Restoring deteriorated sandstone

[Feltwell]

Hello,

Well, on this glorious bank holiday weekend, I'm finally getting around to renovating the entrance porch to Feltwell Towers, a long long overdue job.

Alas the first discovery is whilst the leadwork I did about 3 years ago has done it's job - roof structure and brickwork are bone dry - the damage was already done, 2 of the joists are totally shot and the flat roof decking has rotted at the outside edge. So it's a complete new roof job It is at least only about 4' square, and when done (in lead) it will be the last bit of felt banished from this house.

Anyway - part of the overall refurb is to try and improve the appearance of the stonework, which I'm pretty sure is sandstone. I've got a lintel over an adjacent window which some troglodyte drilled fixings into, so of course it's cracked:-



Plus the main stonework above the doorway has a very crumbly surface, it's in a state, and it's also cracked - plus the cheap horrible outside light that was fixed to it, with a surface mounted cable, the eejit carved a groove in the stone to get the cable under his cheap B&Q light :evil: :evil: :evil:





Anyone got any experience of stone repair? it's a new one to me. I know the crack repairs would be cosmetic only, that's fine, the stone is well locked in. Currently thinking of 2 options:-

DIY - This firm https://www.lime-mortars.co.uk/stone-repair/stone-consolidant do a consolidating product for crumbly stone - alarm bells would normally ring but the rest of their products do look to be generally old house friendly, and I do think the surface needs consolidating. Not sure how invisible I can make a mortar repair look, as I've no experience.

Chicken out - as it's a very prominent part of the house, get a professional in, in the hope they can do a better repair. This firm is quite local, and has certainly worked on some prestigious projects https://midlandmasonry.co.uk/stonemasons/

Anyone got any experience of sandstone repair?

 

[plasticpigeon]

My experience is that lime falls out, and cement is generally rather hard bit can at least stick. Perhaps a weak cement lime mix would work. 1:1:6 is a bit harder than stone, so maybe 1;1:8 or 1:2:8 or something. I reckon white cement and soft sand the right colour to blend in well. I think it is probably one for trial and error. There is a product called lithomex that is suposed to be lime based and in the right hands the results look very fine, but I have no first hand experience of it.

https://heritagestonemasonedinburgh.com/lime-mortar-works/lithomex-limemortar-repairs/

 

[Flyfisher]

What about the ‘partial’ chicken out option, ie asking the professional stonemasons for their advice before DIY? I’m guessing you don’t really want to ever revisit this repair so the trial and error approach might not appeal (it wouldn’t to me!).

My concern would be about the structural integrity of any repair. I’m guessing that a cosmetic repair of the drilled hole and the cracks would be relatively easy but that it would do little or nothing to restore the strength of the stone. You say it’s solid but drilling the hole itself surely wouldn’t have caused those cracks directly, they would (I’m thinking) be a result of the stone being weakened and structural forces then causing the cracks. Ok, so the stone may have moved into a now stable configuration, so structural strength might not be an issue (told you I was guessing :wink: ).

If structural strength is important, how about using some sort of chemical fixing injected into the hole, which would likely seep out into the cracks as well, but keeping the outer half inch or so clear to allow space for a purely cosmetic surface repair?

 

[Feltwell]

We had a full structural survey done here when we bought the place, the cracks were all present then. The surveyor wasn't concerned - he said the stones were locked in and would still offer support, the cracks looked like they had been there for many years and there was no sign of any distress in the masonry above. It looks like it was expanding fixings for a downpipe that a previous owner tried to fit that caused the problem :roll:

The firm that sells the consolidation product are stonemasons and say they offer advice, so I've sent them a mail. That's the only problem with DIY & specialist jobs - by the time you've established what you're doing and got half decent at it, the job is over!

I suppose worst worst case is the front inch or so of stone is hacked off, for new sawn pieces to be mortared on to the front - there is a quarry I used for cut stone for hinge blocks for our gate pillars who could supply the "tiles" of new stone I'm sure. Not what I want do though, new stone would stand out and I would far rather make the best of what is already there anyway. Lithomex is another option, the link from PP shows some impressive looking repairs.

