Browse Forums Building Standards; Getting It Right! 1 May 14, 2015 4:27 pm Hi, 4 years ago a builder replaced a joist in our house, on top of which they put a waterproof deck. They replaced a joist because the previous one had rotted due to a water leak. The waterproofing has now failed and I believe it is down to the new joist they put in. Attached is a photo of the joist. http://postimg.org/image/utslpzu6h/ The notch is mid span, on the bottom of the beam (i.e. under tension), and 70mm deep (the joist is 150mm deep). My opinion is that they have notched it too severely to accommodate an existing power cable. Can you let me know your opinion and whether you believe I have a case for them to replace it and the waterproofing that has failed due to this joist not being sufficiently strong due to the notching? Many thanks Re: Joist notching question 2May 14, 2015 4:33 pm Definitely too much of a notch. A proper tradesman who understood what they were doing would have drilled a hole in the centre. See http://www.anewhouse.com.au/2015/03/con ... er-frames/ 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: Joist notching question 3May 14, 2015 5:23 pm Yes, the notch is way too big for that cable resulting in a loss of strength to that beam however it has nothing to do with the waterproofing failing. If the span calls for a 150mm timber beam then you can drill minor holes through which will not diminish its strength. Notching it out 70mm has severely weakened it and should be replaced. If this is how they do their work I am not surprised your waterproofing to the deck has failed. Stewie Re: Joist notching question 4May 14, 2015 9:23 pm Thanks for the replies. My reasoning for thinking it relates to the waterproofing failing is that the weakened joist will flex too much and over time this movement will crack the screed upon which the waterproofing is laid. Not a concrete argument I know, but it seemed logical with my limited knowledge... Is it reasonable to say that the additional flex by this structurally unsound joist could cause the waterproofing membrane to fail (ie break, split or shear)? Re: Joist notching question 5May 15, 2015 9:06 am In a word no. Nearly all waterproofing membranes are flexible and are usually a material base or cloth especially over joins in floor sheeting then a thick painted compound applied over the top in two to three coats. This forms a thick but flexible waterproof layer that should easily handle any movement in the floor below - expansion and contraction plus any sagging of the floor itself. The screed is just a base that the tiler lays so he can get his falls right or to correct any inconsistencies in the floor levels. As I said before looking at the amateur way they have notched the joist I'd say they have also done an amateur job of the waterproofing. If they did the waterproofing only four years ago then it should be covered under the builders warranty to fix it - plain and simple. Stewie Re: Joist notching question 6May 15, 2015 9:36 am Thanks Stewie, Given my knowledge is limited to argue the relevant point (as illustrated here) I think it may be best I get an inspection done so I (or the inspector) can argue the relevant points with Fair trading. The builder has argued the waterproof has failed due to: 1 - Inherent structural issues 2 - General maintenance 3 - Retro fitted items to the deck area and surrounding handrail. Note, the retro fitted items are flower pots and a bench, all of which are free standing Item 1 I'll argue they themselves have created structural issues with their notched joist and, as they opened up the deck to assess the structure, the fact they chose not to do any other works to the subfloor means they accepted the structure was sound to put their work upon. Item 2 I don't understand. It's a deck, which gets pressure washed every couple of months, what other maintenance is there I should be doing... Item 3 Is just funny. If the deck can't support furniture then it's not sound. Never-the-less, I need to be prepared for an argument with them through Fair Trading, and an unqualified person like me will have limited sway if the builder is better informed about what's acceptable than I am. Cheers Steve Re: Joist notching question 7May 16, 2015 8:32 am Let us know how you get on. I'm always astounded the reasoning/excuses some guys have. A decent building inspector will run rings around these clowns if that is the best they can come up with. Stewie Re: Joist notching question 8May 16, 2015 8:02 pm by the looks of it, it could be said this joist acts as a pole plate not a joist. It looks to be bolted to the side of the house also. This changes the situation a bit. Also, being the end joist as such it takes less load (if i'm reading it's position right. Yes it could have been done a bit neater, but seeing as it appears to be bolted to the house it runs along I doubt you have any flex in it Re: Joist notching question 9May 16, 2015 8:04 pm bashworth Definitely too much of a notch. A proper tradesman who understood what they were doing would have drilled a hole in the centre. See http://www.anewhouse.com.au/2015/03/con ... er-frames/ I'm going to guess the wire was there first which is why it was notched. They likely were avoiding having to get an electrician to cut and re join or re run the wire Re: Joist notching question 10May 16, 2015 8:43 pm Hi 33amc, When they put the new joist in its actually 2 joists they put in as they didn't want to open up the entire area to put a joist in. The 2 joists are shorter than the length required, each is pushed in opposite directions until it touches the end support and then bolted together. Both joists are notched, but only one end of each joist is actually supported. The bolt you see is tying the new joists to the old rotten joist (which is a bad idea too as the bolt goes straight through an area of rot). The new joists are in the middle, not near the walls. Thanks Re: Joist notching question 11May 17, 2015 3:48 pm This is the other side of the bolt: http://postimg.org/image/4xj289173/ as you can see it's tied directly into rotten wood on the existing joist Assuming you've modelled the TB8, TB10, TB12, TB2 & J1 joists/LVLs there, it appears as per drawing to me. There maybe should be an additional J1 between TB10 and T12 if… 3 31853 Seconded; we just used these last weekend to build a small deck. They worked perfectly as we have bluestone in the area where we wanted to build so digging down was not… 8 9084 1 10137 |