A masonry question.

[Dave Plowman (News)]

I have a London Victorian semi - built out of London stocks and what appears to be 'stone' for lintels pillars and mouldings etc.

The party wall sticks out above the roof by about 9" or so and was capped with the same looking stone originally - but this was replaced with I assume concrete ones when the roof was replaced some 20 years ago.

At the front of the house, ie the end of this party wall, instead of bricks and a capping stone, there appears to be a one piece block the width of the wall, 3 courses high, and going back about 9" with a horizontal capping as part of it. It may also include a short section of capping at 45 degrees - difficult to tell from the ground.

It's breaking up - quite large chunks were found on the path the other day.

I'd like to make up a new one similar to the original. My idea is to make up a suitable mould out of MDF etc and cast a new one in the workshop. Unless someone already makes such a thing?

Any tips? Like what mix of concrete to use, etc?

[nicknoxx]

In true 'not what you asked' fashion, I'd be inclined to replace it with stone. Bath stone is very easy to work, you can cut it with a hard point wood saw and if there's no complicated corners mouldings it should be a really easy job. Satisfying too.

[stuart noble]

I've made similar things using a 1:6 (by volume) cement/vermiculite mix (Perlite will do instead). Obviously much lighter, but IIRC it took longer to dry than normal mortar. Not that different to a breeze block actually, but I needed custom shapes.

[js.b1]

Stone as mentioned, it is not just thermalite which cuts easily.

If you want to go the concrete face - for a smooth face use a different mix against the shuttering, then a conventional mix in the middle if you see what I mean. Plus a lot of tamping to get the air out etc.

[Dave Plowman (News)]

Interesting. But since the block is basically T shaped in section there'd be quite a bit of stone to remove. I've also no idea where to buy such a thing - or want to spend too much. The existing one is painted.

[Dave Plowman (News)]

Yes- I'd guessed that.

Doesn't look to be huge from the ground - going by the bricks.

The parapet capping was replaced quite recently so I'd guess is well cemented in place.

Luckily they have more money than me. ;-)

Thanks for the info. My thoughts were a scaffold tower would reach it ok.

[nicknoxx]

[1501]

If you're going for the cast concrete approach you might want to consider casting it in-situ.

[cynic]

=A0 London SW

Speak to Belzona Molecular Co. for repair compounds, but be prepared for some steep prices

[fred]

In article , Dave Plowman (News) writes

There's a lot of force working on them when they're on a slope and they're frequently pinned (meaning 10mm stainless) to avoid them slipping, even with the key block in place.

This case was on a bigger scale being a tenement but it shows what can go wrong:

[Dave Plowman (News)]

Not knowing anything about this sort of stone, would the damage likely be confined to the outside bits - ie the core could be ok? If so some form of repair might be easier than replacement.

Ages ago I bought a Belzona repair kit for a Rover ally engine - to fix the block where it had eroded due to a gasket failure. Was a Rover part - and expensive, but worked well. Would that be the same company?

[Dave Plowman (News)]

Finally found the pic. That's a very different design to mine, which is supported by the party and front wall - ie no overhang. The face of it is flush with the front wall.

Looks something like this:- Front _______________ |__ ___| | | | | |_________| Side /\ __ _______________/ / | |_________________/ | | | | | |___________________|

Not, of course to scale, but it's the rough idea.

[stuart noble]

Maybe body filler then. Can't see much point in buying expensive products for a basic resin repair. I've used the bog standard stuff from car paint suppliers to repair the corners/edges of stone sills and it's been rock solid for donkeys years. Bondaglass are over in Beckenham if you want something more specific. Very helpful and knowledgeable IME.

[Martin Pentreath]

=A0 London SW

Just to complicate things a bit more, this is probably the sort of thing that ought to go through the Party Wall Act process:

[Dave Plowman (News)]

There's no way I'd do anything without consulting my neighbour. He'd be paying at least half. ;-)

[Dave Liquorice]

IIRC you said the front is 3 courses high and on a 9" wall, is the proportion height/width more or less the same for the length? Thus making the block approximately 9" wide, 12" high and 18" long?

If so that is going to be a hefty lump of stone if you come to remove and replace it. I've got some stone window cills here 4" thick 10" deep and 48" long (1920 cu ") they are almost super glued to the ground. If your block is 9 x 12 x 18 that's a similar volume...