 

[dandrew]

I had a similar problem to you, though functional rather than aesthetic, and one of the 'trades' that I got to look at the job also recommended Lithomex. I'd never heard of it before so called the SPAB technical helpline, which at the time offered a free information service for a few hours a week and you actually spoke to a person who knew what they were talking about. The upshot of the discussions were that plastic repairs were considered to be temporary (regardless of whatever material you used to make the repairs, and they wanted the data sheet before reaching an opinion on the actual product) rather than permanent, and a life span of 5-10 years was though to represent good performance. On hearing this I decided to get a 'proper' repair done, which involved carving, scaffold and the whole nine yards. Your issues sound less structural and more appearances-based, so you could use the Lithomex as an experiment and it it works then great.

David

 

[Feltwell]

Thanks, that's useful. A 5 to 10 year life span sounds very poor to me - 50 to 100 sounds more like it!

I am wondering if I can simply use a consolidation chemical to toughen up the outer surface of the stone and stop the disintegration, then rework it with a chisel to give a cleaner face - with some repair mortar filling of the cracks. Yes, I'd end up with a stone face a few mm back compared to how it was built, but that isn't really a problem.

Let's see what a couple of professionals think - my local stonemasons, and the suppliers of repair materials that I've quoted above.

 

[88v8]

Had some work done by a local mason recently, was surprised how easily and accurately they were able to cut out pieces and replace them using a small disc cutter and an air chisel.

You've probably seen this article
http://www.buildingconservation.com/articles/sandstone-conservation/sandstone-conservation.htm

There is also a Telegraph article - Property clinic; how to repair weathered sandstone might be some use but the page won't load for me.

In Cyprus we saw some fantastically eroded sandstone in an old tower. Holes so big there were pigeons nesting in them. Nature in action.

Other than the cracks which could be repaired with one of those two-part resins in a cartridge, I suspect that you either need to do some replacing or give it a good ignoring. New stone can be aged by spraying it with sour milk.

Ivor

 

[Feltwell]

Well, an encouraging response from the master stonemason at the company that sells the consolidant chemical - he says from my pictures it's not needed, the stone needs descaling and redressing. As for the cracks, remove the rusted fixings (easier said than done I suspect) before filling with a colour matched stone repair mortar (which they can supply).

A helpful reply and not pushing their products on me, I like companies like that!

 

[Feltwell]

Well, some interesting points (to me at least!) from the masonry contractor who called today:-

- Cracks should really be stitched by cross drilling at an angle across them, and inserting stainless steel bars with resin to ensure stability - which makes sense
- Old metal fixings that have rusted & caused the cracks have to come out to stop future problems as they continue to rust - even though digging them out will do more damage -suggest drilling carefully around them
- Deteriorated face on the stone above the door caused by damp - makes sense, I know that area has been very damp in the past, and the stone there is far worse than anywhere else on the house. Damp penetrating from above has carried salts to the face of the stone (you can see them) and caused frost damage to the face
- Face can be ground back with a diamond disc but it will look like new stone, as well as recessing it. Suggested rubbing down by hand first with a carbide abrasive block to see what I think of the finish - can always go over with a disc afterwards - which makes sense. I've ordered a couple of rubbing blocks to give it a go.
- Filling can be done with a cementitious mortar mixed with stone dust for a colour match - which I'm a little uneasy with, the supplier of stone repair material I found did a lime based repair mortar. Cement may well stick better, so long as it doesn't trap moisture behind it.

So it's given me some ideas. Not sure if I'll go with them or have a go myself, not had a price yet for one thing! Stitching the cracks I presume could be done with a Helifix kit, even though it's not strictly what they are intended for - unless anyone has any better ideas. It's shear strength I need here, stop the 2 faces of the stone moving relative to each other. A helifix kit on it's own isn't cheap, £200 in Screwfix!

