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A retaining wall probably isn't entirely necessary, as the worst that would happen is it collapses down against the workshop wall. However that would eventually lead to damp.
If you put in a retaining wall, it stops moisture being held against the wall, and should stop moisture soaking through the wall.
We got a builder in to do the conservatory but I did do quite a bit of the work myself. The concrete pour wasnt really difficult. Started at the middle and worked out from there. The hard part was walking about in the concrete while pouring it and trying not to fall in it!
How close are you building to your boundary? Can you build the retaining wall at the boundary and leave say enough space to lay a row of 450mm slabs around the workshop for maintenance access?
about 600mm from the boundary at the back, 900mm to the LH side. My problem is that adding a retaining wall adds another 300mm to the dimensions and already SWMBO isn't too happy. I think I'll see if i can take it back further, but I cant go any further left because of a laurel bush that I want to retain. If I can level it more on the left and leave just the need for a rear wall and grade the RH side a bit that should be OK. Else I'm looking at £700 of sleepers to make a wall, but at least that won't need a concrete foundation, just some post-crete'd holes. A poured concrete wall is another option at only .7cu m of concrete (100mm wide at top, 300 at bottom, 4.1 m long, 800mm high) but needs some complex form work and wouldn't look so nice.
A concrete wall will look fine with a bit of roughcast on it and some flag stones on top. Seeing as your getting the concrete anyway you need the foundation and shuttering.
Well end of day 1 and not entirely to plan. Digger didnt turn up til gone 10 but I'd spent the first couple of hours chopping up a crazy paving path that cuts across the corner of the dig. With a cold chisel, a 5lb club hammer and the bosch power chisel... hard work... if I'd known how difficult I'd have hired a kangol but i would have only needed it for an hour or so... then the Muck Truck (powered wheelbarrow) got stuck in the garage back door.. the gap was 705mm the muck truck was supposedly 680mm... yes apart from the hubcaps which needed another 30mm, so had to take the door off...
Anyway, dug out about 1/4 of the area at the deepest end, down to 730mm or so... will finshing digging the rest before doing the final 100mm just in case my land surveying is a bit off...
will put up some pics later when I've eaten and dragged them off the camera... but here's the boys toys taken on my phone...
Attachment 6797
Day 2. Digging continues... couldn't start making noise til 9:30 cos SWMBO said it wasn't neighbourly, so was out to Wickes at 7:30 to get a 1800mm spirit level, a folding builders square, and a six pack of 2 x 2 to make stakes from. Had my youngest son helping today driving the barrow so that made it faster, tho the amount of damage to the garage back door frame does make me question that... I was planning to replace that door with a uPVC one sometime as the door itself is going rotten - so might be sooner than later, well have to order doors/windows for the workshop so whats one more door lol (about £250 or so in case you were wondering). Masses of tree roots made digging slower than hoped, each one having to be chopped several times, the digger isn't man enough to lift a 3" dia root and there were about 2 dozen of them under the surface (and still more where I've not yet dug I'll venture). Really needed a chain saw, the circular saw can't handle living wood well, so really only had the mattock/ax and that makes it hard work...
I'm hoping tomorrow will see the end of the digging out, leaving Monday for levelling and tidy up of the sides... at least the digger is in the hole now, was a scary job driving it down the short ramp of earth. Apparently I should leave a ramp in then dig the ramp out after, but that makes it harder, esp as the only place to put the digger will be in a bush I want to keep. I'm thinking 6 pieces of 4 x 3 on end to make 4 x 9, 2.4m long with some 2 x 2 spacers will make a couple of ramps @ 12% (is 4 x 9 overkill for .9ton?) and they can be reused for the shuttering or the out of sight framework for the benches.
Decided to go for a concrete retaining wall, with some extra mesh in it and a DPC between it and the earth, and I'll bury a land drain pipe behind the dpc.
