Browse Forums Paving & Concreting 1 Oct 17, 2010 11:22 am Hi there, Here's a case study for a lazy Sunday How would you design a pergola/alfresco slab at the back of the house, along the back external wall of the house? With the design, I mean actual engineering-like planning, taking care where to place components of the slab such as piers, other footings, MB, reo, etc - if you would use any of those. Facts: - The land is sloping to the back (away from the house) - The area is in the fill section - The height of the fill is approx. 500-600mm from NGL at the furthest point away from the house - The fill has not been compacted (it's rolled fill) - The soil is heavy clay - Approx dimensions: 8m long (along the house walls) x 4.5m deep (into the backyard) - There are no trees nearby The purpose of the slab: To provide floor for a future pergola/alfresco structure. Complications: There will be a retaining wall at the end of the slab. The wall will be separated from the slab by a garden bed, approx 800mm wide. I know by now you've all become very familiar with our backyard dilemmas, so I guess attaching THAT sketch again is no longer necessary ... I think it's been permanently embedded into everyone's brains My signature is distracting people from my wise posts ... Re: Slabs - Calling all engineering & experienced minds ... 2Oct 17, 2010 11:31 pm ouch my head hurts just reading that lol Follow Feggle viewtopic.php?f=31&t=34992 Follow lilfeggle viewtopic.php?f=31&t=37149 Asbestosis Sux! Don't breath in Asbestos Re: Slabs - Calling all engineering & technical minds ... 3Oct 18, 2010 7:19 am Oh, but why!?! ... after all, this thread is aimed at the technically minded OK, fair enough, might be too hard for this forum ... with no engineers around My signature is distracting people from my wise posts ... Re: Slabs - Calling all engineering & experienced minds ... 4Oct 18, 2010 10:23 am The way to design a slab is to work from the top down. Need to look at the roofing material, then the load transfer points then look at the slab together with the soil type. Re: Slabs - Calling all engineering & experienced minds ... 5Oct 18, 2010 7:48 pm B STAR The way to design a slab is to work from the top down. Need to look at the roofing material, then the load transfer points then look at the slab together with the soil type. Thanks BS. OK, so the roofing type is missing in my "specs". It will be something like Laserlite. The pergola will be timber. Don't know exactly what do you mean by "load transfer points" - location of pergola posts perhaps? Also, what do you mean by "look at the slab together with the soil type" (which is clay)? My signature is distracting people from my wise posts ... Re: Slabs - Calling all engineering & experienced minds ... 6Oct 18, 2010 9:47 pm shouldn't the council have all the engineering specs for this stuff?? i've put a pavillion 9mtrs long against our pool, stand alone, i drew it up and submitted it - and the engineer just changed my footing sizes ( although in perth we're playing in sand) Follow Feggle viewtopic.php?f=31&t=34992 Follow lilfeggle viewtopic.php?f=31&t=37149 Asbestosis Sux! Don't breath in Asbestos Re: Slabs - Calling all engineering & experienced minds ... 7Oct 19, 2010 6:26 am Yep ... although the people we are seeing are saying that this does not have to go thru council - but that's another story and I'm working on it. Another trouble is, we can't get a price if we don't know what do we need and how much of it. The guys just want to pour a thin slab - all on uncompacted and sloping land When asked, all of them would put piers, but only as deep as the fill, or shallower. But the biggest trouble is - why go into all that trouble if you don't even know if you are getting a proper solution. I think that we actually need something like deepened edge beam slab - anything less is not going to hold all that fill for too long, or properly. I think that the extra little garden bed is also complicating things furhter ... depending on the solution. My signature is distracting people from my wise posts ... Re: Slabs - Calling all engineering & experienced minds ... 