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you could try glass fibre, its strong, light and wont corrode
The latest in my occasional series of “building project conundrums”.
In short, and I know they aren’t ideal, but I’m having to have a manhole inside the house. It’s going in a short ground floor passageway. I have two drains converging at a Y to the final run down to the public sewer and I need rodding access in three directions. Plus I have extractor ducting and motor for the basement pool running through the void which I’ll also need occasional access to. No open drains so the manhole doesn’t need an airtight seal.
But it’s inside the house, in a passageway with an original marble floor. So my plan is, rather than hide it, to make a feature of it by having a custom made frame and tile-able cover made in stainless steel, with a geometric marble design in the manhole itself. I can then incorporate a matching design, sans manhole, in the passageway’s twin on the other side of the courtyard. On the manhole side the border will be visible of course plus a triangle section in each corner so that a willing assistant at each end can insert a pair of manhole keys to haul the thing out of the way when required. It’s going to be heavy for sure - the cover will be around 600mm x 1000mm.
My plan is to get it made by a local stainless fabricator who has done custom made work for me before.
I can’t decide what will be the best material for the actual base that will sit inside the cover’s perimeter. That is the part that needs to be tiled. It needs to be very stiff, inert (due to humidity, which rules out plywood) and as light in weight as possible (I’m sure a glued lamination of cement board would be strong enough but would make the whole affair hernia-inducing, which I’m trying to avoid).
There has to be a suitable sheet material- hopefully the collective wisdom here can help.
Last edited by draftsmann; 27th April 2021 at 08:28.
you could try glass fibre, its strong, light and wont corrode
Stainless stell sheet seems the obvious material?
Glass fibre is a good idea. But do you really want to tile it?
It’s likely to be what makes it heavy, and fragile.
You mentioned making a feature but you are effectively hiding it, if I understood correctly.
You might want a cone, or a pyramid from the same stainless steel maker for example. Hollow, it would be light enough…
'Against stupidity, the gods themselves struggle in vain' - Schiller.
Perspex.
Thank you gents.
It has to be flush to the floor as it’s a walkway.
I hadn’t thought of GRP- that might be an option although it isn’t light if it’s laid sufficiently thickly to carry foot traffic without flexing. That said there might be some scope for doing something clever with box sections, which I think would be a better way to go.
Stainless won’t be a good base for tiling, plus expansion/contraction as temperature fluctuations are fierce here, and would be hideously expensive and heavy if sufficiently thick not to flex.
Glazing is an interesting thought. Not acrylic or plastic as it would scuff and scratch in no time and not clear glass as this isn’t a beautiful old well but a pit full of services. Maybe an opaque white frosted glass- 18mm thick would be plenty stiff and strong enough for foot traffic.
I’m also thinking though whether a sandwich of half-inch cement board bonded to a filling of Kingspan or similar might work. I remember seeing an article in a woodworking magazine a long time ago about box section bookshelves made with outer skins of just 1/4” ply.
One other possibility is to look out for an original decorative cast iron manhole. Or even, if you don't need human access, a coal chute cover:
https://www.ebay.co.uk/itm/393247496...QAAOSwz~ZfX9o7
which are usually a 12 inch diameter. There's some lovely Victorian ironwork out there. You could even get something knocked up in brass or bronze which would be polished by walking on it.
Would it be worth using ss box in a lattice with a thin skin to support the tiling? Even if a bit heavier it minimises he said/she said if there are issues
If you go with glass have you means to illuminate the pit? The glass will look more interesting when back lit.
if you are concerned about strength there is always carbon fibre, https://www.easycomposites.co.uk/hig...on-fibre-sheet
We have a ‘hidden’ manhole in our resin driveway, stainless structure with access when required, covered with the same resin as the drive, so you only see the edge of the frame.
Originally designed to be a cover for a floor in a factory / warehouse apparently. To access it, I remove the screws & screw in the handles.
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In my workplace we have some suites with a very high fit & finish standard.
A company called ACO make 'Solid Covers' that sound like what you are after.
Very similar to what we have, but ours have less visible metal. OP can ask the fitters if interested regarding the brand.Originally Posted by TimeThoughts
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