Monday 14 January 2013

Awnings and Bastard Valleys

By Christmas we had almost done as much of the walls as we could without putting the awnings on. Originally the delay was getting the awning brackets on, but this was easily solved after getting  a few quotes from steel fabricators. The brackets were plasma cut to the engineers design from 3mm Galvabond steel by WH Williams at Silverwater.  For added protection from rust I sprayed the cut edges with Cold Gal. I then sought a builder to do the carpentry work but could not find anyone willing and available to do the work. I sought advice from a carpenter friend and with the promise of assistance, resolved to put the awnings up over the Christmas break. Due to other commitments the assistance went from in person to telephone help. I was on my own, so I consulted Alan Staines book, “The Australian House Building Manual". It showed some clear line drawings of what a valley should look like.

Friends from my son’s pre school stayed on site with us for a few days after Christmas for a working holiday and Will go roped into assisting me with the awnings. The purpose of the awnings is to provide shade to the north side of the house in the warmer months, as well as to provide a sheltered area under which to enter the house through the glass sliding doors and to break up the large north facing walls and visually anchor the house to the ground. The awnings too some thought but were not beyond our capacity.

We started with the awning on the back pavilion. Although Will did not have a building or carpentry background he took a thoughtful and practical approach to things and was helpful to bounce ideas off. The attachment of the brackets was straight forward, once I worked out the correct position from the ridge on the hall, taking into account the depth of the batten to go on top of the awning rafters and the width of the hemp wall, so that the roofing on the awning will line up with the roof of the hall at the ridge and eaves.  This meant I had to build a bastard valley where the two roofs joined. The awning rafters were bolted onto the brackets and the brackets bolted to the studs at 600mm centres. Because some of the studs were only held between the sliding doors and upper windows, we reinforced these studs where they met the window sill with a metal plate (cut from spare brackets because we reduced the length of the awnings), to prevent the stud from pulling out from the sill, given the extra weight on it from the awning. 

Awning rafters attached
A job well done
 Bastard Valley really is the technical term for the valley between two roofs with different pitches and it lived up to its name.  We worked out the line for the valley rafter then, to complicate matters, had to remove part of the hall roof, that had temporarily been put on to give us a dry space to work under, and remove some of the hall battens and shorten some rafters, while still maintaining the rafters to attach the ceiling lining to. To do this we left in one of the hall rafters, which would otherwise have crossed the valley rafter, and ran the valley rafter from there, which involved cutting the valley rafter at a compound angle (angles in two different directions). After some head scratching as to what the angles were and then how to get the saw to produce them, we cut the angle correctly and the rest of the awning rafters were cut to fit. The following day a little bit of adjustment (by loosening the bolts, moving into place, and re tightening) was needed to one or two of the rafters to get them to line up at the right height with the timber fascia, which was also used as the final batten. The rest of the battens will ho on after we have hemped the wall above, by temporarily leaving them out we can duck through the rafters to put up the form work. We will place the hemp mix from the inside. 

Newly installed bastard valleys
Valley rafter joins timber fascia
 A few days later my partner and I tackled the other side of the awning. It was definitely easier but there was also more swearing as little things went wrong. We had some luck, the metal strap bracing looked like it would get in the way of the brackets, but amazingly the correct spot for the bracket fell between the cross pieces of the bracing. We used leftover triple grips where the awning rafter intersected with the hallway top plate. The first awning we nailed the valley rafter to the awning rafters, but for the second part of the awning used batten screws. Batten screws are so strong and with the impact driver easy to put in. They are me new best friend.

Lucky bracket location between the bracing
Second side of the back awning done
We are now 1/3 of the way through the awnings. Just the sections on the main and front pavilions to go.
More awning rafters ready to go up on the main pavilion


  1. Thanks for sharing your experience with these lovely images. The detailed information will help many homeowners in making their living space more comfortable and energy-efficient without carrying out any major home renovation. However, one must decide the design, size and style of residential awnings based on the prevailing weather conditions of his area.

  2. Thanks for posting these DIY tips. Homeowners can now make their own awnings with the help of these detailed and comprehensive information. Surely enjoyed reading this write-up. Keep it up!

  3. Hi there! Nice stuff, do keep me posted when you post again something like this! outdoor blinds Melbourne

  4. Your blog has some excellent stuff. Additionally, I have some helpful information about commercial awnings chicago, which I believe must quite helpful. commercial awnings chicago