Building the new workshop ... may have light at the end of the tunnel!

[LizBurg]

Hi everybody, OK, I admit I've been lurking quite a while, well, almost forever actually, whilst building myself a new workshop but since I may be seeing light at the end of the tunnel now I thought it time to put up a bit about it. Lot of catching up to do, this will probably take several posts.

To start at the beginning ...

Once upon a time, there was a pleasant little garden behind the house and all was light and happy with Pimms in the summer sitting in the sun on a smallish lawn but then gradually darkness started spreading over the land ...

... as it got increasingly hidden from the light by the ever growing branches of the neighbours (4) Leylandii ...! In a garden maybe 30-35' wide, lower branches around 18' long were covering over half the (combined) garden. Looking out the back was a bit depressing to say the least as you can see from the photo, and that's taken from an upstairs window!. And of course a tree spreading over 30' at the base tends to be tall as well, in this case I estimated maybe 40' or more.

Fortunately, I love my little chainsaw (and its four larger siblings) so a deal was struck that the neighbour would let me cut them down for him for no charge (We can discuss another time if that was a good deal ...!) So, time to dig out the old climbing harness, get a few slings and a suitably hefty billhook and to start tunnelling my way up the inside of the trees, laying waste to all the horrible dead twiggery in the heart of Leylandii and clearing the trunk end of the limbs, gradually working my way upwards.

It really is interesting just how big the tree limbs you can cut through with a bit of nouse and a small 26cc 10" top handle chainsaw are. Not only that but make the wedge cuts right and you can drop them wherever you want. Remembering as you drop the lower limbs to leave enough protruding from the trunk to serve as climbing footholds is also a good idea - ask me how I know! Of course, trees being trees the branches hadn't confined themselves to spreading just one way so discussions were needed with other neighbours to allow access into their gardens to take down the limbs overhanging their land and in one case to climb up on the roof of their 'shed' to take down branches that were overhanging it as well! And all had to be done with out damage to anyone's property. Well, apart from the Leylandii of course, I could do as much damage as I wanted to them, and boy, did they deserve what they were getting. Delimbing with the small top handle saw had to be followed with breaking out the bigger ones. Sometimes it seems 10" just isn't enough ...

OK, takes a while, but the scars on my forearms from climbing up through the dead heart of the Leylandii all healed pretty well and even fairly quickly and to be honest it's quite good fun dropping first all the tree limbs then taking down the main trunk in pieces that will fit into the small garden area available to drop them into.

But .... the scars on my soul from then having to deal with the trees once cut up and lying on the ground run much deeper. It is amazing, or at least it was to me at the time, just how much bigger a tree in many pieces on the ground looks than one standing straight up. Of course the obvious way to deal with the detritus is to hire a big wood chipper, and truck then bish, bash, bosh, everything sorted in a couple of days. Well, that would be the obvious thing to do unless of course the only access to the back garden from the street is through a tunnel between the middle two houses of a 4 house terrace. A tunnel less than 5' wide and even narrower if you make allowance, as you probably should if planning to drag large tree parts through it, for the gas meter and supply which is on the side wall. Did I forget to mention that bit? (Bear that in mind, it will reappear in the story later)

That meant everything had to be dealt with in situ, or at least by being cut into small enough bits to be bagged up and carried out. Bucking the tree limbs on the ground was straightfoward enough, as was cutting them into pieces small enough to be easily lifted and a lot went into creating a mega sized woodpile. Just in time for my local council to ban new woodburning stoves without planning permission. Ho hum ...so it looks like I'm set for Guy Fawkes night for the next half century or so. Meantime, all the rest of the branches, maybe 1" diameter or less got turned into bits with a (borrowed small) garden shredder, bagged up and generously given, out of the goodness of my heart naturally, to a number of friends as an 'all natural organic weed suppressing mulch'. Well, be fair, what else can be done with a pile of shredded Leylandii bits 12' long, 4' deep and about 4' high? Answers please, on a postcard (to any address except mine ...)

Eventually though the day dawned when I made the, by then surprising, discovery of actual, solid ground beneath the endless tree bits, oh frabjous day, oh kaloo, kalay! (Woodpile at the far end, it's about 6' deep!)

