Cleaning sandstone

[Feltwell]

I'm having to re-build our gate piers, as both are leaning by an increasing amount each year.

The stone blocks halfway up each pier are, not to put too fine a point on it, "mullered". Half of what should be stone is cement mortar - the original cast-iron gate fittings put into the blocks have rusted and blown the blocks apart.

So new ones have been ordered in a stone from a local quarry which should, after a good few years of weathering, look the same as the originals.

The question is - the pier caps, which are OK to re-use, are stained green from where they sit under the trees:-

To clean or not to clean? Opinions? Bear in mind they will be sat above shiny new blocks of stone.

And if to clean, how? I had a brief go at one section with a scrubbing brush and plain water, it did very little!

 

[Flyfisher]

I'm not sure I'd bother with much more than a good scrub with a soft brush either. Besides, unless you remove the offending trees (which I'm not suggesting!) then the "problem" will return - the quotes are to denote the fact that I personally don't see the discolouration as a problem, just natural weathering.

On a related matter, brick gateposts seem to prone to subsiding, unless I only notice the non-vertical ones. I presume it's mainly due to a tall, thin but very heavy mass being built on insubstantial foundations. And hanging gates can't really help things. On the few occasions I've seen new brick gate-posts being built, they've been built around an RSJ, which presumably was bashed a fair way into the ground.

 

[JoceAndChris]

I'd want them clean, but I know it's a matter of taste.

When in our last flat we had a pretty rubbish pressure washer for cleaning the outside patio, it wasn't particularly powerful but all that green got shifted off. I guess you'd have to be very careful with sandstone.

House and garage look fab, BTW!

 

[Feltwell]

On a related matter, brick gateposts seem to prone to subsiding, unless I only notice the non-vertical ones. I presume it's mainly due to a tall, thin but very heavy mass being built on insubstantial foundations. And hanging gates can't really help things. On the few occasions I've seen new brick gate-posts being built, they've been built around an RSJ, which presumably was bashed a fair way into the ground.

It is a concern. The left hand one should be OK as I will be tying it back into the wall. The right hand one, with all the wall behind it, is being pushed over by a neighbour's beech tree. I'm just going to re-build them on existing footings - it's taken at least 50 years for it to get to this point (I have an aerial picture from 1950's showing the offending tree) and I reckon that even if I put new footings in the same thing will happen. At least they are both tied into a fairly substantial 9" wall, and not just free-standing.

I will be putting double gates in though, which should put less load on each post.

 

[Feltwell]

House and garage look fab, BTW!

Thank you! Basic structure of the garage is up, but it still needs lots of finishing work & all the joinery (I won't get the doors until mid-Jan at the earliest). When I get round to it I'll post an update on the original thread.

 

[JoceAndChris]

Oooh well done. Looks like a massive job, with a great end result though! Fancy coming and smashing up my huge breezeblock and concrete monstrosity and replacing with that? No, didn't think so - sounds like you've got quite enough to keep you occupied!

 

[Moo]

To clean or not to clean? Opinions? Bear in mind they will be sat above shiny new blocks of stone.

You will need: a bucket half-full of water; a scrubbing brush; a large paintbrush.

Stage 1: Dip the scrubbing brush in the water and scrub the green stone. Repeat frequently. The water in the bucket will go more and more green, while the stone will become less green.
Stage 2: Dip the paintbrush in the green water and paint the new stone blocks. Repeat frequently until the new stone matches the old stone.

 

[MdB]

During our renovations, part of our sandstone wall had the gutter empty onto it for a while (too long to be honest) and the stones turned green. Once we fixed the downpipe for the gutter properly, the stone lost its greenness (thankfully) as I guess the sunlight and lack of extra moisture caused it to dry out and stopped it from being a suitable home for the algae.

It may be worth putting the stone caps undercover (so as to keep fairly dry) but in the sunlight and see what happens.

I would also guess that the algae is well below the surface so scrubbing and the like will have little effect.

 

[Feltwell]

Moo & MdB, thanks for the thoughts, very interesting. I think a combination approach might work - scrub them (which from limited go so far does very little to the stone, but does turn the water green) and then use Moo's idea to paint the water on the new stones. Won't do much to the exisiting stones but may help tone the new ones down a bit.

 

[Penners]

I reckon Moo's idea is brilliant. Clean up the old masonry - a bit, and dirty down the new masonry - a bit.

A compromise worthy of Soloman himself.

