Practically Classics Forum

Hi Chaps,
Got a question for the builders / house restorers among you completely off topic I know but at least the house is a "classic"

Sorry, this is going to be long winded,

My old house is a single story "cottage" built about 200 years ago, with solid stone walls, the walls are of the local flagstone laid quite roughly one slab atop another and varying in thickness tremendously from about an 1/2 inch to 5 inches thick. The walls are a good 2 foot plus deep and were originally built with lime mortar and left bare. The stone while similar to sand stone is very dense and hard.

The house was "modernised" in the 70's and then a harled finish (pebbledash) chucked up to cover all the sins. Then re dashed about ten years ago, but inspection shows that to have been thrown over the existing dash.

So, following this winter I have a couple of walls with large hollow spots behind the rendering and some spalling, in effect the entire coating needs to come off and be redone on these walls.

Ideally I'd be looking at a lime render or simply removal of dash and then pointing as more sympathetic but....

1.. I've never lime rendered,

2.. I cant do a pointing job as there turns out to be some unsightly concrete blocks making good the odd area at the roof line and given very tight mortar joints it would have to go on and be a brush finish anyway.

3.. Cost is going to be an issue, a very big one as we may one day have to consider selling up and houses are worth very little up here.

So, I have worked with brickies in the past and rendered with Sand and cement, so it will probably have to be this method, unsympathetic as it is. What I need is the best mix possible given the construction, I'm thinking Sharp Sand and Builders sand with cement and a little lime thrown in for good measure.

Can any of you advise the best ratios, for scratch coat and then finish coat, I know we have to get weaker as we go,

And a question that nags me, Why do we always use two coats, why can I not simply throw one coat about ten to 15 mm thick following the shape of the wall and stones for a rough rustic finish which could then be painted more in keeping with the style of finish of the old lime renders and limewash / whitewash effect that were once common on rubble built houses. I considered the monocouche type renders as seem to be popular elsewhere but I think cost will be prohibitive.

Thanks Chaps, all advice appreciated.

Have you tried WD 40?

Well if nowt else that cheered me up

Hi Mr. Eye - I live in a large 15th century house and am in the process of doing a total renovation, entirely using traditional methods and materials. I've been at it for nearly 6 years now so I have quite a lot of experience of doing this sort of thing.

My comments would be that the reason the dash has broken up and spalled is that modern cement-based materials are completely incompatible with the traditional structure of the walls and the rigidity of the cement allied to its inability to breathe properly will a) damage the underlying structure in the long term and b) not last long in the short term, as you have found.

I'd strongly recommend just rendering it with Lime Mortar. Before you react to this, trust me, it's easy, much easier than cement or plastering, and MUCH easier than pebbledashing.

There's a lot of "fright talk" about using lime, and if you're going to make your own lime in a kiln etc. then that would be the case - it's scary and very time consuming. However, the best method is to use pre-mixed lime mortar in 20kg tubs (or you can buy larger quantities).

This is what I do. Naturally, lime mortar hardens in the presence of air, which can take many months (or years) to properly "go off", whereas cement is a hydraulic mortar, i.e. it goes hard in the presence of water. So, you can turn your lime mortar into a hydraulic mortar by adding what is called a Pozzolan, I use a brand called Argical. It's a fine flour-like powder, which you add in a ratio about 8:1 and it acts as a catalyst, so the mortar will start to go hard well within a day - slower than cement, but not much.

I buy my lime stuff from Mike Wye - it's not that expensive, the delivery charges cost mroe than the product!

Here:
http://www.mikewye.co.uk/product-catego ... -products/

Give them a ring and discuss what you want to do, they're super helpful and will stay on the line giving you advice for as long as you want - you could pretty much get a phone-based training course from them, although to be honest lime remdering is pretty easy, just knowck up a suitable bucket of mortar and trowel it on. I usually trowel on one layer (up to half an inch) and just slap it on any old how, then do a second layer while the first is still wet (although it will have stiffened up a bit while you've been working) so it's easier to put the second layer on, which you can then smooth down either with a trowel or with a float, which ever works best for you. In other works two layers, but one immediately after the other works best.

Finish this off with a few coats of limewash (with a little linseed oil mixed with it to throw off the rainwater) and you'll have the smartest walls for miles around.

Mike Wye will give you loads more advice or post back here and I'll tell you anything else you need to know.

Hope that helps?

Cheers!

Yeah...That's what I meant to say!

Some ones on form today Fatbloke

Cheers Luxo,
Much as I thought really as to the incompatibility of the finish, If staying that would definitely be my preferred method, and I will measure up and then contact the people in your link and see what they say and get a price.

I'd actually love to do it that way, so will have a good look into it, it would also be nice to know the job was right, my only concern there being cost, it can be difficult or at least very expensive getting anything delivered up here and the locals haven't moved on to sympathetic restoration yet but as you say, its easy enough to find out.

Given that a nice rural house here sat in decent gardens will just about buy me a terrace in Lancashire I really am tempted to fix it like the locals, but I think you are right and it would be the better way to go. Good for the conscience too

Cool - let me know how you get on.

You might find another lime supplier nearer, although if you get a bulk delivery the costs shouldn't be too bad.

Some people are scared to handle lime as it's bad for your skin, but I've never had any problems, just wear some latex gloves if handling it for a long-ish period, and don't splash it in your eyes - it isn't "splashy" stuff anyway.

All the best!

I have owned / worked on listed / period property for in excess of 30 years - I cant really add anything to what Luxo has written - other than to assure you that if deal with the right contacts you will not find it much more expensive than sand / cement render and again has per Luxo's words of wisdom - it's far easier to apply

Cheers chaps, will get researching,

over here we use sand & lime mix for jointing & some plastering..ill have to look up the recipe