The Brew Cabin

Posted: **Mon Sep 10, 2012 5:36 pm**

Hi everyone - first post from a newbie and I hope you can advise me!

Problem: My home is built on a side slope (right to left as viewed from the road) and the concrete path alongside the property to the road has slipped partway over time to become a significant tripping hazard. The path is built in 7 bays of approx 7 - 10 feet lengths, 3' - 3'6" wide with expansion joints between each bay. The main area of concern is from the corner of the building to the road. The 1st bay (counting from the road) has dropped at the first joint about 3" and also tilted in the direction of the slope.

The house was built in 1961 and the path looks original. The fault appears to be either poor initial workmanship or water percolation underground eroding the sub-base. Or both. I've lived here for 3 years and the slippage looks to be historic with no apparent further movement in that time.

Possible solutions: Break up path and re-lay from scratch. (Time consuming and expensive - not preferred)

Stabilise base, overlay with new flags. (Time consuming, expensive with a lot of cutting involved due to measurements etc - not preferred)

Re-skin with suitable concrete mix (I'm thinking approx 25 - 30mm skim with fine granite chips as the aggregate and dye mixed in the cement - cheaper option, no cutting involved and hard wearing surface - preferred). If this method is feasible, would I need to take into account the expansion joints (and re-skim to these) or could I safely lay over them to form a completely watertight surface?

An added complication is bay 2 which has a sewer inspection manhole in it. This section hasn't moved, probably due to the brickwork chamber below supporting it. The manhole cover is the old, very heavy, rutile iron type, the frame of which would be very difficult to remove. Would it be possible to install a modern, lightweight one directly above it provided I put in adequate supports across the original hole?

I do need to rectify this issue fairly quickly and would appreciate any advice on the best course of action. I'm an experienced DIYer and no stranger to laying concrete and flags and building garden walls etc.

Thanks in advance,

Rich

Posted: **Mon Sep 10, 2012 10:27 pm**

You will not succesfully bond that thin a layer to the underlying one. A 75mm thickness would be the minimum for concrete and even then it might crack.

It would work indoors as a bonded sand and cement screed but that wouldn't be suitable outside.

I think you know the answer is to start again.

Resin bonded gravel might be possible but it would show any cracking or movement of the old concrete through to the new surface and i'm not sure it would be suitable to take up the large depths needed to level out the fallen areas.

Posted: **Tue Sep 11, 2012 6:55 am**

Re do it, if not preffered option may be best to live with it as anything else is a bodge.

Posted: **Tue Sep 11, 2012 8:23 am**

post some photo's first.
Sounds like a complete dig up and redo, anything else would be a bodge and wouldn't last.

Posted: **Thu Sep 20, 2012 11:44 am**

You can bond a thin screed onto the concrete, but if the concrete base is moving, then the screed will follow.

One of the thin screed options is:

Ronafix Pre-Packed Screed

Posted: **Tue Oct 02, 2012 3:03 pm**

Hi All, and thanks to everyone who replied. Sorry there are no pics but I'm not that savvy on how to upload them!

In the end I bit the bullet, hired a concrete breaker and dug the offending sections up! I discovered the reason for the slippage - the concrete was a minimum of 6" thick! No wonder it moved given the thinness of the sub-base - a bit of overkill I'd say for a garden path, I could have driven a lorry over it!

I've prepared the formwork, laid a good rubble base with an average depth left of 3" for the new concrete and left a deeper edge of 9" deep x 6" wide bordering the garden for extra support on that side. Now I'm just waiting for the weather to improve!!!

I have another query, if I may?

The old path has expansion joints every 8ft or so and is approx 3ft wide. Only the first section (from road to house) has an open side - that is, bordering the front garden, the remainder is between house wall and garden wall. Would I be better to follow the original construction and build in expansion joints, or would I be ok to in-fill completely without them? Also, I'm thinking a 6 to 1 all-in ballast to cement mix - would that be adequate for foot-traffic only?

Thanks again for any advice

Rich

Posted: **Tue Oct 02, 2012 5:31 pm**

the expansion joints are probably more to do with crack control because the pads are long and narrow meaning they're easily broken over longer runs so I'd keep it the same. If you can it would save all manner of ball aches using ready mixed concrete mixing large quantities on site isn't fun and the concrete can look patchy.

Posted: **Tue Oct 02, 2012 5:39 pm**

Rubble base? err I think you meant to say thoroughly compacted MOT Type one? That was probably more likely the reason for the previous path failure

Posted: **Tue Oct 02, 2012 6:56 pm**

we find paths etc on old council houses tend to be 150 thick on top of brick hardcore

this type of slippage is not uncommon especially if a gutter has leaked at some point
chances are its sunk as much as its going to sink
just give your rubble a good wack with a wacker
ps concrete should be 100mm thick
LLL

Posted: **Wed Oct 03, 2012 8:32 am**

Thanks again guys for the speedy replies!

Rubble base? err I think you meant to say thoroughly compacted MOT Type one?

Yes, you're right. All the old broken concrete has been removed and will be used as infill in the rear garden (next job!)

If you can it would save all manner of ball aches using ready mixed concrete mixing large quantities on site isn't fun and the concrete can look patchy.

I've only broken up 2 sections of the old path - about 30ft in total. Due to the positions of the drains, I have to recast one section in 2 parts to provide adequate fall (in opposing directions) so the mixing wont be too bad and I have a petrol mixer. (And a handy wife!)

we find paths etc on old council houses tend to be 150 thick on top of brick hardcore, this type of slippage is not uncommon especially if a gutter has leaked at some point

This was the same! These houses (though privately built) are 1961 vintage so I assume that was the thinking of the day back then? Point taken on the thickness.

I realise that the finished job will look very 'new' compared to the old concrete but I intend to replicate the finished surface as best I can (brushed off top surface to expose ballast). One thought is to use some sort of concrete stain on the whole path once the new has hardened off to at least help disguise the new sections. Any thoughts?

Once again, thanks for your expert advice!

Rich

Posted: **Wed Oct 03, 2012 7:29 pm**

there are ways of exposing the aggregate rich but they are probably beyond your remit
just accept that you have a new bit and it will soon blend in
i did some patching in my side alley 7 years ago and it hardly shows now
LLL

The Brew Cabin

Old concrete path problem