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Posted: Tue May 13, 2008 2:23 pm
by rushd
Continued DIY block paving...
I am pondering how best to adjoin with the existing driveway. Any advice appreciated.
I have now laid my concrete edgings on all sides except the side that meets the existing (tarmac on concrete) driveway.
No I didn't want to take the existing driveway up... 
The haunching from the existing driveway slopes down in to my excavated area, and I am intending to leave this haunch in place because it's solid concrete and this area will be the only side that cars will access the newly paved area, ie. it is the threshold and needs to be strong. The haunching encroaches/slopes into my excavation by no more than 20-30 cm.
I am wondering whether to
a) concrete the edge blocks along the top of the existing haunching, or
b) chip the level of the existing haunching down so that I can bed these edge blocks on sand as per the rest of the paving body
Could anyone offer me advice as to the best option to take please.
But please don't say 'take the haunching out...' haha
Thanks in advance
Posted: Wed May 14, 2008 10:28 am
by rushd
bump
Posted: Wed May 14, 2008 5:39 pm
by Rich H
The blocks that you lay against the existing drive will need to be set in concrete. If you have room between the top of the old haunching and the underside of the edge block it should be fine. You might want to consider an admixture to the mix to help it adhere to the old haunching, which will need to be scrupulously clean.
You might also want to consider adding a strip of bitmac between your existing drive and the edging blocks - that way you can ensure a sufficient haunch on both sides of the edging blocks.
Posted: Wed May 14, 2008 9:15 pm
by lutonlagerlout
if you have flexible and non flexible pavement s adjacent its asking for trouble better to take the haunching out and concrete a 150 mm edging in its place,that way there will be a delineating line between the two
LLL
Posted: Thu May 15, 2008 11:14 am
by rushd
many thanks for the replies guys
i should've mentioned that the edge of the existing driveway has flush edging concrete kerbs in place, and the haunching is holding these in place to 'frame' the tarmac drive. the haunching looks to be a significant mass of concrete, especially closest to the road which is where most of the stress occurs i guess? this would be the access route to the newly paved area.
so i think, in digesting the info you have given me....
i have a delineating line separating the two pavement areas as the existing driveway has these haunched kerbs in place.
as this driveway has stood the test of time for 10 years with the haunch in place, i'm inclined to concrete my new edging blocks on top of it, having cleaned the haunching concrete....
should i clean the existing haunch with Acid 'stuff'? or just water and a scrubbing brush?
by 'admixture' for concrete, I assume that a BM would know what I was asking for....?
a final thought, there are stones in the ballast/concrete which may make the bedding of the edgings awkward due to a lack of depth from the top of the existing haunching to the finished paving level, could I use a strong mortar..... ie "concrete without the lumps" haha ?
any suggested product-names that you trust would be appreciated
hoping for some further wisdom
cheers
Posted: Thu May 15, 2008 5:27 pm
by Rich H
You could use a strong sharp sand mix if the depth is shallow, and as you'll have it on site anyway for the main paving. You don't need to acid wash the haunching - a hose and brush will be fine. You could use PVA as an admixture - the container will have instructions on the quantity to add to water for the mix.
LLL's concern is that you'll have a flexible drive next to a solid one. The flexible drive will sink a tiny amount (hopefully tiny anyway) over time and this can leave the edging blocks standing a couple of mm 'proud' of the main paving area.
Posted: Thu May 15, 2008 5:53 pm
by rushd
thanks Rich H
i can understand what you and LLL are saying, but to my mind this means that a flexible paving body would eventually sink (a little) from any/all concreted edgings, whether constructed as per the info on this website or constructed by bending the rules a little, such as I am attempting?
All of these edging examples shouldn't move, so is there any difference between
a) a concrete edging constructed as a free edge (as per the info)
b) a 'restrained' edge... against a house or kerb (as per the info)
c) a concrete edge concreted onto existing concrete haunch such as I am hoping to do
should I try and leave the paving body a few mm proud to begin with, to try and compensate for the anticipated sinkage?
blimey, feels like it's getting techie now
this project came about because we wanted the tidiest solution to extending our parking area without effecting the existing driveway. but we don't like gravel....
cheers
Posted: Fri May 16, 2008 5:21 pm
by rushd
bump
Posted: Fri May 16, 2008 10:21 pm
by Rich H
There's no practical difference between a) b) & c). The only issue is that you will have have two different construction methodologies alongside each other. Flexible paving is very strong and suitable for most applications but it does behave differently to rigid construction. In your situation I wouldn't set out to compensate for potential minor sinkage because you can't realistically predict where and when and by how much!
It sounds as though you're going about things the right way so I wouldn't worry. Lay everything to the design levels as planned. Make sure the sub-base is well compacted and the bedding course of sand nice and even and well screeded. If the main paving drops 2mm over the next few years it's not the end of the world.
Posted: Mon May 19, 2008 10:26 am
by rushd
thanks for your thoughts Rich.
scrubbed the existing haunch with a wire brush and put some PVA in the mix.
hopefully it'll stick
cheers
Posted: Tue May 20, 2008 12:14 am
by matt h
better off using SBR, thats what its for:)
Posted: Tue May 20, 2008 11:25 am
by rushd
oh sh1te, too late now Matt.
oh well PVA has gotta help.... hopefully ???
Posted: Tue May 20, 2008 3:50 pm
by Rich H
It will. That's what it's for, too.
Posted: Tue May 20, 2008 4:08 pm
by rushd
haha glad to hear that Rich
thanks for your advice
it reassured me to think that even though I wasn't sure that I knew what I was doing, that somebody else with a better knowledge than me had given it the ok...
cheers
Posted: Tue May 20, 2008 4:14 pm
by Rich H
Christ, that's torn it.:p