Browse Forums Outdoor Living 1 Apr 23, 2012 3:55 pm HEY all, i am planning to build a deck in my back yard, however my backyard is all concreted and the land is slightly slanted. im planning to make a concrete box on in with rebar reinforcing the two concrete together.. i've attached a picture..and just wondering would this be strong enough... and advice and feedback would be much appreciated http://imageshack.us/f/69/deckt.jpg/ cheers Re: HELP WITH concrete foundation for post 2Apr 23, 2012 5:49 pm Looks good to me. I would probably make them about250mm x 250mm and put a bit of rebar or light mesh in the block. 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: HELP WITH concrete foundation for post 3Apr 23, 2012 6:19 pm Only problem I can see is water can get between the existing conc and the new blocks, rebar would rust out in no time. How many of these do you need? If not too many maybe you could cut about a 250x250 hole in the conc and drop a galvinized stirrup in. Re: HELP WITH concrete foundation for post 4Apr 23, 2012 7:31 pm mgilla Only problem I can see is water can get between the existing conc and the new blocks, rebar would rust out in no time. Should'nt be a problem due to slope, minimal joint due to being cast on existing concrete, and concrete being alkaline which resists corrosion. If you are really worried just use galvanised bolts rather than rebar. 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: HELP WITH concrete foundation for post 5Apr 26, 2012 10:08 am HEY all, Thanks for the reply...hmmm the rusting of the rebar...i might have to look into it more.. I'll probably have around 8-10 of these block.. any recommended height?!?!? i was thinking minimum height of two brick 15-20cm? of cos at the lower end will be pretty high due to the slope. thanks again Re: HELP WITH concrete foundation for post 6Apr 26, 2012 11:15 am Hi Quocxn, use 4 off 12mm rear per block and get them galvanized; that won't cost much otherwise they will rust. Make the blocks 300x300, put the rebar in each corner so there is 50mm concrete cover to each side. Cut them so they go the full height of each block minus 50mm. Roughen the surface of the existing concrete with a comb hammer or cold chisel to allow the new concrete to key to the old. Drill and epoxy the rebar into the existing concrete. On the taller blocks you may have to wrap fencing wire around the top of each bar to hold them in place. Use 32Mpa strength concrete. You should be good unto a 1m height. The other option, if there is enough room, is to bolt galv stirrups to the existing concrete (if if is in good condition and a large slab, not small segments) using galv dynabolts and use timber posts up to the bearers of the deck. The aim is to hold down the deck against an uplift wind. Normally the supports would be concreted into the ground to do this and the existing slab is reinforced and large enough its weight will achieve the same result. 2 Re: HELP WITH concrete foundation for post 7Apr 26, 2012 1:03 pm THANKS mike8136 i would prefer to bolt galv stirrups to the existing concrete, as they're all big slabs and in good condition.. its just that they're are not fully leveled.... so you rekon the best option is for the concrete box? i wan to make sure that it will last...it would be a pain if it wont... thanks again Re: HELP WITH concrete foundation for post 8Apr 26, 2012 4:31 pm The bonus of having timber posts that go up to your bearers is you can easelly cut them the right height for your bearers to sit on. It you bolt stirrups to the existing concrete just use gal washers under to get them level. I personaly would even get steel post made before i'd do the concrete boxes. It will take you ages and the cost of concrete and rebar would be heaps more than getting a post custom made. Re: HELP WITH concrete foundation for post 9Apr 26, 2012 6:23 pm Man this forum is awesome..im learning heaps! thanks mgilla for ya suggestion...its just that the concrete ground is not level which really restricted what i can do...i did think of steel post...however im not sure how i can implement into the slanted ground. so far i can only think on the concrete box! any other suggestion are welcomed...i wanna have all the options in the world before i starts spending $$$ Re: HELP WITH concrete foundation for post 10Apr 26, 2012 7:29 pm Mgilla is right with the timber or steel posts, flat bases (or stirrups) packed up with gal washers. Fill the gap underneath with non-shrink grout available from Bunnings and they will last a lifetime. Unless your concrete slab is at 45 degree angle this will be structurally sound. It seems very clear to me that your contract states that a security account does NOT need to be established so the answer to the builder is NO. If in doubt find a contract… 1 6361 2 28562 |