stumps and slabs

[big soft moose]

TNT

saying that when i was a contractor we did some work on salisbury plain and thats almost precisely what the army used to get the stumps out after we'd felled the trees ( in actual fact i think they used C2 low explosive but same difference)

made a hell of a bang and very short work of the stumps - but i dont think pikes neighbours would love him for going that route.

That was an interesting old job - amonst other things when we were strugling to get some rhodo cleared out of a valley they let us watch while they used DK79s ( a sort of a cross between a bazooka and a flame thrower) to burn it all off then we went in with chainsaws to remove the charred trunks - bloody stuff still came back the next year though :shock:

 

[frugal]

TNT

saying that when i was a contractor we did some work on salisbury plain and thats almost precisely what the army used to get the stumps out after we'd felled the trees ( in actual fact i think they used C2 low explosive but same difference)

You mean they were not felling the trees by wrapping primer (sp?) cord around them and setting it off? What is the modern military coming to. :lol:

 

[9fingers]

yeah thats all it is, i'm just wondering if others think as i do that grinding down to 10" below ground level is not suitable for laying a monolithic concrete slab over. what ever wood is left (and they are quite big tree remains up to 4 feet wide) would rot and cause instability.

i might try and dig around one and cut the roots but i'm fairly sure that is going to be way too much like hard work, especially x4!

thanks.

I really can't imagine this to be a problem. Stump grinding will leave a patch of loose soil and wood chippings. Dig this out and put hardcore in the hole and prepare the rest of the sub base as normal. Add some reinforcing steel mesh if you really want to be sure and pour the concrete.
I use the franchise firm Mixamate as a good compromise between ready mix and DIY. They mix on site and you use their barrows to barrow it in place and finish it your self. You just order the nominal amount and they mix until you have enough for the job.

Good Luck

Bob

 

[pike]

I'd have thought what's left of the stumps would cause subsidence. To be honest, I'm not that keen on a concrete slab anyway as access to the bottom of my 150 foot garden would be a bit of a 'mare. Thanks for the advice though 9fingers, sounds like a great way to do a slab if that's what's needed.

 

[Dibs-h]

Pike - I don't see a problem with grinding down to 10". In essence no matter how you remove them and how much - you're still on problematic ground.

I'd seek the advice of a structural engineer - my suspicion is that you'll end up with a reinfoced raft. An 8" slab with 2 lots of mesh - I don't think would have trouble with voids underneath.

Lets put it this way - the floor of my garage (and ceiling of the adjoining workshop, to the current one being built) will be 4m wide and 6m long - cast in situ, i.e. completely suspended, and I don't expect it to be much thicker.

You could use piles - but that would endear you even less to your neighbours.

The Homebuilding & Renovating show is on in Harrogate in a few weeks - blag some free tickets and get yourself down there - there's always some piling guys (small rigs that can go thru a house door) and have a chat. IIRC the cost per wasn't eye-watering in the slightest. That might give you options - i.e. piles and then a ring beam.

Also the chap I used for my concrete pumping does cover York and charges £150 per hour and can easily shift around 10m3 in less than 1 hour. PM me if you want his details. Also Lafarge were the cheapest for concrete - for foundations\rafts, I'd much prefer batched readymix everytime.

HIH

Dibs

 

[pike]

Dibs, thanks for that. I had to google piles and ring beams Does sound like it might be more than is necessary. Thanks for the heads up on the Harrogate show too.

I'm going to have another look at the site to be sure where I'd want footings for an on grade slab if that's the way I went.

 

[9fingers]

Hi Pike,

How big is this proposed workshop? and how much machinery are you thinking of?
I just wonder if the degree of engineering proposed is appropriate

Cheers

Bob

 

[pike]

Bob, Youre right it isn't worth going to any extreme lengths. It'll be aprox 20x10 with standard tools like band saw being one of the biggest.

I'd rather I didn't have to pour a concrete slab anyway. I'm just considering all options.

 

[Dibs-h]

Hi Pike,

How big is this proposed workshop? and how much machinery are you thinking of?
I just wonder if the degree of engineering proposed is appropriate

Cheers

Bob

I did think about that too Bob - but I just double checked Pike OP and it does read 4 tree stumps anywhere from 3' to 5' - I took those to be within the footprint of the proposed building. When (not if) the roots rot - the voids generated could be sufficient to cause significant issues to any building above (I would have thought).

Reinforced slabs are designed to span voids and I've seen a fair few designs using piles (not a sunstantial nbr) and ringbeams for even more problematic ground conditions.

Maybe I've been spending too much time with my freindly SE and everything is now supersafe. :wink:

Having said that - I'm seeing him this week, so might have a quick discussion.

Edit:

Pike - foundations (in my mind) are there to transmit the static (building\occupancy) loads along with the dynamic loads (wind, etc) safetly into the ground. The contents of your shop - will be minor in the grand consideration of things.

Foundations start getting complex as the ground conditions start getting problematic, and if the 4 tree stumps of what are\were to me mature trees are within the footprint of your proposed workshop - you are unlikely to end with un-problematic ground conditions.

