Browse Forums Building Standards; Getting It Right! 1 Aug 29, 2014 12:27 pm We have had some correspondence with our builder recently on the subject of our wall bracing which isn't entirely consistent with the wall bracing plan prepared by the engineer. The builder has now sent us the framer's pre-nail certificate detailing the wall bracing used in our home. The first thing that intrigues me is that the pre-nail certificate has a wind classification rating on it but I can't find any wind classification rating on our building permit plans. Is there supposed to be one? The second thing that is odd to me is that the wall bracing on the pre-nail certificate doesn't correspond in any way with the engineer's wall bracing. The engineer has specified the following (A being diagonal strap braced walls and B being ply braced walls): 9 x A-2700 1 x A-1800 1 x B-3000 1 x B-1450 1 x B-1200 2 x B-1000 1 X B-960 1 x B-900 1 X B- 810 1 X B- 800 1 X B-700 1 X B -610 2 x 600 Power Truss walls The pre-nail certificate specifies this: (though there is no detail as to where the bracing is to be placed) Bracing for wind blowing direction A (N/S) 3 x 2.7 Double diagonal tension braces 3 X 2.4 " -0 1 x 1.8 " -1 3 X 0.9 3.4 kN plywood 5 x 0.6 3.4 kN plywood-3 Bracing for wind blowing direction B (E/W) 3 x 2.7 Double diagonal tension braces 4 X 2.4 " -2 2 x 1.8 " -3 5 X 0.9 3.4 kN plywood 4 x 0.6 3.4 kN plywood-0 Looking at the photos we took of the frame, the bracing seems to be more consistent with the engineer's specifications except that the Power Truss walls are ply and there is no B-3000 bracing - in fact, where the B-3000 bracing should have been there is nothing! I also can't find any difference in the diagrams for the double diagonal tension braced walls-2, -3 etc. I have two questions for anyone who has read this far.... is it normal for framers to ignore engineering and make up their own wall bracing plan? And how did this pass the frame inspection??? Re: Wall bracing changes 3Aug 30, 2014 5:45 pm Cant say anything about design of wall frames as my timber design experience is limited . . . but as a civil engineer I have always designed things by planning how I would build them. At least 50% of the time a contractor will come up with a different design that suits the equipment they have got. As long as the different design meets the overall objectives I have been quite happy for the contractor to use their design. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Wall bracing changes 4Aug 30, 2014 6:27 pm Hi bashworth, Thanks for the reply. I presume the contractor would discuss the matter with you and tell you why the changes are better, wouldn't they? Or would they? Or do they just make changes without consulting you? Re: Wall bracing changes 5Aug 30, 2014 6:30 pm Its not uncommon for braces to be moved for various reasons. The plan may show it at one end of a wall and on the outside, if the house has full cladding we will move it inside so there is not the need to pack out the entire ext wall. It can be the case when moving it inside it may not fit between the corner and window so its moved to the other end of the room. The main thing is all bracing shown on the plan has to be included in the house. Re: Wall bracing changes 6Aug 30, 2014 7:01 pm Liliana Hi bashworth, Thanks for the reply. I presume the contractor would discuss the matter with you and tell you why the changes are better, wouldn't they? Or would they? Or do they just make changes without consulting you? In my case I would expect to be consulted but the consultation might just be an exchange of letters (or Emails) The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Wall bracing changes 7Aug 30, 2014 7:22 pm Thanks for the info Mcgilla. From the photos the bracing is more consistent with the engineer's plan than the pre-nail certificate except that there is no bracing on the kitchen wall which was supposed to have been 3000mm ply bracing and they have not used the Power Truss steel bracing in the nib walls. They have said that because they didn't use the steel bracing they have put in more ply and diagonal braces but this doesn't tally with the photos. The pre-nail certificate specifies 16 diagonal braces but there are only 11 evident in the frame photos. Bashworth, in this case the builder doesn't seem to have been aware that any of the bracing had been changed since he had to go back to the framing company to investigate??? So he certainly didn't communicate with the engineer. As far as I know there was no communication with the engineer from the framing company but I will need to confirm that. Re: Wall bracing changes 8Sep 22, 2014 11:53 pm Hi Liliana, About the design wind speed. There used to be various speeds 28m/s, 33(?) m/s and 42m/s for no cyclonic zones. Now I believe the speeds are 34m/s (N1), 40m/s (N2), and 50m/s (N3) probably revised upwards because of the increase in frequency