a switch just near the door. I decided to wire the whole system via a caravan plug, which I plug into one of the house wall outlets. I will eventually have power installed to the main board of the house, but this will be costly exercise given the rock that just lies under the ground. With regard to wiring, if you are not confident of doing the wiring as per specification then get an electrician.

Your next task is to install the linings to the walls. Leaving the framing bare with wiring exposed in a moist damp environment is quite frankly very dangerous and will lead to your untimely demise. For the linings to my observatory I chose to use plastic coated form ply. It is almost water proof and very tough. It helps in the security of the observatory too. As you can see below the linings present nicely when cut very neatly. Whatever lining you choose, ensure it is water resistant or else it will rot.

The very next thing I did was install the stairs. I had found that even stepping up and down 350mm was ok during daylight but it could be a little dangerous during the night. I managed to buy a ready made set from Bunnings warehouse. I painted the stringers and then installed the unit by using two very large coach bolts through the supporting beam. Make sure this is firmly fixed into position; you are going to be stepping up and down on this a lot and with some heavy equipment.

One thing you must ensure is that the observatory does not spring a leak during a storm, in particular around the door and the roof. I bought a proprietary system by Raven for the door. It is easy to install and does a very good job of keep the water out and of course, if you have leak in the roof, it keeps the water in too! In the future I will take the seal out and install a door seal and then reinstall the storm seal.

If you have not already done something about your eaves, then it is time to get it done. Installation of the eaves keeps the birds and vermin out and will prevent dust and water from making their way into the observatory. Before I installed the eaves the dust build up was very bad. For the eaves I used 6mm plywood with button headed screws on the face. I figured that this would allow for easy access later on; and it presents an nice look.

Guttering was always going to present a problem. Two roof heights would mean two gutter heights. Gutters are very easy to install. You can buy the stop ends and down pipe outlets. Make sure you use stainless pop rivets and lots of silicone to seal the joints. To smooth out the silicone use some water with a couple of drops of dishwashing liquid. The silicone will not stick to your fingers and it will be easy to smooth it out. Also make sure you run the levels correctly in the gutters. You want the water to run out. In the image below the gutter on the left is not set correctly and will need some work to make sure it drains properly. It holds some water now, but given it is not very long the amount of water is minor.

One problem I faced with this type of roof design was the seal between the fixed roof and the sliding roof. Over a couple of months I found that the roof was leaking a lot of water, so I set out to solve the problem. What I found was that the sliding roof ridge cap has a slight bow in it and this results in water draining towards the fixed roof. I decided that I could bend up the ridge just a little and I reshaped it near the very last corrugation of the roof. This prevented water from simply running into the observatory and all over the floor. Then I made a flashing that was flexible and would prevent water splashing into the observatory. I did this by buying a plastic flashing and screwing onto it a rubber flap. I added heaps of silicone to the joint between the flap and plastic flashing so that water could not seep down the joint and make its ways into the observatory. The resulting flashing and modifications to the the ridge cap seem to have stopped water entering the building and yet allow me to open the roof easily. Time will of course tell how well this works and I can always make more modifications should some water still be entering the interior.

This is how the building looks in June 2009. Still some jobs that need attention. In the coming month I hope to have the building fully completed. Stay tuned for more updates.

After a short break the next thing I completed was the eave linings and then several weeks later I installed the carpet. The eave linings seen second image below is made from 6mm plywood. It is light and easy to care for. Just cut these to size and screw the pieces into position. The carpet is marine grade and therefore able to be subjected to water. It is easy to lay and using spray glue is the easiest way of fixing it into position.

After the carpet installation I set about installing the outside skirting. The idea is to prevent the vermin and snakes from entering the observatory and it does make the structure look finished off. In the image below you can see the skirting installed. To do this, you will need to take out the screws at the bottom of the sheeting and install a Z flashing. The flashing prevents water from entering the building by seeping upwards and it allows you to place the corrugated iron under it and give a neat finish. As a preventative measure I dug a trench about 3 inches below the ground level and cut my sheets to this height. I then simply back filled the sheets and this will act as a natural barrier for the wild life.

Once the sheets are installed I then flashed off the corners. Just use some galvanized corner mold, cut and folded the top lip and then screw it onto the sheet. Try to be mindful of over screwing the molding. It causes what is called oil canning. I have slightly over screwed the molding shown below but it still looks reasonable despite this.

This image below shows the observatory with its new garden, which has purple fountain grasses, a grass tree as the center piece and out of view is an Echium.