Time then to start digging out for the foundations. Now this is where it all gets a bit complicated as the plan was, well still is, for a multifunctional workshop where I could work on my motorcycles as required as well as have a decent metal working shop the rest of the time. And all in less than 15 m^2 and less than 2.5m high of course, which means going down into the ground a bit as well as up. But this post is already long enough so if anyone is still reading, until next time ...

(Now, bearing in mind this is my first time posting, feel free to let me know if I should do some things differently, e.g. are the pictures too large, am I being too verbose, or is this all as boring as all my colleagues at work find it now after living with it on a day by day basis for far too long!) Thanks., hope this posts as I want it to.

 

[Jake]

That must have been an awful job so hat off to you. Our predecessors put in an overgrown hedge of that stuff and although small by comparison that was a horrible job to take out, that sticky smelly scratchy 'dust' is really unpleasant.

Look forward to seeing the more enjoyable bits!

 

[flying haggis]

Keep up the progress reports as we all love a good workshop build story here.

 

[Sachakins]

Welll done

 

[LizBurg]

OK, so last post I had finally arrived back at ground level, but why stop there? Forgive me for expanding a bit on the thinking at this stage as I hope it will make the rest of the build log look more rational. I'm not suggesting this is right for everyone, but it will I hope show what I considered in the build.

The basic idea of the workshop is to both serve as a predominantly metalworking shop to build small and model engines in due course, but as I said last time to be able to work on my motorbikes as well - in comfort! I hope to be spending a lot of time in the shop after I stop working and retire properly so I'd like it to be a pleasant place to be, and easy to keep clean. Also because I recognise that if it is literally a pain in the back getting down to work, then it just gets put off. So workbenches at a decent height and if I can lift a bike on a stand to a comfortable working height not only is work easier but I'll be much more likely to get on with things. Now the obvious thing is some sort of motorcycle lift but here the size constraints of the workshop come into play. Basically there are two types of lift, a parallelogram where the top plate not only goes up but also moves along in the long direction when raised or a scissor lift which just goes straight up and down. Now the first type are cheap and cheerful but need a longer space then the length of the working surface. Which in a workshop of the length of this one, allowing for enough space to put a milling machine at the end of the workshop and being able to walk round between it and a motorbike on the lift, is not feasible. So a scissor lift it has to be.

But then the issue is where to put it when it's not in use? Again there just won't be enough space to store it inside the workshop. All of which is the long way round to the conclusion the only place it can go is in the floor.

That means in turn taking the entire floor down about 16" to have a 4" base with 12" for the lift and the actual workshop floor back at ground level. Which then leads to the next issue of whether a simple wooden floor would be strong enough and sufficiently vibration free for mounting a fair size lathe and milling machine, weighing about 400kg each and in the milling machine's case on a fairly small base, about 30" (750mm) by 18" (450mm) (apologies to those who like metric, I'm afraid I am old enough to think in imperial when building although often then measure in metric and hope mostly to be working in metric in the shop. And if that confuses you, well, me too!)

Now whether it was a good idea or not, I decided that I should go for a good deep concrete base for all the heavy tooling and have the lift in a well in the floor so that in due course when lowered the floor level will be flush. Think of it as in essence a 16" thick concrete slab with a 12" deep rectangular well in it.. But of course that depth and size of concrete means reinforcement to stop cracking with lengthwise bending or verticallly, well so be it. The aim is to build once and have something that will see me out without major rework. A couple of layers of rebar mesh should be enough for that, suitably spaced apart and worst case, if the next owner doesn't want a workshop they can have a great home office, gym, whatever.

The next question then is insulating the base. Now expanded polystyrene gives good insulation and can take a (to me) surprisingly large compressive load evenly distributed, so that's OK. Last question, what about damp penetration, well, polythene DPM sheet covers that, laid in a bathtub fashion. So, with that in mind, time to start digging ...

First thing is to roughly mark out.

Last time I recounted taking out the large leylandii, but even before then I had had to take out an overgrown old elder tree which, whilst it may have been doing a grand job keeping the devil away was forever covering everything in dark black sticky berry droppings every year. Of course, cutting a tree down is only part of the job so after burning away as much of the stump as possible, next the roots had to come out (in the above picture from the far corner where the spade is... the next picture shows one of the roots still in situ at bottom right, but that was by no means the only one)

If you look at the far end of the area we have begun to dig you can see the marking out poles for the excavation. That root by the way went all the way to the right at that thickness. getting it out meant digging it free of the earth all round in various places then using the chain saw to dismember it. Hard to believe those roots ran under the old shed that used to sit there, guess that's why the floor wasn't so level any more! Nor the walls vertical. Come to think of it, the roof wasn't great either, ho hum.