 

[9fingers]

If you don't want concrete (and fair enough - it ain't very green), then an array of 3 x 5 padstones, ideally avoiding the tree sites directly, at 5' spacing, should enable a sturdy suspended floor to be constructed and timber shed on top.

Attention to damp proofing, ventilation and insulation should give a nice cosy working environment.

Bob

 

[9fingers]

Hi Pike,

How big is this proposed workshop? and how much machinery are you thinking of?
I just wonder if the degree of engineering proposed is appropriate

Cheers

Bob

I did think about that too Bob - but I just double checked Pike OP and it does read 4 tree stumps anywhere from 3' to 5' - I took those to be within the footprint of the proposed building. When (not if) the roots rot - the voids generated could be sufficient to cause significant issues to any building above (I would have thought).

Reinforced slabs are designed to span voids and I've seen a fair few designs using piles (not a sunstantial nbr) and ringbeams for even more problematic ground conditions.

Maybe I've been spending too much time with my freindly SE and everything is now supersafe. :wink:

Having said that - I'm seeing him this week, so might have a quick discussion.

Edit:

Pike - foundations (in my mind) are there to transmit the static (building\occupancy) loads along with the dynamic loads (wind, etc) safetly into the ground. The contents of your shop - will be minor in the grand consideration of things.

Foundations start getting complex as the ground conditions start getting problematic, and if the 4 tree stumps of what are\were to me mature trees are within the footprint of your proposed workshop - you are unlikely to end with un-problematic ground conditions.

Hmm! 3-5 foot stumps. I came in part way through this and missed that level of detail

Can there really be 4 off 3-5 stumps in an area for a 10x20 shed??

A site visit sounds like a good idea to mull over the options

Bob

 

[pike]

Bob: Thanks yeah pads sounds good. I'll have a closer look at the site later today.

Dibs: Actually 3 of the stumps are in the footprint potentially. Including the largest one which is aprox 4 feet wide at the surface and bigger below.

 

[Dibs-h]

Dibs: Actually 3 of the stumps are in the footprint potentially. Including the largest one which is aprox 4 feet wide at the surface and bigger below.

Sounds like the entire area under your shed is likley to be full of roots - I think you are going to end up with something other than a simple solution.

 

[pike]

I've been out with a tape again and if I don't want to completely waste the bottom of the garden I'd need to build over the stumps area. The perimeter could be outside of the stumps but yeah dibs it would still be full of roots. Perhaps I can get them ground down, only have floor not footings right over where they are and saw any roots away where I want footings?

I've either got to work out how to deal with it or I'm looking at a smaller workshop in the wrong place for me.

I like the idea of piers. Maybe I just do a grid of carefully placed concrete pads and sit a timber floor on piers? There by only having to sort roots out in those areas rather than the whole run of footings?

 

[big soft moose]

I've been out with a tape again and if I don't want to completely waste the bottom of the garden I'd need to build over the stumps area. The perimeter could be outside of the stumps but yeah dibs it would still be full of roots. Perhaps I can get them ground down, only have floor not footings right over where they are and saw any roots away where I want footings?

I've either got to work out how to deal with it or I'm looking at a smaller workshop in the wrong place for me.

I like the idea of piers. Maybe I just do a grid of carefully placed concrete pads and sit a timber floor on piers? There by only having to sort roots out in those areas rather than the whole run of footings?

that would work - but i would be cautious about regrowth coming up under the shed from the roots and stumps

if its a long term investment i still think that if its worth doing its worth doing right even if that does involve a lot of navvy work to remove stumops and roots first - course what you really need is a minidigger - but presumably your access issue preclude that idea ( a mate of mine with similar issues had the mini digger craned over his house - but that was not cheap)

 

[pike]

it's true it's always worth doing right, but after a year without anywhere to work i've run out of patience :-|

i was hoping that the stumps ground down and covered shouldn't come back ... starting to doubt that statement already..

 

[Dibs-h]

You can get mini\micro diggers that you can drive in thru the front door and out the back - I was thinking of one beacuse our side gate is only 900 wide (which is what they require). Drove a normal one down next door's drive and across both gardens in the end.

Not as much oomph as a normal one - but damn sight easier than by hand.

What you are suggesting is in essence something the size of a normal garage - does it need PP or B Regs approval?

Also - I would do it right, you could end up with some right hassle if it goes pear shaped. IIRC the mini pile people (I saw at Harrogate last time) were quoting <£100 per pile based on 10 piles. Can't remember much in the way of detail - but I'll be at the show so will make a note to ask and get some literature this time.

 

[big soft moose]

it's true it's always worth doing right, but after a year without anywhere to work i've run out of patience :-|

i was hoping that the stumps ground down and covered shouldn't come back ... starting to doubt that statement already..

poplar has a nasty tendency to sprout from the roots - were the stumps treated with glyphosate when the trees were felled - if so you'll be fine - but if not if you are leaving the roots in if you are building on peirs at least youl be a be able to get under the shed with a spray wand if/when they do resprout

 

[wizer]

Can youu not buy 'Root Out' anymore? Ammonium Sulphate iirc

 

[pike]

I think it's ammonium sulphamate. you can, that would help, good idea thanks. of course it takes a long time to work and I doubt I'd get every last bit of the poplars with it.