Soloution required pls

[nelly05]

Cheers for looking.

I have in my back garden a manhole - its the made of the precast retangular section 1000x650 (approx).

Whilst having the garden dug out the digger managed to destroy the reducer slab / buscuit on top of it.

Now this needs replacing and its not cheap. I am struggling to find one the right size anyways and they come as a frame and cover - which due to me using a recessed m/h cover eventually i dont need the cover.

Anyway i am trying to come up with another soloution - any ideas.

I have toyed with the idea of using a 3x2 slab and corbelling the sides to make a base for the recessed m/h cover, but was unsure as the 3x2 are not reinforced.

Other option a 600x600 6mm steel plate, cast concrete plinth on top with mesh in and then build off this for the recessed cover.

Need to sort something as levelling the area had ground to a halt. It will have mot on top the indian stone so only ever light weight traffic.

TIA

Regards

[flowjoe]

nelly

If it just taking foot traffic use a 3x2 slab and bridge the un-supported side of the flag using angle iron, which would obviousley overlap either side of the chamber. Dependant on depth you can double up the slabs or flood over with concrete.

Hope that make sense, if not i will try to provide a sketch.

[seanandruby]

if you are any good at shuttering you could erect a timber deck using rips of ply. then box out 600x600 for the opening. add reinforcing with spacers to lift the steel off the deck, then concrete it in situ. allow 40ml cover all round concrete.

[flowjoe]

I just took another look you O.P

If the slab is going to be taking vehicular traffic sean if right, you will need a reinforced slab of some description whether that be cast on site or prefab, or you are looking at steel plates which aint too cheap.

[nelly05]

Cheers for the replies.

It is only for foot traffic, the slab itself will be buried under not and indian sandstone, with spare blocks used to lift the recessed manhole cover to the correct level.

I think i will use a mix of the 3x2 slabs and arrange to suit. Was just worried that it would need to be reinforced.

Cheers

[seanandruby]

a span of 1000x 650 is a big span to be covering with heavy,infill etc. i would opt for reinforcing and a wet cast slab every time, or, try a reclaimed building materials yard.

[nelly05]

I could do that i suppose, when you say rib you meanput small strips underneath the main piece of timber?

you recommend casting insitu and leaving the ply in place or casting to one side and moving into place after.

i guess would need to be 90 thick then - 40 cover x 2 plus 10mm bars!!

Causing me a massive headache this - cant do anything till its done and i need to find somewhere to buy reinforcement local to me.

Regards

[IanMelb]

need to find somewhere to buy reinforcement local to me.

Travis Perkins ?

[seanandruby]

Depends how deep the manhole is. you will have to erect two sole plates, one on either side lengthways.That is an upright on either corner with two lengths of 4x2 on edge, or 6x3 spanning two legs each ( those are your primaries ) cut three pieces ( secondaries ) and place them width-ways. next cut some "rips of ply" and place on top of the cross members ( we use rips which are offcuts of timber for ease of striking decking.) you have to work it out so that the ply finishes level with top of manhole. now make a box 600x600 to finish about 100ml below the finished paving level, if you have the depth allow for a minimum of two, or maximum of four course of engineering bricks. Next place the steel allowing about 40ml cover all round. mix the concrete about 50 slump C40. hope this helps? good luck.

[nelly05]

Manhole is not very deep m8, only about 500. Its a private manhole that leads off into another nahole joined to main sewer.

The original cover was only about 60 thk, with what looks like 6mm thick bar in it.

was thinking of casting it to one side, approx 80 thk with layer of mesh in the middle.

When completed there will be approx 120 on top which is the depth of the recessed manhole.

In reality i could cover it over with steel and forget but you can guarantee at some point i will need to look inside it.

Am really confused now as to best option.

Regards

[nelly05]

Spoke to a guy in the precast yard local to a site i was on, he suggested to me:-

sheet of ply laid out on a level pallet.

fix shuttering to sheet of ply to size required.

pour 75mm thick overall, made up of 25mm, then a sheet of mesh, another 25mm then another sheet of mesh then 25 cover to finish.

Suggested a mix of 1:2:3 or 1:3:4 which is approx c20.

stick some bent rebar in to use as lifting handles.

Seemed to think that should do the job.

Then place into position once its gone off enough to luift (suggested 2 days would be sufficient to backfill over)

Was a helpful fella, gave me some spacers and two small sheets of mesh offcut.

Sound ok?

Regards

[seanandruby]

thats ok, but will be heavy to manhandle. did you put the "bent rebar" under the mat first otherwise the handles will fly out, especially if you lift it with a machine. the way i described is ideal if you need to push the job on because you can strike it at a later date, also has longer to cure. ive just had to strike 50 of same, wider and deeper tho.