 

[Carol]

I have been told to paint my new bits of stone with yogurt to encourage the mould growth so it matches the rest. I think Moo's idea sounds much less smelly!

 

[JohnB]

I have been told to paint my new bits of stone with yogurt to encourage the mould growth so it matches the rest. I think Moo's idea sounds much less smelly!

If I tried that my dog would lick off all the yoghurt :lol:

 

[Feltwell]

Well, the quarry called this afternoon to say my new stone blocks are ready, so we shall see what difference 110 years makes to a piece of sandstone!

I'm glad the pier caps are useable again though - even just 2 plain stone blocks aren't exactly what you'd call cheap.

 

[Tom]

Bear in mind they will be sat above shiny new blocks of stone

Don't worry. The new corner stones and lintels we put in earlier this year are already difficult to pick out from the originals...and we did nothing to them

 

[Penners]

I have been told to paint my new bits of stone with yogurt to encourage the mould growth so it matches the rest. I think Moo's idea sounds much less smelly!

A dilute wash of cow sh... er, dung, will have the same effect.

 

[Feltwell]

Chatting to the stonemason at the quarry today, he recommended diluted cow dung as well! But that's more I believe to encourage mosses and lichens.

Jaqy, your reply is very encouraging! The quarry have said the stone will change colour fairly quickly - I also believe that it's supposed to get stronger as it weathers, currently the stone is very soft and easily chipped.

I think I'll try Moo's idea of paintingthe new stone with the water from cleaning the old, and see how they settle in. If they still look bright and new in a year's time then I might try the cow poo trick!

I am now going to go and do myself an injury getting the blocks out of the car - by 'eck they're heavy!

 

[Jon Maine]

I have been told to paint my new bits of stone with yogurt to encourage the mould growth so it matches the rest. I think Moo's idea sounds much less smelly!

A dilute wash of cow sh... er, dung, will have the same effect.

Organic matter, we found a 4 pint of milk which had been forgotten on a building site over a weekend in the mess hut, left it a few more days until it became a semi solid, painted it on new stonework and 3 months later was as green as everything else.

 

[Feltwell]

Got my new sandstone blocks - Can you tell that they're new compared to the pier caps???? :lol:

Will post up more pics when all is completed.

 

[chuckey]

Its a bit late now, but. . . I rebuilt a pair of pillars with an arch in between them that were leaning about 6" out of true (outwards towards the pavement). The big problem was that one of the pillars was the end support for a 7' high panelled wall which the leaning pillar had pulled over with it. So my problem was that I would have had to rebuild this wall panel (about 15' long) as well as the pillars/arch. I choose to "break" the wall diagonaly between the bottom of soon to be rebuilt pillar and the top of the next wall pillar. This I did by chiselling out the mortar in the correct courses, strapping some 4" X 2" to it at stategic locations and giving it a mighty pull. It was realigned to get the wall "upright" at the new pillar end and the resulting mortar courses were then deeply re-pointed - the whole wall was going to be re-pointed (130' long!!) anyway. The arch and pillars were thern rebuilt. Its been there 20 years and still looks OK.
What I was going to say about your pillars, their foundations are weak, but their relative movement will be slow. So select a mortar course really low down and on the side that requires lifting, chisel out the mortar as deep as possible. Stuff two bits of hardboard in the gap and using bolster chisels and wedges gently, you should be able to lift the front of the pillar up. Could be an idea to remove the gate to lighten the load and strap some 4" X 2" on the back of the pillars to generaly hold things in place. I reckon you can get the pillar to assume a vertical posture. Then dig out and re-point your butchered mortar course to hold it in place. The mortar course will be depth of pillar/height of pillar X "out of plumbness", at a guess, H = 4', D = 18" P = 2", so added thickness of mortar = 1.5/4 X 2 inches ~ 3/4". Not very neat but you could do both sides in a morning.
Frank

 

[Feltwell]

It's all down now Frank, but it needed that anyway.

One side was attached to a wall which was starting to get too much lean for comfort, there wasn't much you could do with it apart from rebuild it. A partial rebuild and repoint the rest may have been an option - but on speaking to the bricklayers, they said it was hardly worth it and it would take just as long as rebuilding the lot. Given how much they've got done today, I reckon they're right.

The other pier was attached to a wall which had failed further along, the whole end section was falling away from the rest. In both piers the stone blocks had gone.

I could have gone for a "patch it up" option, but in view of all the other work we're doing it seemed better to just get it done properly. Hopefully by the time it needs doing again, it will be someone else's problem!