Well, digging is digging and about the only points worth remembering are that (i) you have to have sometwhere to put the spoil (ii) a way to get the spoil out of the hole and (iii) a way to know when you have gone deep enough and can stop digging! So, stakes in the corners, levelled with string lines, and when digging leave a ramp to get the wheelbarrow up until last. Easy peasy. well maybe not physically but you get the idea..

Finally digging done it's then a question of getting the base roughly level, string lines, a laser and a stick marked at a suitable length for depth measurement did that job

A good few inches of MOT Type 1 ballast gets whacked down level to be followed with a couple of inches of sand

To be followed by the expanded polystyrene insulation, suitably cut to fit. Of course this stuff does like to fly away if there is any wind and all sorts of wildlife seem to like nothing better than starting to dig through it before giving up half an inch down, so weights and covers are the watchwords. Also, this sets the size for the formworks needed, the odd areas are repairs after wildlife as above

Then the DPM goes over the whole lot

Followed by a couple of layers of steel mesh, suitably spaced off the bottom with castles and with wire spacers to keep both the right distance between the layers and the layers 2" from the edges and surfaces, top and bottom, of the concrete to come. Where the deep concrete 'walls' are thinner normal rebars are tied in to provide suitable tensile bracing all round . Everything gets wired together at 300mm intervals.

Finally inner formwork for the well gets placed and braced as far as possible, though in retrospect more bracing should have been used. The well forms though will not be coming out after concrete goes in so they can provide suitable wooden faces to fit joists across the well for the flooring, the well being much larger than the lift will require. So now ready for concrete.

At which point after a quick back of the envelope calculation about how many wheelbarrows full of of concrete would be needed to be barrowed through the alleyway to the back to fill about 5 cubic metres sanity broke out and together with ordering the concrete a ground line pump was ordered as well. Definitely worth it!

But that's for next time

 

[flying haggis]

before you get to far ahead and start pouring concrete think about if you want any ducting into the building itself or across the floor into the pit for power/air etc

 

[Sachakins]

5 cubic metres, wow, I'd put a lot more gravel/ballast in there first,far cheaper per cube than concrete...

 

[LizBurg]

Thanks for the comments guys.

I have some ducting set to take a hydraulic line into the pit, will hopefully show it next week, but tbh found it easier to use a diamond blade in the angle grinder to cut the concrete after pouring, then use an SDS on hammer to remove the channel in between rather than get too fancy with ducting pre-pour. Of course, all I have to do wrt the lines into the pit are to channel them in the flooring concrete into one corner through the wooden frame of the pit, after that they can run anywhere under the joists in the pit. Hopefully will be big enough! The hydraulic pump for a lift will be outside the pit, only the scissor mechanism itself in the pit. The less to go wrong in the depth of pit the better. Also, the planned floor will include self levelling over the concrete anyway so the channel around the duct will get filled in easily.

5 Cubic Metres, when I say it's a slab with a well in it, on two sides of the well, the 'wall' is only about maybe 12-18" or so, but the other two side 'walls' are a metre wide to give space for walls and solid concrete base for the heavy machinery. Do you need that thickness? No, not really, but the alternative would have been a much more complicated set of foundations of different height with much more complex formwork etc. Possible certainly, though probably by doing less digging rather than making up again with gravel I would think. And the 5 cubic metres included the stuff that the pump guy missed the foundations with and put on the wrong side of the formwork. Such is life. On a side note, I don't know how much concrete is in other areas, but looking at Selco prices, MOT type 1 is pretty pricey. I tend to use Selco for building stuff, the prices are generally pretty good and they will deliver for free with orders over £50. And frankly it doesn't take much to get to £50 these days.

 

[Jameshow]

What's the pit for? Will the concrete not flow up into the pit area?

You landing harrier jump jets! Heavy duty!!

