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Posted: Wed Nov 07, 2007 1:10 pm
by Sqwim
Hi, getting towards the stage of screeding for my DIY block paved drive widening project. I have had to install a recessed manhole cover and have a query about how to screed round it.
Due to the recessed manhole cover being concreted in, the area directly around the manhole cover will have a more shallow screed depth (thickness of sharp sand) than the rest of the drive (I'm using 60mm blocks and there's about a 75mm gap between the top of the manhole cover level and the concrete fixings, leaving about 15mm of space for the sand).
How do I best deal with this in order to ensure the blocks over it remain level with all the other blocks and do not sink (or rather 'hump') due to the different screed depth? The concrete fixing extends about 50mm outwards if that helps.
Thank you, I'm all ears!
Cheers.
Posted: Wed Nov 07, 2007 1:38 pm
by surreyhillslandscapes.com
I would screed as normal running the block around the cover 5 to 10mm above, if they are sitting a little proud after compaction then maybe a little gentle persuasion with a rubber mallet, little tip, use tractor grease between the cover and frame, it stops too much kiln dried getting in the gap and make it a lot easier to get out should you need to.
Posted: Wed Nov 07, 2007 4:52 pm
by Rich H
Rather than have the blocks half-on half-off the rigid base around the MH, consider laying the solids and cuts to the rim on a mix. It will make the sand prep up to these blocks a bit tricky, but you don't want a block with 15mm of sand under on one side and 40-50mm on the other.
Per the above, the blocks laid on the full sand bed need to be proud of the concreted ones, but 5mm is enough I'd say 
Posted: Wed Nov 07, 2007 8:21 pm
by Sqwim
SurreyHillLandscapes - so will a rubber mallet cause more compaction than a whacker plate?! I assumed that would not be the case!
Rich H - I presume you mean a cement/mortat mix rather than a dry mix?
Hmm, now I'm really not sure what to do!
Posted: Wed Nov 07, 2007 10:58 pm
by Rich H
sqwim> whatever mix you used to secure the recess tray. What I'm saying I suppose is try to avoid that thin layer of sand; 15mm won't compact the same as 40-50mm.
Posted: Thu Nov 08, 2007 5:22 pm
by surreyhillslandscapes.com
Works for me,but then I do have a very big mallet, if it's really stubborn then lift any that are sitting a little proud remove a little sand from underneath and tap down with a rubber mallet, Rich has a good idea there also ..
Posted: Fri Nov 09, 2007 6:01 am
by lutonlagerlout
good question and i have asked many people this before without a satisfactory answer
i suppose unless you can get a cover with 150mm profile so that sand is even you will always get some lumping after a few years
all the above fixes are short term ,but i suppose most important is to make sure you use terram and make sure your sub base is well compacted to alleviate any settlement
good luck
LLL
Posted: Fri Nov 09, 2007 11:44 am
by surreyhillslandscapes.com
Very true, I've lost count of the amount of driveways I've seen with a manhole sitting halfway out of it.
Posted: Fri Nov 09, 2007 8:58 pm
by De1b0y
Front drive going well; wish I had more time to get on with it.
I read the forum topic on screeding around manholes and have read the section on recessed trays.
Are there two schools of thought on when to install the tray/manhole?
The site topic discusses putting in the recessed tray once it is already virtually surrounded by blocks (using the surrounding blocks to give the manhole level) whilst the forum seemed to be discussing putting the tray/manhole in first.
I am about to install a recessed tray.
I have already completed the border blocks around the whole drive area and had intended putting in the tray next before I started to do any screeding and blocking.
Can someone indicate what would be the best time to do the tray/manhole?
Many thanks
De1b0y
Posted: Fri Nov 09, 2007 9:43 pm
by James.Q
lay blocks then fit man hole cover works every time
Posted: Sat Nov 10, 2007 7:17 am
by Dave_L
James.Q wrote:lay blocks then fit man hole cover works every time
Yep, that's the way I'd be doing it too
Posted: Sat Nov 10, 2007 3:47 pm
by De1b0y
Many thanks.
Great advice.
Best regards
De1b0y
Posted: Sat Nov 10, 2007 4:03 pm
by De1b0y
And then..........
OK first lay blocks surrounding manhole position, then install manhole.
But.........
Following on from earlier comments in this posting, should the final blocks surrounding the manhole be laid on a bed of mortar? Otherwise one end of these blocks will be sitting on the 'haunches' and the other on the compacted screed.
Regards
De1b0y
Posted: Sat Nov 10, 2007 4:42 pm
by seanandruby
If you haunched it correctly it shouldn't. Your haunching should be angled so that you can lay on a continuous bed. May be easier to break out the surround and redo it. At least you only have one manhole to do, Ive been on jobs were bods have backed kerbs up so high that hundreds have had to be reduced to accommodate paving. Is the haunching to wide for you to undercut the blocks?
Posted: Sat Nov 10, 2007 4:57 pm
by De1b0y
Hi Sean
I am fortunate that I have to take a course of bricks off the old manhole to accommodate the greater height of the recessed manhole. I can then haunch it as you suggest and do the surrounding blocks on a screed base.
Many thanks
De1b0y