and ferocity of storms/wind gusts. N2 winds need special care for bracing and also tie-downs. It usually means that you are in an historically windy area or one of the first few (unprotected) houses in the area or unprotected on the whole of the wind origin side - facing a lake or something. Hope this helps a little, cheers, Leonardo_23 Re: Wall bracing changes 9Feb 02, 2015 8:24 am Can anyone tell me what effect insufficient bracing would have on a house? Would it simply fall over in a high wind or are there more subtle effects? Would it mean that a wall that is basically windows and glass doors would be under extra pressure leading to movement and cracking at the corners? Or is the latter purely a foundation movement issue? Re: Wall bracing changes 10Feb 02, 2015 3:20 pm Basically in a timber framed house the timber frame (with its bracing) provides restraint against horizontal forces on the external walls. Often the biggest horizontal force is Wind. You may recall a couple of years ago 2 people were killed in the Melbourne CBD when an unrestrained wall was blown over, so the forces can be considerable! In the case of a house inadequate bracing may result in some movement (and creaking) without necessarily failing. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Wall bracing changes 12Feb 02, 2015 8:26 pm It's not uncommon for prenailed frame and truss companies to alter bracing layouts. Most of the time I used to follow the engineering where a bracing layout was provided unless there was a very pressing reason not to. Changing it cost time and also meant we assumed responsibility for the design, neither of which was something I wanted to do as a manufacturer. Many plans (even most!) were provided without an engineers bracing layout and thus wherever possible we would work it out ourselves. Sometimes it was not possible and we would bounce it back to the engineer. Re: Wall bracing changes 13Feb 02, 2015 8:55 pm Ok, Go to your bracing plan. Is should show required values in both directions. This is calculated on the area of your house the wind hits times the wind pressure for your region. This comes up with a value in "Kn" Now, also on the same page it will demonstrate the bracing intended to be applied, and it will give a value for how much all the suggested bracing applies. There is no formula for exactly where each bracing panel must be placed, the standard simply states it must be placed evenly and at not more than 9m apart. This does leave room for flexibility, and panels could be moved as long as they are in the same plane and the bracing remains evenly spread. If I was to move a bracing panel I wouldn't bother wasting anyones ear on the matter. Further to this, This amount and placement of the bracing panels is one of the main things the certifier will check. If you are asking questions of anyone, I would be asking what the certifier assessed the design against. Now, It is allowable for framing companies to change any framing elements of the design as they will provide a certificate against the design of what ever they do. Also, If there ply Quoted as Achieving 3.4kn/m, this is a very inefficient brace. As I started to say on the other topic, Ply will typically achieve 6kn/m. The difference is it needs to be nailed 50mm apart on the top and bottom edges instead of 150mm apart. If your ply has been nailed in the pattern that achieves 6kn/m, you will need less panels as the total required will be achieved with less panels. Now, To take it one step further, the plasterboard on your walls can also be counted as bracing, but it can not make up more than 50% of the required. Most designs don't get that cheap where they remove half the bracing, but it is allowable to do so If you wanted to post a pic of your bracing plan or PM me one feel free. Andrew Re: Wall bracing changes 15Feb 03, 2015 11:09 am Hi Liliana Wind speed is sometimes noted on soil test report (I have seen it few times) Insufficient bracing is always a concern not only because of potential failure in high winds but also because of reduced rigidity of the home manifesting in sway and possible internal plaster cracking. Contractually builder is not allowed to vary works without your consent (unless variation is forced on by events outside builder's control). That means he cannot change bracing (or anything else) that is shown on engineering or other plans. The proper procedure is to issue you with a variation request, noting why the change is required, cost and time implications, review from the engineer and acceptance from a building surveyor and ask for your consent in writing. If variation is accepted then drawings are amended, re stamped revisions noted on drawings dated and re issued to all relevant parties. I am a QS and have worked on major hospital projects(with a leading Victorian builder) with hundreds of variations and this is how it is done (properly) I used to get a signature of receipt from each subbie to whom I given amended drawings. There were no disputes who got what and when. As building contractor myself I was always aware that if I changed anything it would be my neck on the chopping block if i did not follow the procedure. Your builder did not follow proper procedure. No excuse! Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: Wall bracing changes 17Feb 03, 2015 9:35 pm [quote="building-expert"] Contractually builder is not allowed to vary works without your consent (unless variation is forced on by events outside builder's control). That means he cannot change bracing (or anything else) that is shown on engineering or other plans. Even slide a panel to a different location? If someone had to wait for 15 emails and 3 rubber stamps before making such a minor alteration then this would people a lot of time and money in the residential game. You can't apply the inefficient way a commercial project runs to a low cost house build scenario. I do however agree that the removal of the power braces should have been at least discussed before removing, but to try and eliminate common sense and good practice in lieu of having a round table meeting every 5 minutes over the petty things is something that just doesn't happen. Don't forget that drafties, and engineers make errors too. I see them all the time. I had one the other day where a brace panel was drawn over a door way, I instructed my guys where to move it too and the job went on. I can't wait even 1 day to get rubber stamps flying, my guys are else where by then. Some things are just obvious that a slight change is needed, but any major changes that affect the look or use of the house should definitely be discussed with the client Re: Wall bracing changes 18Feb 04, 2015 7:30 am insider your particular rating would be N1 Thanks for that info insider. building-expert Wind speed is sometimes noted on soil test report I've had a good look and can't find anything noted anywhere but I've now written to the engineer to ask him what values he was working off. I have a structural computation sheet but it doesn't seem to mention wind values. 33amc Even slide a panel to a different location? Everybody does make mistakes and I'm sure we would all agree that such minor alterations are not worth wasting paperwork on. But context is everything - I'm fairly sure you wouldn't waste somebody's time ringing them at all hours of the day or night to complain about matters such as (and I'm picking one entirely at random here) the fact that the building designer has asked you to put the wire racks at the bottom of the pantry cupboard and the trays at the top. Is this really worth an hour of a builder's time? And, assuming it is, why not slip into the same conversation - "oh, by the way, I removed your Power Truss walls - just for your info". This kind of thing is why I don't feel inclined to cut the builder any slack. The other aspect to this, which was only brought home to me yesterday as I was examining the new bracing layout, is that a previously unbraced wall is now braced - a wall we were intending to knock down a couple of years down the track. Had we been working off the engineering drawings we would have had a bit of a surprise. So if I had to do this over again I would probably make sure my bracing and my plans actually reflected each other while we were still at the building stage and I would also make sure I wasn't paying for bracing to a higher wind level than I was actually getting. Re: Wall bracing changes 19Feb 04, 2015 10:35 am In the end it comes down to builder's promise to do for a promise to pay. In promise to do builder warrants to build in accordance with plans and specifications, that is the contract. Now someone has come with a view that in the interest of expediency (for the convenience of the builder) it is OK to go to town and make changes. I am not buying it. Interfering with approved engineering design in my view is a serious matter Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: Wall bracing changes 20Feb 04, 2015 10:49 am Agree with b-e. With structural changes, how would the client ever know and where do you draw the line? The line is what the contract states and is it even remotely desirable for a builder to be changing an engineering specification without consultation and notification in any case? There seems to be a dose of arrogance in the mix in this instance. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Hi all, Not sure if this is a good place for this question but I guess we'll find out! I'm a novice, building a modular room inside my garage/shed and need to create… 0 1862 I engaged my builder in December last year and we’ve been working on preliminary drawings for last couple of months. I got a call from the salesperson this morning… 0 600 Thank you again Simeon.. I will call my certifier for that. Have a good day 4 5197 |