Whacker plate

[RikM]

I can't afford to lay down half a meter of concrete, so I am planning to compact the area and cover with weedstopper fabric and a couple of inches of limestone chippings. The obsy shed will sit on 10 double-height breeze blocks. It is a new build property, so the ground surface has only been down 18 months.

What size whacker/compactor do I need to hire? Will this baby one from Jewson be sufficient? http://www.jewson.co.uk/tool-hire/compaction/plate-compactors/products/2495/lightweight-plate-compactor-350mm/

[101nut]

To be honest, by the time you've done all you say, half a meter of concrete would probably be cheaper ...

AndyG

[RikM]

To concrete it (1.75m³) would be about £300. A bulk bag of 10mm crushed limestone, a roll of weedstop, and 20 breeze blocks (including delivery) cost £95

[Tinker1947]

Will the Obby be attached to the Blocks or have Timber supports in the ground....

[RikM]

Not sure yet. I was planning on driving in a few lengths of angle iron and screwing the wood base frame to those.

[Lonestar70]

Hi Rik,

 To concrete it (1.75m³)

 How do you arrive at this amount?

3metres x 2 metres x 0.1m = 0.6 cu metres... even allowing for a bit extra all round 0.75 cu metres should be more than enough.

Or are you including the pier base in this figure?

if this is so, and the pier base needs approx 1 cu metre... then the 0.75cu metres of extra concrete will cost much the same as the chippings and weedstop... but will be much more stable.

Interesting build.

Best regards.

Sandy.

[RikM]

Well I've got the stones laid and spent an hour going over it with the compactor but the ground is simply too wet to compact down. It's like custard with a crunchy topping. I chucked a few breeze blocks and the Dob on it for a laugh but I think I just have to wait a few months for it to dry out then tamp it down again. I think it's going to be a summer build after all. With it being completely saturated, how much do you think it will shrink as it dries out? If it rains like this again, will it swell up or stay firm if I compact it well enough?

[Bizibilder]

Your'e not going to like this  - but I feel you should shovel up all those chippings and store them until the ground has dried up.   Before you do anything else you will need to lay your blocks on concrete footings and mortar so that you can get them properly level using string and a spirit level.  Then compact the rest of the surface to ensure it is stable. Finally spreading the chippings again and compacting them as well. Time spent on preparation and leveling is time well spent   !

[MikeP]

Why not dig holes under where the blocks are laid out, fill them with concrete.  When it goes off, you could put the blocks on top with a bit of mortar to make levelling easier.  With a bit of careful measuring you could drive the angle iron down into the holes before you fill them with concrete.

Mike

PS Looks like Bizbuilder types quicker than me.

[RikM]

Yes, you're probably right. I can't lift the chippings though as I've nowhere to store them. I'll have a think about digging out for concrete under the corner blocks though; that sounds good. How deep would I have to go?

I've had a few people (including the shed guy at the timber company) say that the best way is just to sit it on some paving slabs either on slablayer or sharp sand. I wanted to raise it up a bit to get a bit more air circulating underneath, hence the blocks. I checked the level of the blocks by resting a ladder across and using a 600mm spirit level and they are spot on. I might just leave it a while and see how it sinks. It is so wet that I think if I poured concrete now, it would crack as the ground dries out.  

I have a feeling it is always going to be tough getting something 'perfect'.

[Bizibilder]

I would suggest around 4" deep for the concrete with maybe half an inch of mortar under the blocks.  If you pour the concrete quite wet it will auto-level (if you see what I mean) within its hole.  Then all you have to do is let it set and carefully mortar the blocks so everything is level in all directions.  I agree with raising the thing up to allow circulation.

Slablayer or sharp sand is OK for sheds but it does "move" over time and may cause you problems.  My own shed (garden shed that is, not observatory) is on paving slabs on slabfix (dry mix that you lay and level - it goes off hard due to the moisture in the soil).  That has been down for 10 years and is stable but it is set on 6" of well compacted hardcore !!