 

[LizBurg]

The pit is for an in floor motorcycle lift, in floor simply because I don't have room to store a lift when it's not in use. Why do I need a lift? Firstly because I'm gettig too old to be up and down on the floor all the time fixing bits low down and some of the bikes are in bits for restoration (that sounds a bit fancy for a couple of MZs! Do MZs get 'restored' or just 'fixed'?). Secondly because my main ride is a 1100cc BMW, which weighs the best part of a quarter of a ton dry, and it's a lot easier lifting that to working height with a proper lift rather than trying to manhandle it up a ramp onto a stand. And if I want a quiet life I also have to be able to work on my partner's Honda Shadow cruiser, which is a hefty old thing as well. The bike that is, not my partner!

As for the concrete flowing up into the pit, no, it's not really too much of a problem, no different to when casting concrete steps. The relevant measurement is the 'slump factor', which is exactly what it sounds like. You fill a hollow cone with concrete then remove the cone, the slump is a measure of how much it slumps by in a set time. When ordering the concrete if you tell the supplier what you need they can arrange it to have the required slump (and advise on required grade). Getting it pumped in through a ground line pump complicates matters a bit as there are limits on how stiff the concrete can be given the pump but that's something to discuss with the supplier.

If you look closely at the bottom of the formwork for the pit you'll notice that there are bits of 2x2 nailed to the bottom of the formswhich is to set the level for first screeding/finishing with a piece of 2x4. The more problematic bit in terms of the concrete flowing would turn out to be getting the concrete to flow well enough to fill in the space under the cross braces in place to try to stop the bottom of the pit formwork bending in under the pressure of the concrete. But remember, although I tend to think concrete as so heavy, it's only about 2-2.5 times the density of water, so the pressure at any given depth is only about twice that of an equivalent depth of water. Between the stiffness of the concrete and the relatively low pressures involved, seepage under the formwork isn't much of a problem with a bit of care. More on the pour and problems next time ...

 

[Jameshow]

The pit is for an in floor motorcycle lift, in floor simply because I don't have room to store a lift when it's not in use. Why do I need a lift? Firstly because I'm gettig too old to be up and down on the floor all the time fixing bits low down and some of the bikes are in bits for restoration (that sounds a bit fancy for a couple of MZs! Do MZs get 'restored' or just 'fixed'?). Secondly because my main ride is a 1100cc BMW, which weighs the best part of a quarter of a ton dry, and it's a lot easier lifting that to working height with a proper lift rather than trying to manhandle it up a ramp onto a stand. And if I want a quiet life I also have to be able to work on my partner's Honda Shadow cruiser, which is a hefty old thing as well. The bike that is, not my partner!

As for the concrete flowing up into the pit, no, it's not really too much of a problem, no different to when casting concrete steps. The relevant measurement is the 'slump factor', which is exactly what it sounds like. You fill a hollow cone with concrete then remove the cone, the slump is a measure of how much it slumps by in a set time. When ordering the concrete if you tell the supplier what you need they can arrange it to have the required slump (and advise on required grade). Getting it pumped in through a ground line pump complicates matters a bit as there are limits on how stiff the concrete can be given the pump but that's something to discuss with the supplier.

If you look closely at the bottom of the formwork for the pit you'll notice that there are bits of 2x2 nailed to the bottom of the formswhich is to set the level for first screeding/finishing with a piece of 2x4. The more problematic bit in terms of the concrete flowing would turn out to be getting the concrete to flow well enough to fill in the space under the cross braces in place to try to stop the bottom of the pit formwork bending in under the pressure of the concrete. But remember, although I tend to think concrete as so heavy, it's only about 2-2.5 times the density of water, so the pressure at any given depth is only about twice that of an equivalent depth of water. Between the stiffness of the concrete and the relatively low pressures involved, seepage under the formwork isn't much of a problem with a bit of care. More on the pour and problems next time ...

That makes sense!!

 

[LizBurg]

So now we've reached time for some concrete.

Of course the obvious course of action is to get a mixer, sand, cement and aggregate and water and off you go. Now according to Selco's calculator, that would need about 1.2 tons of cement, 2.2 tons of sand, 4.5 tons of aggregate and about 650 litres of water. That struck me as a bit much to carry through to the back so concrete supplier it had to be. Now given that it takes about 20 builders wheelbarrows at 80% of capacity of concrete to make a cubic metre, that means we'd be looking at maybe 90-100 wheelbarrows worth to be barrowed from the kerb through to the back if I got readymix and wheelbarrows. Hmmm, not realistic given I'm doing this on my own with mu ch appreciated help from my partner as and when needed. Of course you can get friends in to help, have a wheelbarrow party that sort of thing, but I'm not sure I have enough friends to burn half a dozen or so that way and I know for certain I don't have enough wheelbarrows. So ground line pump it had to be, and given the quantity getting it on a mix on site basis seemed the bext way to go. OK, the pump is a bit expensive but practically it seemed the best option.

