Cracked manhole cover and paving lifting up
 

Hello,

I have two problems related to a sewer manhole.

The first is relatively easy. The manhole cover is cast iron, really
heavy, has lost its little lifting bars / rods that used to lie on top
of semi-circular "recesses". The manhole cover has cracked and is
really, really difficult to lift using an old screwdriver that keeps on
slipping out from the "lip" of the cover. For all these reasons I want
to replace the cover. The cover is in a small, paved front garden and
nothing heavier than a full dustbin passes over it. Can I replace the
cast iron cover with a galvanised steel one?

The second problem is related to the first. All of the front garden
is paved with some incredibly horrible slabs. I remember when a couple
of slabs were lifted years ago that they are laid on tarmac - don't ask
me why. The slabs have been down for at least 30 years. The problem is
the slabs around the manhole have "heaved". Think of the edges of the
slabs next to the manhole have all been "lifted" so that water on them
would run away from the sewer manhole. Now the slabs are not moving at
all when you stand on them, they feel completely secure. I lifted the
manhole cover (with difficulty, see above). I inspected the brick
lining of the "sewer access". There the bricks seem all intact and that
nothing seems to have moved. However, the bricks just below the manhole
cover "frame" are of a different type to those lining the "sewer access
pit". The mortar is very rough and bits of slate acting as "shims" are
in there too. I am guessing that when the paving slabs were laid the
whole level of the front garden was lifted so the manhole cover frame
had to be lifted too and it was just bodged up when it was relaid. Now
..... I can't see any reason from inspecting the lining of the "sewer
pit" why this "heave" is happening. Hence, when I replace the manhole
cover and the slabs what is the possibility this "heave" will happen
again?

Thanks

Clive

Cracked manhole cover and paving lifting up
 

In article . com,
"Clive" writes:
Hello,

I have two problems related to a sewer manhole.

The first is relatively easy. The manhole cover is cast iron, really
heavy, has lost its little lifting bars / rods that used to lie on top
of semi-circular "recesses". The manhole cover has cracked and is
really, really difficult to lift using an old screwdriver that keeps on
slipping out from the "lip" of the cover. For all these reasons I want
to replace the cover. The cover is in a small, paved front garden and
nothing heavier than a full dustbin passes over it. Can I replace the
cast iron cover with a galvanised steel one?

Probably, but they're terrible. I bought one to set into
the path up the side of the house which only has pedestrian
traffic. When you stand on it, it flexes and goes "ping, poing".
Took it back and got a cast iron one, which was only a little
bit more expensive. IIRC, the galvanised one was 3 tonnes load,
and the cast iron one was the lightest duty cast iron (10 tonnes
load?). You may need to buy some lifting handles too. A good
builders merchant will have all the bits.

The second problem is related to the first. All of the front garden
is paved with some incredibly horrible slabs. I remember when a couple
of slabs were lifted years ago that they are laid on tarmac - don't ask
me why. The slabs have been down for at least 30 years. The problem is
the slabs around the manhole have "heaved". Think of the edges of the
slabs next to the manhole have all been "lifted" so that water on them
would run away from the sewer manhole. Now the slabs are not moving at
all when you stand on them, they feel completely secure. I lifted the
manhole cover (with difficulty, see above). I inspected the brick
lining of the "sewer access". There the bricks seem all intact and that
nothing seems to have moved. However, the bricks just below the manhole
cover "frame" are of a different type to those lining the "sewer access
pit". The mortar is very rough and bits of slate acting as "shims" are
in there too. I am guessing that when the paving slabs were laid the
whole level of the front garden was lifted so the manhole cover frame
had to be lifted too and it was just bodged up when it was relaid. Now
.... I can't see any reason from inspecting the lining of the "sewer
pit" why this "heave" is happening. Hence, when I replace the manhole
cover and the slabs what is the possibility this "heave" will happen
again?

I suspect the manhole top is where it always was, but the ground
around it has sunk. Perhaps it hadn't had cars driven on it much
before?

I suggest you remove the top packing pieces, and if necessary the
top row of bricks. You might be able to get the slabs to lay flat.
Lay a thick mortar bed around the top, so the frame is slightly
proud when positioned on top. Using a piece of straight timber
laying across the frame, tap it down until it's flush with the
surrounding ground. Check in both directions. (The cover is
normally flush with the top edge of the frame, but you might
want to check that before fitting it in this way.) When it's in
position and started to set a bit, you can mix up some more to
'grout' in to the edges of the slabs.

When working on a manhole, I cut a piece of ply to fit quite
closely across the bottom, resting on the flaunching. This catches
rubble, mortar, etc, rather than it going down the sewer. Also
enables you to rescue the odd dropped tool without having to wash
the sh!t off it, or watch it vanish down the sewer ;-0
Sometimes it's useful to stand on too.

--
Andrew Gabriel

Cracked manhole cover and paving lifting up
 

Clive wrote:
Hello,

I have two problems related to a sewer manhole.

The first is relatively easy. The manhole cover is cast iron, really
heavy, has lost its little lifting bars / rods that used to lie on top
of semi-circular "recesses". The manhole cover has cracked and is
really, really difficult to lift using an old screwdriver that keeps
on slipping out from the "lip" of the cover. For all these reasons I
want to replace the cover. The cover is in a small, paved front
garden and nothing heavier than a full dustbin passes over it. Can I
replace the cast iron cover with a galvanised steel one?


You can use plastic if you can get one to fit, although galvanised is
cheaper.

The second problem is related to the first. All of the front garden
is paved with some incredibly horrible slabs. I remember when a couple
of slabs were lifted years ago that they are laid on tarmac - don't
ask me why. The slabs have been down for at least 30 years. The
problem is the slabs around the manhole have "heaved". Think of the
edges of the slabs next to the manhole have all been "lifted" so that
water on them would run away from the sewer manhole. Now the slabs
are not moving at all when you stand on them, they feel completely
secure. I lifted the manhole cover (with difficulty, see above). I
inspected the brick lining of the "sewer access". There the bricks
seem all intact and that nothing seems to have moved. However, the
bricks just below the manhole cover "frame" are of a different type
to those lining the "sewer access pit". The mortar is very rough and
bits of slate acting as "shims" are in there too. I am guessing that
when the paving slabs were laid the whole level of the front garden
was lifted so the manhole cover frame had to be lifted too and it was
just bodged up when it was relaid. Now .... I can't see any reason
from inspecting the lining of the "sewer pit" why this "heave" is
happening. Hence, when I replace the manhole cover and the slabs what
is the possibility this "heave" will happen again?

It's highly likely that the area around the manhole has been dug out to a
decent depth (to relay the upper courses of brick) and filled in with
hardcore or even concrete....when the rest of the garden has settled, this
part has not.