[Myopicus]

Hi, 

Have you used just the weedstopper membrane, or a damp proof membrane as well?  If just the former, you might want to think about putting a french drain around the obsy to minimise any potential condensation issues.

Elegant chair btw - what make is it?

m

[Ant F]

sorry to jump in here, im at the planning stage of my base.  the way i was going to do mine is basically get 6 3ft posts and concrete them into the ground to gimme some height off the ground. then im going to build my base around that. i plan on having my floor a foot from the ground and it also gives me 1ft+ more over the sheds and bushes. 

down side is i just went out and measured my plot where the 12x6 shed is going and im only left with 5 ft for the shed to roll off  

i didnt bother buying a shed with a base as i want my base hard and with not any movement.

im going to use 8foot fence posts for my base.

[Tinker1947]

sorry to jump in here, im at the planning stage of my base.  the way i was going to do mine is basically get 6 3ft posts and concrete them into the ground to gimme some height off the ground. then im going to build my base around that. i plan on having my floor a foot from the ground and it also gives me 1ft+ more over the sheds and bushes. 

down side is i just went out and measured my plot where the 12x6 shed is going and im only left with 5 ft for the shed to roll off

i didnt bother buying a shed with a base as i want my base hard and with not any movement.

im going to use 8foot fence posts for my base.

I think starting another thread might be better, getting 2 builds in one thread that are different will cause confusion ...

[RikM]

Hi, 

Have you used just the weedstopper membrane, or a damp proof membrane as well?  If just the former, you might want to think about putting a french drain around the obsy to minimise any potential condensation issues.

Elegant chair btw - what make is it?

m

At this stage it is just weedstopper. I'm going to put DPM between the (well treated) base frame and the floor boards. I will put some off cuts between the frame and the blocks as well.

The precision observing chair is an ironing stool I bought at a car boot sale for £3 It is actually a blue one of these.

[RikM]

Between levelling the blocks on Friday, the dry day yesterday and then checking the level again today, the front left-hand set where the ground was wettest, had dropped 1.5"

I ran the whacker over it for another hour early this morning and have dug in a double height set of blocks at the front, levelled (again) with a single set at the back; the garden slopes and is firmer at the back. Then I piled the spare blocks on top to add a bit more weight.  We hopefully have two dryish days ahead so I will see how much they move, then make a decision if it is worth doing anything, or simply waiting until it's dried out. If they don't move, I will dig the blocks in properly and sit them on concrete/slabmix pads to make it easier to level if nothing else. I don't really see the difference between 4" of concrete and 4" high-density foundation blocks

If they shift about and fall over, I will just have to wait until summer or until I can afford to have pilings sunk

[Tinker1947]

When i read the have "  pilings sunk " i had a vision of a giant crane with a 10 tonne block thumping iron into the ground, while this wouldn't be the case it might be easier to dig some footings, 18" wide and 18" deep should give a stable base, if it does come to piles i think 4" X 4" posts sunk into the ground on the 4 corners might  and some in between then 6" X 2" joists bolt to them to support the floor and the walls, its time consuming and not as cheap as some methods, but it will be stable and not move....

This is how i started my build, the posts are held in the ground with Peas shingle, but my ground is silty and very easy to dig a hole in...

[RikM]

I will see what happens over the next couple of days, but I think I will end up with breezeblock plinths in the corners in the end. So something like that but without the wood. The blocks are 440mm long so that should be deep enough if I drop them in end on.

[zillah]

How did you get on in the end regarding your breeze block / concrete piers? If your still undecided, I built a floating deck that sits on around 20 breeze blocks as our home is rented so I have the option of taking it with us should we ever move out. 3 years on and she's still firm and level.

Also, whilst out and about the other day, I passed the site of the new tram installation in Nottingham and they were installing new drains, yellow with about a 12" inner diameter centre. They had a stack of what appears to be off cuts in various lengths, thinking about popping back and grabbing a few (with permission) and using those, leveled and filled with concret as piers....