Browse Forums Building A New House Re: House slab on H2 in 4 days 11Jun 17, 2020 3:30 pm alexp79 Correct me if I am wrong, but you can still use shallower footings even if movement is above 100 mm due to trees or extremely reactive soils, as long as the slab is stiffened enough? E.g. in Northern countries they often use 250-300 mm very well stiffened monolithic slabs (ie you virtually get slab-wide footing, stiffened with 2 layers of 12 mm bars forming 200x200 cells) on extremely reactive clays and they have freezing factor over there too! Why do you think builders won't be able to do controlled fill? It is not really that hard and I have done it for my house slab (following layered compaction technique and with radioactive compaction testing). 32 mpa concrete is for extra strength in this particular case, it may not be a specific Cupolex requirement per se, in fact slab on top of Cupolex can be even 60 mm slab with 25 mpa concrete. You can use monolithic slabs which needs significant more concrete and it is different then to waffle and Cupolex? this is beneficial when we are dealing with extreme movements, with existing trees I believe it is cheaper to do piers where required as you have settlement issues and not heave problem unless you are removing the tree. They will do control fill if you educate them and supervise them, ask Builders what is the difference between rolled and controlled fill, volume housing builders which do majority of work, do not have understanding of it and they never do it, they never found the edge beams of waffle slabs into controlled or natural soil, this is partially their fault and partially engineers who donot detail their slab design properly and leave it to builder to put a waffle slab edge beams on rolled fill, you just need to check some of the new build houses in Melbourne to see houses less than 3 month old with cracks. In an industry where we can't design and build a simple residential slab properly (volume housing mainly) from Australian Standards, I wouldn't suggest introducing more complex systems, you are technically competent but majority of home owners are not. Re: House slab on H2 in 4 days 12Jun 17, 2020 3:52 pm Structural.Review alexp79 Correct me if I am wrong, but you can still use shallower footings even if movement is above 100 mm due to trees or extremely reactive soils, as long as the slab is stiffened enough? E.g. in Northern countries they often use 250-300 mm very well stiffened monolithic slabs (ie you virtually get slab-wide footing, stiffened with 2 layers of 12 mm bars forming 200x200 cells) on extremely reactive clays and they have freezing factor over there too! Why do you think builders won't be able to do controlled fill? It is not really that hard and I have done it for my house slab (following layered compaction technique and with radioactive compaction testing). 32 mpa concrete is for extra strength in this particular case, it may not be a specific Cupolex requirement per se, in fact slab on top of Cupolex can be even 60 mm slab with 25 mpa concrete. You can use monolithic slabs which needs significant more concrete and it is different then to waffle and Cupolex? this is beneficial when we are dealing with extreme movements, with existing trees I believe it is cheaper to do piers where required as you have settlement issues and not heave problem unless you are removing the tree. They will do control fill if you educate them and supervise them, ask Builders what is the difference between rolled and controlled fill, volume housing builders which do majority of work, do not have understanding of it and they never do it, they never found the edge beams of waffle slabs into controlled or natural soil, this is partially their fault and partially engineers who donot detail their slab design properly and leave it to builder to put a waffle slab edge beams on rolled fill, you just need to check some of the new build houses in Melbourne to see houses less than 3 month old with cracks. In an industry where we can't design and build a simple residential slab properly (volume housing mainly) from Australian Standards, I wouldn't suggest introducing more complex systems, you are technically competent but majority of home owners are not. My point re monolithic slabs is that if Cupolex engineers claim that they can achieve similar stiffness and with their system, then it should be more or less inter-replaceable? Although mono slabs require more concrete and reo (btw, reo costs can be significantly lower than conventional slab if Helix Steel steel fibers are used), they also require significantly less ground works (excavation of beams/extra set outs) and form work set up efforts when comparing to conventional rafted slabs, plus you can also sum up concrete and ground works required for excavation of the piers too in order to run a proper side by side costs/effort comparison. In the end of the day, considering the cost of labour, you might end up with not so significant difference when comparing to conventional rafted slab on piers. 