Browse Forums General Discussion Re: Has anyone rectified slab heave successfully 283Jul 21, 2014 6:39 pm 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: Has anyone rectified slab heave successfully 291Jul 26, 2014 12:04 pm Interestingly, in this thread I have found several people mentioning that AG drains was in fact what actually CAUSED their slab heave. And ag drains are what is usually recommended to avoid water ponding near slab foundations. So do they work or are they simply dangerous? And now that I think about it I don't even understand how can they work? It is a pipe in a trench filled with crushed rock with holes in it. The idea is that the excess water will flow away through the pipe. But the pipe sits on top of 2-3 inch of gravel underneath it(otherwise it will clog up very quickly). Where will the water go from under the pipe? Right into the ground? So if you installed ag drain did you just build a good deep conduit for water to go right under your slab? Somebody mentioned that after getting affected by slab heave caused by ag drains installation they will be replacing them with spoon drains. Are spoon drains much better solution than ag drains? Re: Has anyone rectified slab heave successfully 292Jul 26, 2014 12:56 pm tkormich Interestingly, in this thread I have found several people mentioning that AG drains was in fact what actually CAUSED their slab heave. And ag drains are what is usually recommended to avoid water ponding near slab foundations. So do they work or are they simply dangerous? And now that I think about it I don't even understand how can they work? It is a pipe in a trench filled with crushed rock with holes in it. The idea is that the excess water will flow away through the pipe. But the pipe sits on top of 2-3 inch of gravel underneath it(otherwise it will clog up very quickly). Where will the water go from under the pipe? Right into the ground? So if you installed ag drain did you just build a good deep conduit for water to go right under your slab? Somebody mentioned that after getting affected by slab heave caused by ag drains installation they will be replacing them with spoon drains. Are spoon drains much better solution than ag drains? Spoon drains are to get rid of the surface water from heavy rain Ag drains are for sub soil drainage. You are right, they too can cause slab damage. Bottoms of AG trenches must be graded in direction of flow to avoid drain trenches becoming underground reservoirs of water. Drain should be laid directly on freshly scraped firm bottom of drain trench then trench filled with crushed rock. If it's done correctly bottom of drain=bottom of trench and all water will quickly flow away. AG drains should be as far as possible away from slab edge. For effective drainage management of "H" or "P" class sites you will need both spoon drain and AG drains 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: Has anyone rectified slab heave successfully 293Jul 26, 2014 3:19 pm Agi drains do work to some degree. If you dig a trench in natural ground water will collect in it. Any disturbed ground water will flow into it compared to natural ground. Water finds the path of least resistance so even a trench with no pipe or crushed rock will collect water. Most drains a poorly designed and often poorly constructed if they are founded in the wrong soil profile then they are not going to work.
I prefer a cut off drain which is much more effective This is a typical design but has several variations. The two critical points with this design are the founding soil (not fill or topsoil) but natural clay and the plastic membrane on the house side of the trench. The extra benefit of the plastic under the concrete is you can seal it to the brick wall there by eliminating another problem talked about in this thread and that is rain running down the wall between the edge of the concrete and onto the footings. Also this design will stop sub surface water from the neighbouring property getting under your slab. Re: Has anyone rectified slab heave successfully 294Jul 27, 2014 3:16 am insider Looks like the concrete wasn't properly vibrated.Can you get some info from who ever did the pre pour inspection to make sure the reo was placed correctly. The building surveyor.s report came back with no issues. Re: Has anyone rectified slab heave successfully 295Jul 27, 2014 5:54 am The link below is about slab edge dampness and water ingress but note that it is dated 2005. http://www.concrete.net.au/publications ... mpness.pdf EDIT: The next link discusses flexible pipe joints. http://www.stormplastics.com.au/files/P ... -10-06.pdf 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Has anyone rectified slab heave successfully 296Jul 28, 2014 9:22 am Hi All, It looks like we are going to have to build the garage close to the boundary of our block in order to line up with the cross over. Regarding protecting our slab from heave, is a 150mm a good enough offset from the side or should we opt for a bigger offset? Thank you Re: Has anyone rectified slab heave successfully 297Jul 28, 2014 11:39 am joea Hi All, It looks like we are going to have to build the garage close to the boundary of our block in order to line up with the cross over. Regarding protecting our slab from heave, is a 150mm a good enough offset from the side or should we opt for a bigger offset? Thank you That question should be directed at your slab design engineer. 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: Has anyone rectified slab heave successfully 298Jul 28, 2014 11:44 am building-expert joea Hi All, It looks like we are going to have to build the garage close to the boundary of our block in order to line up with the cross over. Regarding protecting our slab from heave, is a 150mm a good enough offset from the side or should we opt for a bigger offset? Thank you That question should be directed at your slab design engineer. Oh I assure you it will be. I thought I would ask people on here with experience in the matter. After all, that is what forums are used for right? Also, slab design engineers have signed off on many slabs that are currently having major issues. That's why this topic exists. Appreciate any information/advice provided. Thanks. Re: Has anyone rectified slab heave successfully 299Jul 28, 2014 4:34 pm Drainage is difficult with such a small area to work with .I do know some engineers have recommended deepening the edge beam along the garage side instead of drainage but if you have a waffle that's not possible.Is your neighbours crossover on the same side as yours ?if it is then there is a chance that their garage will up against yours providing some protection from the weather. Re: Has anyone rectified slab heave successfully 300Jul 28, 2014 4:56 pm insider Drainage is difficult with such a small area to work with .I do know some engineers have recommended deepening the edge beam along the garage side instead of drainage but if you have a waffle that's not possible.Is your neighbours crossover on the same side as yours ?if it is then there is a chance that their garage will up against yours providing some protection from the weather. Hi insider, I see, what would you recommend as a minimum distance to allow for adequate drainage. I know it is a small span compared to the remainder of the house but still would like to consider the optimum location for the house. Unfortunately, PD has clearly said that they only use waffle slabs unless the engineers they use say otherwise. Our Neighbour's driveway is on the opposite side. I have been looking around some new estates lately and all the garages seem to either be pushed out to very close to or directly on the boundary of the block. How can the home owner ensure they have correct side drainage when the slab marks the edge of the block of land?? It's not their land, your neighbour can decide to plant something there or even dig a hole and let water pool up in that area... Doesn't make sense. Hi All, we are starting to think of building with Masterpiece Builders in Victoria, has anyone had any feedback or experience with them 0 13958 Hi we are looking to talk to people who have built with them recently. We have signed mid range built contract but identified that a lot of things are not included.… 0 772 I work with owner, he/she is my man on the ground and I instruct them when to visit the site and take photos and I have other tools in the bag. 4 15564 |