A question maily for Squizzy as I think he puts down house pads as as being from down under would know what is needed, but anyone else feel free. The question is what do you need to do? Sounds simple I know but I have not had anything to do with putting down a pad for a house and have now have a couple of people ask so figured I would look into it. I put down shed pads etc just not a pad for a house, anything different? and what kind of tolerance is needed for the finished level? cheers and thanks
We have done a few house pads here, xrlentau6, and a lot of shed pads and there really is not much difference. Where we would use a wet 20mm Quarry Rubble for a shed base, we use wet Crusher Fines for a house pad. The builders tell me the fines cuts out cleaner than coarser material, when cutting the wall tracks. Up around the Copper Triangle they used to use a red sand, because there was plenty of it and it was cheap, they probably still do. I presume you are talking pads for a concrete slab. The important thing is to use a material that when compacted, it will stand up when the foundations are cut into it, ready for the concrete. Most of the pads here, they require 150mm of compacted material and we try and finish it to +/- 10mm. We don't get real fussy about it because the builders chop it all up when they dig the foundations anyway. For campaction we use our wheel loader, other contractors use small vibrating rollers or their bobcats. One of the major house builders from Adelaide, is building a house over here at moment and their foundation preparation was the roughest I have ever seen. They spread a bit of 20mm scalps around and that was it. I guess different builders have different requirements, but that is how we do it here. Rn'R.
xrlentau: AS 3798 provides the guidlines for commercial & residential earthworks. AS 1298 is the standard for compaction. http://www.saiglobal.com/shop/script/details.asp?docn=AS0733780962AT In this country, the standard of the house pad is the builders responsibility. Basically you should never do a pad without a specification...which can usually be found in the instructions on the builders drawings. You will be surprised at how many people that do pads don't even know the basics of a the specifications. What follows is the long story short (insert disclaimer). The material shall be a) free of deliterious material (organic matter which can break down)....roots bigger than a pencil have to go. b) free of rubble/debris c) free of clay (specs in standard). The compaction required depends on the size and type of the building. A more rigorous standard may apply for two storey as opposed to single storey. The material used for fill is a local thing...you use whatever is accepted locally so long as it meets the above 3 requirements. Cracker dust, as RnR said is great product. Ask around. You need to find out who is doing the compaction test. If the builder wants you to organise it, find a local engineer who does the test and go see how its done. As her/him about the local conditions and the problems they have. Over here a Perth sand penetrometer does not test the first 150mm. We test the first 300 (from 150 to 450mm) for a seven blow pass on single storey construction. For retaining walls, multi storey and commercial we also test the second 300 (from 450 to 750mm) for a 9 blow pass. You need to know the depth of testing so you can acheive the correct prep. When we are doing the job we always dig some holes to double check the builders soil report. You are looking principally for clay or solid rock (or buried Volkswagons ). Should you find it, tell the builder, its his call. Don't make the decision yourself. In new developments 90% of the this work has been done for you by the developers earthworks, and you can have a deal of confidence that you are really just finishing the pad off.......but assumptions can be the mother of all stuff ups. I often find very poor compaction over sewer piping and behind large retaining walls built by the developers. Whilst on the topic of sewers its not a bad idea to check the drawings for the locations of the services and/or dial before you dig....especially on a cut and fill job. Again, its really a geographical thing. Up in them thar hills behind Perth we have done jobs where we had to put two pulls of Geo-grid into the pad. Compactors: You can't go past a 700kg plate compactor if you are going to be doing house pads on a regular basis. A 500kg platey is just too slow, although it is what most rental places have. I rented these when I started as they are bloody expensive to buy. A 2 tonne double drum vibe roller is the ducks guts but you have to be able to move it from site to site. After all that it comes down to experience. Some soils you can knock them to a level, give them a buzz with the compactor and pass every time.....other need to be brought up in lifts (150-200mm) and compacted between each llift. I have my own penetrometer which I test the site with before I start and then as I'm compacting so I know what the hell is going on. Always peg out a pad with at least 1.5m outside offset and work to acheive level and compacting 1m outside the building lines. When importing fill to bring the pad up to level always allow 15 to 25% extra fill for compaction. You will need: 1. some pegs and tape to indicate the level 2. laser level 3. the drawings 4. a machine of sorts 5. compactor 6. thermos & coffee I don't do house pads much anymore because we had guys running around here doing them for $400 and crap like that. The thing I did find helped me save time was one of these: http://www.earthmovinglasers.com.au/universal-laser-receiver-p-54.html As for the standard of level:beatsme I work to +-8mm on residential. Its up to the builder. I was once called to a 4000m2 site to "fix the loader drivers stuff ups". I walked around the site with the supervisor and he had paint marked the pad "+5mm" and "-5mm". Now that pad was as dry as a witches armpit....one pass backblading was probably going to change the level by 10mm. I thought the loader driver was a genius for getting it that close. The super was ranting and raving about how bad it was. He nearly had kittens when I asked for a water truck....so I duly sent my labourer out with the laser stave and I drove around that site for about 9 hours looking like I was doing something then handed them a bill for a G and went home still wondering . Every site will present different requirements....if you start with a sows ear you need to turn out a silk purse.
i do alot of house shed and tank pads around SA I work to +-8mm like Squizzy. Sheds and house foundations generally have piers down into the natural to eliminate subsidence but as mentioned always work to the engineers specs. Tank sites are another story they need to be completely on natural ground so there cannot be any subsidence and i generally spread and level the sand base to +_8mm then hand level it with a concrete screed to +- F/A cos the tank installers are so anal it sucks but i just factor theextra half an hour in to the job. The biggest prob is the cowboys doing these sort preps badly for $400 then we are expected to do the right thing for shte money. so my one advice would be dont try and compete tell the customer your price and why if he goes cheap it his prob. the last one i went to i got ditched for the cheaper guy by a long standing building contract, only to get a phone call a week later to go and finish the site. his idea of site prep was drop 2 tandem loads of 20mm rubble knock over the piles dont set the laser up load machine and leave. i laughed when i saw it. builder said it best "you get what you pay for" his job was put a week behind till i got there to fix it. so in short charge what you want but give value for money and you'll always be too busy
You must have different tank installers over there, johnboy. We have done quite a few pads here for large bladder tanks from all the major companies and haven't had any problems at all. Rn'R.
Thanks guys for your advice so far. Am thinking that I might leave the house pads alone at this stage, have seen how a few around here are doing them and pretty sure they are cutting corners so dont want to try and compete with them. Will kind of stick to what I am doing, the one area I am tying to get more work is the moving of fill. Mainly after they have dug the footings as have heard some are charging $15- $30 per tonne to take it away and it is after all clean fill. Have been working out my price's and am anywhere from $9 - $17 a tonne depending on where it is and this still works out atleast $100 per hour. Squizzy, that link for the laser reciever. I got one of those not long after I started and welded a pole onto a spreader bar. Have new spreader bar so have to weld a new pole on. But when working on my own the thing is great. Really big thanks for the dicussion here, is good to be able to find out what should be done to work out if thats a direction one might want to go down. Would not like to start doing something because it looks easy and get a bad name for doing a crap job. Cheers all.
If the fuel gauge dos'nt fluctuate too much when the machines turned around , that's close enough .