Now, how do you fix a concrete fence post? managed to catch one with the digger when I got confused with my levers :( and it cracked about 6" up from the base... I guess I need to get a new one but how do I get the old one out?? I'm wondering if the digger will lift it out with its cement block... assuming it was post-creted...
Well, just an update... today sees the completion..... of the hole...
Even with the digger and the powered barrow, this was a task I seriously underestimated.
Firstly, 1 foot or so down and we hit London Clay... initially that was easy to dig, like spreading butter, but once exposed to the sun it turned into concrete. Even harder were the deep patches of water-worn stones embedded in the clay. Sadly no fossils though I did break open some likely looking nodules of flint.
Then it rained, albeit briefly, on Wednesday night. By Thursday morning my hole wasn't looking like a swimming pool as I feared but the clay had gone all gloopy and walking on it meant you sank in about 2". It was unworkable for a couple of hours til it dried in the sun and then it was unbreakable :(. But I persevered. Damp clay is incredibly heavy so I found I could only half load the barrow else I couldn't manouver it. So now I have pile #2 in the drive (pile #1 was removed by grab truck on Monday) - something like 17 tons of earth has been shifted, all on my own.
Attachment 6865Attachment 6866
All the wood for the shuttering is now sitting on bricks under a tarpalin, so will assemble that this weekend in sections and do a trial fit. Then have to order the reinforcing mesh and the ballast and sand. No powered barrow this time so willl have to manually shift it all, but theres a lot less of it... biggest problem now is finding the time.
Here's the design of the retaining wall to go across the back.
Attachment 6867
Well the hole is done...
A second grab truck (same firm) removed pile #2 today. Both piles have gone to be landfill to sculpt a new golf course in South Mimms. (not a bad business this grab trucking... you get paid to take it away and paid to deliver it on the same day lol)
Attachment 6877
This is before I cleaned it up and tidied the edges... its 6.34m x 4.14m and 275mm deep in the nearest corner, 800mm deep at the far lh end. The bottom is flat to within 3cm which I reckon is good enough.
loks awesome, can't wait to see it all done and your machines in there.. keep up the good work
Irving, its amazing how fast you work, from drawings to actually getting started. I suppose when there's something on your mind and you're thinking about it all day, things get done. Keeps the pics coming, its a very interesting thread.
I'm surprised your other half hasn't told you to keep digging and make a swimming pool instead, lol forget the shed and concentrate on relaxing.
Well I'm still not 100% sure how to do the next step. I understand the general principles but the detail still needs hammering out. But the winter approaches rapidly and so I thought I'd make a start on the hardest bit... before SWMBO realised exactly how big it was going to be :). I have to say I am quite proud of my hole.. but I need to get on and fill it. Problem is I can't be home to accept deliveries, I need to be at work (I sort of managed to scrounge some extra days last week by agreeing to be on call over Xmas, but I am now all out of holiday till next Jan) and most places don't deliver Saturdays. So I can work from home some days but the logistics are complex! And I really only have weekends to work - those that are not already allocated to family stuff. So next weekend I hope to finish the shuttering (didn't get any movement on this this weekend as I'd hoped) and, by then, have ordered the ballast, sand, DPM, reinforcing mesh and insulation. I don't have room in the garage to work on the shuttering, it has to be done outside on the patio :(Quote:
Originally Posted by Iwant1
So the following weekend will be preperation work and hopefully I can get a concrete pour during the following week - 2 weeks out. Then I have to wait at least 14, pref 28, days before I can start on the walls, but that gives me time to order them and the roofing stuff. Once all thats in place I can work on the inside through November and do some evenings so it'll go faster. I'll leave the external cladding and tidying as long as possible... maybe into next spring lol.
Well best laid plans etc....
The hole is still there, though its now doing a very poor impression of a swimming pool filled with porridge.