8Oct 19, 2010 6:31 am lilfeggle shouldn't the council have all the engineering specs for this stuff?? i've put a pavillion 9mtrs long against our pool, stand alone, i drew it up and submitted it - and the engineer just changed my footing sizes ( although in perth we're playing in sand) When you say you "drew it up" - was it just a sketch drawing, or a proper engineering drawing? Did you specify exactly where each piece of reo goes, etc.? So Councils have this stuff 'ready to go'?! Hmmmm ... could save me some $ on structural engineers ... My signature is distracting people from my wise posts ... Re: Slabs - Calling all engineering & experienced minds ... 9Oct 19, 2010 6:57 am It is pretty simple really. Where you are coming from is where you are going to... Re: Slabs - Calling all engineering & experienced minds ... 10Oct 19, 2010 9:41 am Yep, pretty much, i drew it to scale, specifiying what materials i was going to use (which are available off the council websites) footings for the pool are worked out on a scale/diaganal thingy - we had to go rather deep at the deep end and not so deep at the shallow end (this was explained by the building dept at the coucil) all i had to do was make sure i followed the instructions. Once footings in and posts up - we had poured limestone as a base - simple! http://i896.photobucket.com/albums/ac166/lilfeggle/106094305il1256270222.jpg http://i896.photobucket.com/albums/ac166/lilfeggle/106094305ml1256270217.jpg Follow Feggle viewtopic.php?f=31&t=34992 Follow lilfeggle viewtopic.php?f=31&t=37149 Asbestosis Sux! Don't breath in Asbestos Re: Slabs - Calling all engineering & experienced minds ... 11Oct 19, 2010 6:03 pm Lovely blue colour!! And you're right re. Council. I did find some ready to use general eng specs for various things, but not patio slabs. So, if anyone knows that their council has them, can you please let me know. And what do you mean "simple"?! Don't you know that nothing is simple!!! My signature is distracting people from my wise posts ... Re: Slabs - Calling all engineering & experienced minds ... 12Oct 19, 2010 8:18 pm hehe depends on how you look at it - i'm sure a 60-90mm slab thickness doesn't google give you an answer lol Follow Feggle viewtopic.php?f=31&t=34992 Follow lilfeggle viewtopic.php?f=31&t=37149 Asbestosis Sux! Don't breath in Asbestos Re: Slabs - Calling all engineering & experienced minds ... 13Oct 19, 2010 9:05 pm Depends on how 'soft' the fill is. You could get away with having 200mm wide edge beams with 2 or 3 x 12mm bars at the base. Use SL72 mesh with 35mm cover for the slab. 100mm slab will be plenty. Now if you’re bearing columns on the slab you should deepen/strengthen that area. Now get the shovel out and get digging EDIT: use 25MPa concrete. The above would be over designed, but will do the job Re: Slabs - Calling all engineering & experienced minds ... 15Feb 14, 2011 11:01 pm lilfeggle Yep, pretty much, i drew it to scale, specifiying what materials i was going to use (which are available off the council websites) lilfeggle, could you send me the link for your council? Ours doesn't have this stuff, they concentrate on protecting and maintaining their own infrastructure, not on private structures. And definitely no slabs, or patio slabs, or pergola footings on patio slabs on sloping ground!! footings for the pool are worked out on a scale/diaganal thingy - we had to go rather deep at the deep end and not so deep at the shallow end (this was explained by the building dept at the coucil) all i had to do was make sure i followed the instructions. So this is for the pool, but what about pergola? Do you have any actual eng. drawings for post footings? I imagine them being some kind of pad footings at least 300mm wide by XXX deep (depending on the sand) ... ?? Once footings in and posts up - we had poured limestone as a base - simple! I also imagine that all you had to do is to formwork the area and pour the slab - all being level ... so no need to deepen some edges or do some piers?? My signature is distracting people from my wise posts ... my suspicion - some builders, they do usually make 'odd' settings in their site plan / pricing as their standards - being hopeful that first - the initial price is… 9 2486 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 31831 Thanks for all replies. I just noticed now the pictures I added to post right on top of page were wrong. I attached pictures showing "current" and my "suggested" floor… 9 14644 |