crack in garage floor due to old tree/stump left - any idea of cost for removal?

[passionsrunhigh]

been told that if the tree stump gets larger (tree was taken down about 5-10yrs ago) there will be more cracks in the garage floor which can destroy the structure. One large crack made the foor uneven though useable. There are also shrubs around right next to garage so not sure if they are not causing same. Surveyor told me to do the work asap as i need garage for storage so don't want any damp appearing (or to lose the garage eventually!). To me it sounds almost impossible to dig out the roots of the stump, as he seemed to suggest. How much would this cost and who best to do the work? Is it even possible, or the surveyor sugar coating it? The floor is concrete and if needs relaying after the work - what's the cost of that? grateful for advice!

I had a tree stump ground down, which cost £70. It was left at about 8 inches below ground level. The roots are still in the ground though, not sure how they would have removed the whole thing.

thanks, Miss. It's the roots though that raised the floor and caused a crack - do you think grinding down help roots not develop/move? did it effect any structure in your case?

No structural problems that we're aware of. How about reposting this in Gardening, they're very knowledgeable over there.

In our case the stump grinding didn't kill the tree (foliage is now poking out of the ground), so I assume the roots are still growing. Our tree is a Cordyline, which has a rather particular structure, the roots are very fibrous, and the tree surgeon warned us the regrowth could happen.

It would make sense to me that you need to kill the tree first, and then investigate a more aggressive stump removal than we did. Sorry to not be much help!

are you saying that the floor has started to crack after the tree was cut down?

This is more characteristic of ground heave, common on clay soils. What happens is that the old tree used to suck moisture out of the ground, making it shrink. When the tree is cut down, the ground gradually absorbs water again and expands back to its "normal" size. If the garage was built when the tree was big, it will have been built on shrunken, subsided soil, and it is going to get pushed up when the soil expands again.

I am going to guess that the garage was built on a simple unreinforced concrete raft, possibly with thickened edges under the walls if brick. Unlike a house foundation, it will not have been dug deep enough to avoid heave, it is just lying on the surface, or maybe six to ten inches deep.

If my guesses are correct, then I don't see that you can do anything to stop the ground heaving and lifting the garage floor. You might consult a builder about having the concrete raft broken up (except under the walls) and some paving slabs laid on sand on a dpm, at least this will not suffer any serious damage from heave, though it may bulge a bit and become uneven. In which case the slabs can be lifted, and relaid after levelling the sand.

It will take several years for the ground to finish moving, no point in spending a lot of money repairing if it's going to move again.

As regards the stump not being dead, you can carve a bowl into it and fill it with SBK brush killer or other chemical, which will soak in and kill it (protect from rain). You can have it chipped if you want, but still need to kill any regrowth or suckers by cutting them off quickly and dabbing SBK or Glyphosate on the stumps. The roots will NOT grow bigger now the tree has been cut down, they will gradually rot away (this may take 20 years or more)

MissHonk - thank you,n posted in Gardening too.
PigletJohn, thank you for such an informaive response! now i understand what the problem is (not the stump as such). You guessed correctly, It looks like the garage was built when tree was still up (though I'm not 100% sure - they might have cut down the tree in order to build these few garages in the forcourt of hte building), In any case the tree was active at that point and the grouns affected as you say. Also correct about simple concrete floor, the rest is of 'rendered block constructuion' i.e. walls - I don;'t knowwhat that means, timber? the surveyor suggests that trees and shrubs (there aer some small ones around) and the stump can get bigger so should be removed. Surely this means taking up the floor. Thank you for suggesting slabs - this may well work - do you know the approx cost for this? and even if the floor is fixed like that, wouldn't the walls crack if ground raises again?
Will rotting roots cause damp?

ah ok, the read about using chemicals so no need to raise the flooor but still worried whether rotting roots will cause damp.

