DundeeDancer Posted August 2, 2017 Share Posted August 2, 2017 (edited) Hi, wondering if anyone would know roughly how much effort/cost it would take to core a 80mm hole through a double thickness concrete block wall. Might need up to 6 cores done to make room for a retro-fitted MVHR system. Structural engineer thought it would not have an impact on structural strength on building, so from that viewpoint it can be considered. So now wondering about cost and effort. Thanks, DD Edited August 2, 2017 by DundeeDancer Tidy up. Link to comment Share on other sites More sharing options...
jamiehamy Posted August 2, 2017 Share Posted August 2, 2017 Hire a core cutter and you'll have it done in a day. If you can do it from the outside the have an assistant pour water on it to make it much more pleasant. If no rebar then around 15-30mins each? I'll dig out some pics for you - we had to do 5 through heavily reinforced concrete, one wall being 500mm thick... Goggles and ear defenders an absolute must. 1 Link to comment Share on other sites More sharing options...
jamiehamy Posted August 2, 2017 Share Posted August 2, 2017 Ah yes - something I hope never to have to do again! 60year old concrete with copious amounts of rebar! 2 Link to comment Share on other sites More sharing options...
PeterW Posted August 2, 2017 Share Posted August 2, 2017 22 minutes ago, jamiehamy said: Ah yes - something I hope never to have to do again! 60year old concrete with copious amounts of rebar! .... and no your honour I was nowhere near Hatton Garden and my name isn't Boris..... 1 Link to comment Share on other sites More sharing options...
Temp Posted August 2, 2017 Share Posted August 2, 2017 80mm is quite small for a MVHR duct. Link to comment Share on other sites More sharing options...
Alexphd1 Posted August 2, 2017 Share Posted August 2, 2017 (edited) https://www.hss.com/hire/p/light-duty-dry-diamond-drill-110v and buy a https://www.tool-net.co.uk/p-347664/tool-net-91mm-x-150mm.html?gclid=EAIaIQobChMIz7O8ldG41QIVbLXtCh0qrgstEAQYAiABEgJpOvD_BwE Job done! The hire one comes with a 107mm core. If you do hire that makita keep the core drill dry. Edited August 2, 2017 by Alexphd1 1 Link to comment Share on other sites More sharing options...
DundeeDancer Posted August 2, 2017 Author Share Posted August 2, 2017 Thanks for the replies so far. Won't be me making the holes, it will be the building contractor I get in. This is investigation work into the layout of the MVHR system that I am discussing with my architect. Due to the 200mm central concrete wall down the middle if the apartment. Plan A is making 5 or 6 holes for the 75mm ducting or as my architect is currently suggesting Plan B two separate MVHR systems running all the time. So 3 to 4 hours work doesn't sound to bad for the new holes. If it was going to 20 hours plus and really tough going then Plan B it would need to be, but Plan A is currently still alive Link to comment Share on other sites More sharing options...
jamiehamy Posted August 2, 2017 Share Posted August 2, 2017 Fwiw, BPC initially specced two MhRV units but we ended up going for a single Hi Flo unit. Aside from cost saving, this was significantly easier to install - I dread to think what sort of space wasting spaghetti junction might have been required otherwise! 1 Link to comment Share on other sites More sharing options...
Onoff Posted August 2, 2017 Share Posted August 2, 2017 3 hours ago, jamiehamy said: Ah yes - something I hope never to have to do again! 60year old concrete with copious amounts of rebar! I trust you've saved and varnished some of those cores for use as decorative paperweights / doorstops / keepsakes? 1 Link to comment Share on other sites More sharing options...
Onoff Posted August 2, 2017 Share Posted August 2, 2017 Minimum cost: http://m.ebay.co.uk/itm/80mm-SDS-TUNGSTEN-BRICK-CORE-DRILL-HOLE-CUTTER-PILOT-BIT-SDS-SHANK-ARBOR-/263083129777 They DO work but you have to drill to it's depth then break/bolster that bit off. And sometimes make an extension bar: I thought I'd never get through those footings when I brought the new water main in but I did! 1 Link to comment Share on other sites More sharing options...