20 extra cubes of concrete cost only $4-$5K which is what you roughly pay for 2 extra days of excavation and form work laborers, plus piers will add up even more. Let's also keep in mind that waffle pods are not really recommended for highly reactive soils. I am not totally against piers as long as they are properly inter-connected to the underlying slab to prevent soil getting under the piers when slab lifts off due to soil movement or at least protective flexible caps are used. I don't think a lot of builders/engineers following that. But yes, I completely agree with your point that we just can't really push new technologies to mass market without proper control and supervision by professionals. Re: House slab on H2 in 4 days 13Jun 19, 2020 11:01 am alexp79 Structural.Review alexp79 Correct me if I am wrong, but you can still use shallower footings even if movement is above 100 mm due to trees or extremely reactive soils, as long as the slab is stiffened enough? E.g. in Northern countries they often use 250-300 mm very well stiffened monolithic slabs (ie you virtually get slab-wide footing, stiffened with 2 layers of 12 mm bars forming 200x200 cells) on extremely reactive clays and they have freezing factor over there too! Why do you think builders won't be able to do controlled fill? It is not really that hard and I have done it for my house slab (following layered compaction technique and with radioactive compaction testing). 32 mpa concrete is for extra strength in this particular case, it may not be a specific Cupolex requirement per se, in fact slab on top of Cupolex can be even 60 mm slab with 25 mpa concrete. You can use monolithic slabs which needs significant more concrete and it is different then to waffle and Cupolex? this is beneficial when we are dealing with extreme movements, with existing trees I believe it is cheaper to do piers where required as you have settlement issues and not heave problem unless you are removing the tree. They will do control fill if you educate them and supervise them, ask Builders what is the difference between rolled and controlled fill, volume housing builders which do majority of work, do not have understanding of it and they never do it, they never found the edge beams of waffle slabs into controlled or natural soil, this is partially their fault and partially engineers who donot detail their slab design properly and leave it to builder to put a waffle slab edge beams on rolled fill, you just need to check some of the new build houses in Melbourne to see houses less than 3 month old with cracks. In an industry where we can't design and build a simple residential slab properly (volume housing mainly) from Australian Standards, I wouldn't suggest introducing more complex systems, you are technically competent but majority of home owners are not. My point re monolithic slabs is that if Cupolex engineers claim that they can achieve similar stiffness and with their system, then it should be more or less inter-replaceable? Although mono slabs require more concrete and reo (btw, reo costs can be significantly lower than conventional slab if Helix Steel steel fibers are used), they also require significantly less ground works (excavation of beams/extra set outs) and form work set up efforts when comparing to conventional rafted slabs, plus you can also sum up concrete and ground works required for excavation of the piers too in order to run a proper side by side costs/effort comparison. In the end of the day, considering the cost of labour, you might end up with not so significant difference when comparing to conventional rafted slab on piers. 20 extra cubes of concrete cost only $4-$5K which is what you roughly pay for 2 extra days of excavation and form work laborers, plus piers will add up even more. Let's also keep in mind that waffle pods are not really recommended for highly reactive soils. I am not totally against piers as long as they are properly inter-connected to the underlying slab to prevent soil getting under the piers when slab lifts off due to soil movement or at least protective flexible caps are used. I don't think a lot of builders/engineers following that. But yes, I completely agree with your point that we just can't really push new technologies to mass market without proper control and supervision by professionals. I understand and agree that they can be inter-replaceable, this is also similar to modifying a waffle slab if the engineer is competent enough. Generally by increasing the height you will get 3 times more stiffness than increasing the width (check 4.6 AS 2870 -2011), based on this, most of the time you will end up increasing the slab depth rather than modifying the width of beams or spacing, with waffle slabs you can achieve this by stacking up the pods or deepening the beams in stiffened raft slabs, will this be achievable with Cupolex given the maximum height is 350? Some engineers will not connect the pier into slab as they have used piers for bearing/settlement and designed (hopefully) the slab to take swelling pressure, also calculating the uplift pressure and designing the reinforcements and connection between the pier and slab edge beam is not an easy computation. Re: House slab on H2 in 4 days 14Jun 19, 2020 11:53 am Yes, Cupolex can also stack up, plus they manufacture domes up to 70 cm in height. Also, noone restricts from digging deeper edge beams too into the ground too. They also have Cupolex Rialto system (plastic pipes filled with concrete placed under the domes) which is specifically designed to replace up to 2 m of engineered fill! How can slab can take the swelling pressure if it floating? Will the swelling pressure lift the slab off the piers? 8 6156 I'll be here once a week, lets make that Mondays. If you have a question, this will be the day I will log in for a look around.. If your lucky, sooner. Ask away...… 0 6368 13 6632 |