I meant 'just re-read'

if the floor heaves and cracks any more, breaking it up will reduce the risk that the floor will lift the walls and crack them (rendered blockwork is lightweight concrete blocks, about 4 times the size of bricks but cheaper and quicker to build with). The rotting roots will not cause damp, but if near the surface will leave hollows in the ground (I had a diseased tree taken down, and the lawn has sunk in lines where the roots rotted away).

You can paint or photograph the ends of the cracks so you will be able to see if they get any longer.

A couple of strong lads with a big grinder (to groove it near the walls) and kango hammers or similar could break up the slab in an hour or two, it might take another half day to hump the bits into a skip, and not more than another 2 days to lay sand, vibrate it flat and lay slabs. It is building work but not highly skilled. You need someone local and reliable. It is very similar to replacing a cracked patio, except that the slab may be thicker and it is out of the rain. A garden contractor looking for an indoor winter job might do it.

Omitting a dpm will mean the floor is damp and you will get condensation and rust on things in the garage.

If you're unlucky you might get some cracking in the walls as well, in time, but the floor will be worst affected by heave. Best not to lay a new concrete floor until you have reason to believe that all movement has stopped.

Is that why the insurance company ask if you have trees within 7 metres of your property?
passionsrunhigh I take it the garage isn't attached to the house? I only mention as our house had subsidence 23 years ago and even though all sorted out obviously at the time, our insurance is a complete nightmare - you can't even get standard contents cover if you have had subsidence or "heave" in case the building falls down and squashes all your stuff.
Make sure your insurance co are aware if you need the stuff in your garage covered - most places want a structural engineers report within the last 12 months - which you currently have - so something to bear in mind.
I ended up in some twilight zone of the insurance world when i tried to change insurers recently...

I don't know what the insurance co rules are for trees. As a rule of thumb it's often assumed that you are at risk if the height of the tree is greater than the distance away from your house, but some trees are thirstier than others, and some soils are more shinkable (especially clay) and some houses have deeper foundations, so it must all vary.

If you have a subsidence claim I understand it is easier to stay with the same company as it avoids two or more companies arguing over who was at risk when the damage occurred.

Oh yes, most of my road just stay with their original insurer but my quote was just taking the mickey this year. I found one, after a whole week on the phone, £300 less and that's with full subsidence cover and everything down to the cat having wind declared. Most of the town subsided in the late 80's so it's not exactly unusual here

Piglet, what's the best way to kill my hideous cordyline? Above ground it's just sword-like leaves that grow in a thick spike. Should I drill holes in it and try to syringe the stuff in?

have a look at a bottle of SBK. It usually says crush the leaves and put it on, or cut off stems and put it on the stump. Similar to the instrs on Glyphosate. Some people unwind creepers and push them into a bucket of weedkiller to immerse the leaves.

SBK is described as brushwood killer, it does not seem to kill grass so you can use it on suckers that come upo through lawns. It is quite strong
www.google.co.uk/search?hl=en&q=sbk+brush+killer&meta=

I managed (eventually) to kill ivy by cutting it back to stumps and dabbing Glyphosate on them. Ivy is very difficult to kill as the leaves throw off weedkiller. I haven't had a cordyline.

p.s. I have had garden yuccas 12 foot high which might be comparable. I cut them off and poured glyphosate onto all cut edges. When they resprouted I cut the sprouts off and applied glyphosate with a small paintbrush. When gardening I chopped the stump about with a spade and applied more glyphosate if I saw any signs of life. The stump is mostly rotten now (took three years)

I had to use a saw but it is not as hard as a tree.

Three years????!!!!!

Piglet you are truly a treasure trove of advice!

pepper - garage is not attached, but very near. It's flat not my own house, so not sure whether building insurance would extend to the (three) garages owned by flats.
PigletJ - (that was my other name)you truly are a treasure trove! The thing with slabs is that if later used for a car it will need some slope to get higher than the ground level. But I could use slabs while having it for storage, and if selling later people can remove them easily i assume. Surveyor now says there is no heave, but it's raised uneven crack. Just worried that the damp can come in through it?

yes it can.