 

[masochists-r-us]

We used lime based mortar, mixed with stone dust for colour match to repair 4 ironstone jambs on two inglenook fireplaces. The vandal who lived here before us had smashed them to key in modern brick walls which we have since removed. Most people are completely unaware that they have been restored. The colour match is practically perfect, but unlike the untouched and characterful originals, they have a more perfect looking surface, shall we say. I suppose we could have bashed them with a nailed stick for authenticity though ... maybe one day when we've nothing else to do !

 

[Feltwell]

That's good to know, thank you.

Had a quote through today - £285 + VAT for a mason and his materials for a day, which will cover the work. Bargain - a helifix kit that I'd need to buy would cost £200 on it's own. Well it's a bargain if he does a good job! From a reputable firm though, I know some the contracts they've worked on round here.

 

[plasticpigeon]

Yes, if the mason is skillful that sounds a great price. However your £200 helifix price can be bettered. I bought a length of the stainless helifix wire for about £30 and the tubes of 2 part anchorfix construction resin are less than a tenner each. If you want some stitching wire and if I can find it I can send you some or you can pick it up if you are passing Brum as I know you are not far away!

 

[steveb]

We used a good stonemason down in Devon - came out at £420 for 2 days work - he managed to take second hand granite kitchen worktops and "adjust" them to fit our layout, looks like it was designed to be there in the first place.

All cut by hand with an angle grinder - money absolutely well spent

 

[Feltwell]

Thanks everyone - and PP, that's a very generous offer. I think I'll go with getting a Mason in though, it's a very visible part of the house so I'd like the best possible job, and it's not that expensive, in the grand scheme of what this place costs me!

The Helifix did seem expensive, that was the kit that Screwfix sell - in fact it's got even more expensive, £210 now. A lot more bar than I need as well.

https://www.screwfix.com/p/helifix-crack-stitching-kit-grout-300mm-x-1-04m/34894

 

[plasticpigeon]

Just in case.

 

[Feltwell]

Stonemason rang up last night, "Been delayed on another job, can I come tomorrow?" - Yes!

Here now and I have to say he's doing a great job. So nice when you get someone in who not only is very good at his trade but takes as much care over your house as you do. Pictures to follow!

Such a good job is being done that I'm thinking of getting them back to repoint the brickwork on the house - a job that needs doing that I, whilst capable of doing it myself, am quite frankly never going to get enough time to do.

It can't be just me who finds getting a tradesperson (being pc!) in much more stressful than just doing the job myself?

 

[steveb]

It can't be just me who finds getting a tradesperson (being pc!) in much more stressful than just doing the job myself?

I only find that if getting the wrong tradesperson in.

 

[Feltwell]

The Before:-





And the After - A big improvement I think - all still a bit dusty and needs a year or two to dirty up a bit, but.....



Big crack here reinforced with a stainless rod drilled through, filled back, nearly invisible now. Stone had to be refaced as it was in such a state.





I didn't post a photo of the step before, it was in a right state, all chipped round the edges and covered in some dreadful old floor paint that had worn through patchily. Now pointed up back to the house (big gap before) plus a large crack filled.



Honest repair above this window - old iron fixings that caused the crack dug out, stainless rod drilled through from underneath to stabilise it. Only way to blend it in would have been to reface all the stone, didn't really want do that here.

Before:-



And After:-



Again, honest repair to crack in middle of lintel - and again reinforced with stainless allthread bar drilled across the crack from below and epoxyed into place.



Now I've just got to finish renovating the rest of the porch. Stonework at the very top, almost out of shot surrounding the flat roof, is going to get covered with lead, I need to make sure the damp is kept out for good - it was far worse than I thought when I started stripping the roof back. It's the damp penetrating from above that made the stone lintel above the door go so bad.

 

[Craig89]

Some "cracking" repair work done there

 

[overlander matt]

We have stone window sills around our house and intend to put in a couple of new sash windows which should hopefully match the originals. The CO has specified stone sills (approximately 1m wide) which suggests we need to have these made for us bespoke. Does anyone have any experience getting new stone sills and the approximate cost?

Thanks,

Matt