So everything ordered, grade of concrete agreed and then waiting for the big day, putting in more bracing for the forms t.o be on the safe side. Now at this point to be fair the concrete supplier was fine, the biggest issue being getting the truck in a spot where it didn't entirely block the entrance to the kind of cul de sac in which we live. Big truck ,small entrance, OK but something that has to be borne in mind when getting concrete delivered.

Well, the best laid plans of mice and men and all that. My plan was that the concrete could be pumped into the centre of the various bits and fill out from there minimising the strain on the formwork. Unfortunately, the pump (and operator) had other ideas and fired the concrete as high speed directly at the side of the forms which shifted them a bit, not awfully but annoyingly. Part of the problem was that a couple of times during the pour the concrete truck had to be moved so then the line slowed down and then restarted so pressure wasn't that constant. Put that down as a site issue, especially the lack of any off road place for the truck during the pour.

OTOH, we got the entire load in in about an hour and a half and boy, when they push the sponge ball through the pump line to clean it afterwards the speed it comes out is pretty darn impressive. Reached the far end of the garden, maybe around 30-40 feet or so, without touching the ground on the way..

Quite a bit of pushing wet concrete around and some spade work to move excess from one side of the forms to another, get everything roughly in place, and as you can see on the right a bit of excess got dumped outside the formwork, but more on that later. Got it all initially floated with a long 2x4 and thought it might be time to break for a cup of tea until it was ready for floating properly. Yeah, right, this stuff was curing fast, first time I checked it was already at the point of being ready for a final float so cracked on with that. A bit of a hectic morning really, but by just a bit later it had gone off enough to be covered with builders hessian, the hessian soaked and then covered with polythene to stop it drying before it could cure properly.

And then what we felt was a well earned drink seemed in order (you'll have to picture that for yourself, no photos!). Of course it then decided the next day to rain, and the day after that, and the day after that, and so on for about a week or more.

So it was regular visits to make sure things didn't get too bad, and of course getting the inevitable cracks at work about how was the new swimming pool coming along. But eventually we got the concrete uncovered and could start doing a bit of tidying up.

The demolition saw made short work of the stakes supporting the forms and the very thin concrete just flaked straight off the dpm plastic which left the end result apparent and ready for a bit of tidying up.

A couple of points, the grooves in the side of the slab left by creases in the dpm are in fact all very rounded , so rightly or wrongly I doubt they will be stress risers to start cracks, the very edge was easily smoothed off as required to get rid of any sharp points. Of course, what I should have done is used a radius float to round the edge when I did the floating of the concrete, my bad. Yes there is a bit of a bulge on the right where the door will be, but beyond that under the plastic it's not too bad.It will need a bit of levelling in places but could have been a lot worse.

The worst bit was where significan amounts of concrete had wound up outside the formwork in the ground channels. That had to be removed so that meant breaking it up with a SDS drill on hammer action. Key tip there btw, if the pick end (pointed chisel) you are using in the SDS drill is too blunt (because you've already used it to break up a huge piece of concrete left over in the back garden by the previous owners/builders) it takes forever. When that realisation finally dawned on me, I got a new one and the difference was absolutely chalk and cheese.

Heck, a little time later I was intermittently watching some builders pour concrete steps at a site next to where I was working that day when they gave a fine demonstration of just what can happen when the forms give way whilst pouring concrete! I managed to guess what had happened by the tone of voice in the shout of 'Stop, stop' even before I turned round to see!

Anyway,all in all, could have gone better, could have gone worse, nothing unfixable,. Given I'd never done anything like this before, not going to beat myself up too badly about it and as it turned out, one point where the formwork shifted created pretty much the channel I had planned to put in the concrete for the hydraulic line into the pit anyway. But that's for way down the line. Felt like a huge milestone had been reached. Finally, finally getting out of the ground and that's always a big step forward.

Time to start on the walls, next time.