Pocster Posted August 2, 2017 Share Posted August 2, 2017 I've seen some cheapest diamond core drill bits for diy that claim can go through the rebar . Anyone tried these rather than hire ?? Link to comment Share on other sites More sharing options...
Onoff Posted August 2, 2017 Share Posted August 2, 2017 9 minutes ago, pocster said: I've seen some cheapest diamond core drill bits for diy that claim can go through the rebar . Anyone tried these rather than hire ?? I've either got re-bar bits from Hilti in the past or if desperate used a Starrett for the bar when the masonry bit hits steel. Best option is to design so you don't need to drill where the re-bar is! Link to comment Share on other sites More sharing options...
Pocster Posted August 2, 2017 Share Posted August 2, 2017 40 minutes ago, Onoff said: I've either got re-bar bits from Hilti in the past or if desperate used a Starrett for the bar when the masonry bit hits steel. Best option is to design so you don't need to drill where the re-bar is! Lol the rebar is everywhere !!!!! Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 2, 2017 Share Posted August 2, 2017 Diamond core drills will go through rebar with not much extra effort. Drilling goes noticeably slower when you get to one, or more than one, and you just use high revs and next to no pressure to allow the bit to progress. I would, without hesitation, hire a drill that comes with a water feed system that squirts water down the pilot bit, IF these were bigger holes, but at ~80mm I'd just drill them dry and accept the bits as consumables. A good machine is essential, one that can keep going for the whole duration without cooking itself to death. That said, hiring the drill is best so you get an expensive machine for minimal outlay, plus you get to give it back at the end . Link to comment Share on other sites More sharing options...
PeterW Posted August 2, 2017 Share Posted August 2, 2017 +1 to what @Nickfromwales said. I hire core drills as I nearly broke a wrist using an ordinary SDS drill with a core set and it snagged on rebar - proper core drills have decent clutches that stop the drill trying to rotate you through the wall when the core jams ..... 1 Link to comment Share on other sites More sharing options...
Vijay Posted August 3, 2017 Share Posted August 3, 2017 11 hours ago, pocster said: Lol the rebar is everywhere !!!!! Why so much rebar? Link to comment Share on other sites More sharing options...
Pocster Posted August 3, 2017 Share Posted August 3, 2017 (edited) 4 minutes ago, Vijay said: Why so much rebar? It's structural. Specified by the SE. 11 hours ago, PeterW said: +1 to what @Nickfromwales said. I hire core drills as I nearly broke a wrist using an ordinary SDS drill with a core set and it snagged on rebar - proper core drills have decent clutches that stop the drill trying to rotate you through the wall when the core jams ..... Yeah I was wondering if when I hit rebar my wrist would snap.Thing is I might have quite a few to drill; doing them all at once isn't a problem. Getting them all the the right place in advance is . I am making this up as I go along you guys know! So my logic was to buy a cutting head that flea-bay claims "even cuts through rebar - no problem" and just see. Can always send it back if it doesn't cut rebar and once my broken wrist has healed .... Edited August 3, 2017 by pocster Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 3, 2017 Share Posted August 3, 2017 Has the concrete been cast yet? Link to comment Share on other sites More sharing options...
Ferdinand Posted August 3, 2017 Share Posted August 3, 2017 (edited) 3 minutes ago, Nickfromwales said: Has the concrete been cast yet? 110mm soil pipes can be very useful things if applied first. If we had 80mm ducts and a really good detector in my dreams we could core between the rebar squares. Edited August 3, 2017 by Ferdinand Link to comment Share on other sites More sharing options...
Vijay Posted August 3, 2017 Share Posted August 3, 2017 are you building in ICF? Link to comment Share on other sites More sharing options...
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