Hello , the example you have given is coupled roof, since the roof do have support between the rafters. but the notes you have mentioned is for non-coupled roof. I am a bit confused here. Thanks for the Video. it is really helpful
Hi June, the first half of the video looks at Non coupled roofs and then the second half of the video looks at the coupled roof. The diagrams in the first half of the video show the top plate in position, maybe this is making you think that the roof is coupled however this is not the case. Hope this helps
These are really great, but what I don't understand is, why would anyone other than the engineer need to know these? Doesn't the builder just follow the engineers specifications anyway?
Hi mate, this is actually in the scope of what a builder can do however these days with the level of complexity of some of the projects and the want to transfer liabilty to others, yes it is frequently left to the engineer to work out. On small renovations, extensions, pergolas etc it is generally not work the extra money for an engineer so the builder can use it then. Hope this helps
abslutely not. A good builder will know more than just banging stuff together and reading a plan. No wonder trades have lost there beauty these days.The whole why should i do it....and then you guys are the first to bag out everyone else when shit goes south.
haha! I totally had a brain fart. All this is new to me..so I was watching the skillion part..and in other videos you talked about half span which some people write 1/2 Span in their videos..so when I got to the skillion part, I read it as (Span 1/2) like "Span half" thinking you meant half span..but you meant Span 1 (span one) / (divided by) 2. haha! whoops.
Hi buildsum, your videos are very helpful thankyou for your efforts and time to teach us, i have one question however as there’s still one more type of roof that wasn’t mentioned and thats the cathedral roof in where the rafter is sitting on the wall, with no ceiling joist, held by collar ties towards the upper third of the roof with a ridge beam, what calculation would be used, I can provide photos if you’d like to your email maybe to make myself more clear, thankyou so much
Hi Abdul, i would think that this would fit as a Coupled Roof - No purlin similar to the one shown at 3.26min. The ones i have shown in this video are as per AS 1684.2 which is the Timber Framing Standard for non cyclonic areas in Australia. If what you need is not covered by the standard then you will need to get a Structural Engineer to design a system that will work for you. Hope this helps.
@@Buildsum yes, what I’m after isn’t covered in the bca like you said so there are roofs that a Carpenter can’t construct without engineer involvement, thankyou , much appreciated
Hi Buildsum, Absolutely love your videos and explanations. Can you help me with clarification please? At 5.25 Coupled roof with underpurlins & ridge support; Span 1- ridge takes half of the load towards underpurlin- (that equals 1/4 of span 1). Then A takes the load from half way up toward underpurlin (that equals 1/4 of span 1) plus add span 2. Does that mean that RLW at purlin is total of 1/4 of span 1 above it plus 1/4 of span 1 below it? ie half of span 1? ie if span 1 is 6 mts in this situation and I had to select a purlin size- the RLW applicable for the purlin would be 3000? Or have I got this muddled up? Thanks in advance.
Hi Robin, thanks for your comment and sorry for the delay in getting back to you. The RLW in this case is just Span 1 / 4 +Span 2. So if Span 1 is 6m then the RLW will be 1.5 - Span 2. Hope this helps.
Hi Buildsum, for a layperson these are a fantastic video series. At 4.30 in this RLW video there is an underpurlin shown but the RLW as given for support A appears to be for 1/2 of span 1 plus the overhang 2. As if the underpurlin under span 1 isn't providing any effective support at midspan rafter. Yet further on when the ridge support is shown at 5.20 span 1 loading is correctly divided into 4 parts (assuming underpurlin is at rafter midspan). Similarly, at 4.30 shouldn't the span 3 be divided by 6 as is the case further on? Can you please confirm which is correct? I'd also like to suggest that the load on on the span 1 underpurlin (at rafter midspan) would be 3/4 span 1 and 1/6 span 3 (if underpurlins are evenly spaced). Similarly each of the underpurlins under span 3 the loads could be easily solved. Look forward to your comments.
Hi Peter, In the first example at 4.30 it is not the purlin that's not providing support but rather the ridge. These formulas are as per AS 1684 Timber Framed Buildings which I'm sure were worked out by smarter people than me and are the ones that we need to use regardless of whether we think they are correct or not.
ive worked out my RLW for a carport but im trying to find what beam i can use using the span table ( single span flat or skillion with no overhang 5.4m roughly maybe a little less) are you able to help me?
I thought for the Truss roof, it's being supported at A and at the ridge support, so the RLW I thought would be (Span1 / 2)+Span2. I know you calculated differently - how come you add both Span1 and Span3 if it's supported by the ridge support?
Hey Buildsum love you’re videos. Do you know how to find the RLW for the hip end of a hip roof? Do I use the crown rafter and calculate it like a non coupled roof? I am making a large opening in the hip end load bearing wall so need to know what size lintel is sufficient. Thanks!
@@Buildsum great thank you! My trainers at trade school (Trades Institute Victoria) use your videos in class all the time. Such good content thanks for sharing.
Hi, the RLW is a measurement that is used in AS 1684, Timber Framed buildings, to determine the amount of load a member is required to carry. Hope this helps.
actionjessie The RLW applies to the whole roof not just a particular area so if you use the formula for a trussed roof it should give you the RLW that you need.