I was rushed with the digger and hadn't realised it was 100mm narrower than I needed and a little wasp waisted. Fortunately being relatively soft due to the water content I've managed to tidy up the edges and now its sides are parallel, vertical and the correct distance apart and I have dug the post holes for the 4 x 3 posts that will hold the retaining wall at the back. That'll be made of 4.2m long 225 x 50 (9 x 2) boards.
In the meantime I have finally completed the design of the steelwork needed in the concrete. Why do I need steelwork, isn't that a bit overkill I hear you ask? Well maybe if you dont care about cracks appearing in a couple of years time, but I want this to last 20years and still be stable and because its on a clay base and near a tree it has to cope with heave and shrinkage. The normal solution to that is to dig deep piling into the clay, about 4 - 5m deep or more and suspend the raft on top. Thats not an option for me, so the alternate is to build a concrete raft thats sufficiently strong to stand the lifting forces and also support itself if the clay shrinks from underneath a section of it.
The research into how to design such a raft has been interesting, there's surprisingly little info. A civil engineering graduate son of a friend said that it wasnt something they covered in his Uni course. But I have persevered and have now a design that meets the demands of BS8110 and I am confident it'll handle pretty much anything. It does come at a cost of £400-odd of extra steel but that was 1/2 the cost of the extra concrete needed in an alternate approach (not forgetting the need to dig the hole deeper as well).
It does make me wonder just how good a job the companies that estimated this work for me would have done. Yes they might have finished now, but the life-expectancy of the work would have been severely compromised. One wasnt using any steel at all ("not needed") and the other said "oh we'll throw some in if you want".
Here's a Sketchup of the steelwork... all 418kg of it!
Attachment 7031
OK, so having stared at my swimming pool/hole for a few days, I tried to work in it this weekend... after an hour of struggling in the porridge I gave up. I now have some inkling of how the soldiers in the trenches felt about the mud! So i need to empty the water from the hole so it can at least have an attempt at drying out. I need a pump that can handle dirty water, can pump close to the base (a lot can pump down to 4", well its not much deeper than that in places) and can shift around 2500litres in a reasonable time... suggestions? or can anyone lend me one for a couple of weeks?
Would it help digging a small sump hole in the middle from which to pump?
Yes, I'd just about figured that idea out myself :) there is actually a sump at one end where i was a bit enthusiastic with the digger but there's a ridge to the other end so I'd have to dig (dredge? lol) a channel...Quote:
Originally Posted by WandrinAndy
I'll see if we got a spare pump at work Irving, can't promise we have one spare but you never know. It'll be though but I have a transformer you could borrow also. If you had asked last week I could have dropped one round as I was working in Hendon this weekend.
Thanks Peter... Mocha has also offered, but its the logistics that always defeat these things... so the more offers the better - let me know if you have one...
Oh btw , heres the paddling pool of porridge... :(
Attachment 7088
hmmm... not sure where to send the water... the nearest drain/sewer is about 10m or so towards the camera... it cant go left or back as thats uphill... and right means flooding the back of the neighbours garden.... so drain/sewer it is... so I'll need some 10m or so of 1.5" or 2" flat hose or whatever the pump takes...
You don't need 2" for that little amount, some 1/2" hose on a little hippo pump would clear that in 30 mins and easily keep up with any incoming. A 2" pump would drain that lot in probably 2 minutes.
Thanks Peter.... I just know that filling a paddling pool with a 1/2 hose takes forever lol :)....Quote:
Originally Posted by Peter.
Small hippo would empty that easily and pump it 10mts to the drain. My small hippo can take a 40mm id hose. Empties my 2000 gallon fish pond in around 1 hour.
Mocha's Hippo is doing well .. three hours (limiting factor was the 1/2 inch hose cobbled together with duct tape) and it looks like this:
Attachment 7108
need to move it to the back to shift the remainder...
If you are doing a lot of groundworks anyway you might to dump a load of tubing down there and do a ground source air pump.
Thanks. Interesting idea, but the additional depth I would need to dig, some of the regs and the need for planning permission make it a non-starter...Quote:
Originally Posted by D.C.