What’s the correct way for the usual basic extension? String line off wall and then use this as the centre line? Or should it be offset one way more than the other?
That’s a good plan. So I could run the string off the outer edge of the wall then use the stick (at the wall edge mark) to spray a line down it for bucket edge or centre.I'll go either I normally go outside as preference though I normally make a stick with three marks on it 600 long and a mark for both sides of the wall and the center
seen a few like and worse than that put a steel frame up once .. fair size one...one end - the start was alright ... by the time we got to the other end the col.s were sat on piles of blocks 15" outside the footing/slab, on the one side ...... fk knows who set it out ... but they were specialists apparently
these were supposed to be on the slab .... had to trek to Bognor to sort these out .... bloody ground workersseen a few like and worse than that ..........
I am usually the digger driver and the Engineer! Just finished a large timber frame house foundation where the erectors said it was the best for level he has worked on and longest diagonal was 18mm long over 20m. Told him to get a new tape!!!I've done tons of foundations, some set by engineer, others I've had to do set off a hedgerow! (TiltyShaun will know my pain there especially as it was a timber frame) It doesn't matter how you do it as long as you are consistent with your method. Some tips I've learnt;
1. When doing extensions - existing houses are rarely square and if the new extension is a wrap around then this can really screw things up. Pick a side (usually the longest) and go with that, regardless if it makes it unsquare to something else.
2. If there's steel framework in the new extension, this is particularly important as you have to go with the wall thats squarest to the steel frame if that makes sense.
3. Never assume the architect has got his dimensions right - I've had to do plenty where we had to "make it fit" But always ring the architect to tell him how stupid he is so he can adjust the drawings for steelwork people etc that come behind you.
4. Builders are rough bastards and providing you dig somewhere roughly where it looks like it should be, they will be impressed that you even turned up - let alone got it in the right place. I believe the saying is "it looks alright from my house"
totally agree ..... with the target/sensor on a batten it'd be a doddle to check every 6" if you wanted to, from a standing position. ... level some pegs first for a datum, 'praps, but then there'd be no need to find 'em after ... just listen for the tones as you work a way aroundlasers have made foundation work so much easier these days.
laser the concrete into the footings and the brickies will love you. Pythagoras everything even after marking out with the squaring laser. I use leftover bags of plaster to mark the lines on the ground as im too tight to buy spray paint.
Couple years ago now watched them put up a timber frame on the site opposite and they used plastiv packers under the frame to get the whole thing level! They used spirit levels and pegs when putting in the conc. 10x harder and slower than screwing the laser receiver to a piece of batton and putting in the conc bang on, rake and tamp as you go. bollox to all the bending down an dipping a level on top of wet conc.