What type of render is this?

[markwm]

A row of houses we own have been rendered since we can remember. I have an old pic from the 19th century and the render looks like the same render that is on today.

We'd like to paint the render as it is stained from salts/damp and looks terrible. It also needs patching in places. However, before doing so I thought it best to actually know for sure just what type of render it is. I always thought it was a cement render as it's very very hard but would this be the case if it's been on so long?

When it rains the render goes extremely dark as the water soaks right through, so much so that you can see the layout of the bricks. I've had guys round trying to sell me Andura (water proof coating) and monolastex but I need to do a bit more research before decided on what to put on it. I've looked into lime wash but really need to know if the render is cement before proceeding? how can I tell exactly?

here's some pics:

 

[Moreteyne]

If you can obtain some hydrochloric acid and are able to chip a piece of your render away you will find that the render will fizz in acid if it is lime based. Cement will not.

 

[MdB]

If you can obtain some hydrochloric acid and are able to chip a piece of your render away you will find that the render will fizz in acid if it is lime based. Cement will not.

Lime will always fizz in acid (vineger is cheap alternative). Cement may or may not fizz in acid (some cement contains lime).

No fizz means no lime hence its cement. BUT if you get a fizz, you learn nothing.

 

[chuckey]

First of all I have to say I admire the way the power cables are pulling in the rainwater pipe - very stylish!.
What is the finish? looks like some sort of paint? Its definately post 1960. Looking at the square corners around the windows I would guess its cement. I have never seen lime work with square horizontal corners. Could be a bit of both, lime on house originaly, then when the new windows were fitted, made good with cement, then a coat of paint put on to even things out. Really with a job like this, its best just to use a water seal type product. There are masses of stuff to mask off or paint around and every edge of your new paint will be a potential source of water ingress.
Frank

 

[markwm]

There's no paint on it at all. This is the natural color.

Will try the vinegar thing.

 

[Nemesis]

It looks in the pics to be quite a sandy cement render. Cement and lime look very different. Cement tends to come off in chunks, lime is much more crumbly stuff.

 

[chuckey]

If thats its real colour, I would say its a very weak 6 or 8:1 sand/cement mix, so the sand colour shows. This would explain why it gets wet when it rains. Sorry what I mean is its not impervious. Lime cannot be used in such a diluted quantity, i.e. it always is in shades of white. If its as I suspect, the sand used will be soft sand, no particles greater then about 2mm diam/length. Also the date of it would make it extremely unlikely that its lime. Even now with the resurgence of property restoration, no jobbing builder would use lime on a non restoration project other then when forced to.
Frank

 

[DaveBrigg]

The CO recently identified what I thought was modern cement render as Victorian cement. Put up nearly 150 years ago with hood mouldings cast at the same time, and then limewashed. Just because it appears to be cement, it isn't necessarily modern.
However, we have been advised to remove ours and replace with lime (apart from the mouldings) which does not look to be an option for you. I can see why you want to paint, but how will this look if the rest of the terrace remains unaltered?

 

[Nemesis]

There are plastic pipes coming from the building with nothing which looks like patching around them in the picture. That suggests that the render is relatively recent.

Victorian cement of 150 years ago was a very different beast to what we have nowadays as Portland.

 

[chuckey]

The bridge across the Ax, along the sea front from Seaton, has a sign that says its the first concrete bridge made - 1853, bit weather worn.
Frank

 

[Nemesis]

And not modern portland.

Castle House Bridgwater - one of the first cement houses, 1851, but made from a variety of fairly experimental materials.

 

[CHRIS]

I bet it is not like this!

http://news.xinhuanet.com/english/2005-02/27/content_2626135.htm

One of the first "Modern" ie not Roman cement structures in the UK was the Eddystone Lighthouse 1759 by Smeaton, but the UK was far behind our Persian and Roman friends when it came to cement and concrete technology until this time.

 

[Nemesis]

http://www.dartfordarchive.org.uk/technology/cement.shtml

http://www.bbc.co.uk/dna/h2g2/A476930

http://www.classic-driveways.co.uk/concrete_history.htm





IoE Number: 373965
Location: CASTLE HOUSE, QUEEN STREET (south side)
BRIDGWATER, SEDGEMOOR, SOMERSET
Photographer: Mr John H. Sparkes
Date Photographed: 21 August 2007
Date listed: 16 December 1974
Date of last amendment: 16 December 1974
Grade II*


BRIDGWATERST2937SEQUEEN STREET736-1/10/150(South side)

ST 2937 SE BRIDGWATER QUEEN STREET (South side) 736/10/10001 Castle House 16.12.1974 GV II* House. 1851. For William Ackerman. Brick with pre-cast concrete facing panels, solid concrete, pantile roof with rendered stacks. Double-depth plan including rear range. Early Tudor Revival style. 2 storeys; 2-window range. The front elevation is very ornate, and composed in the manner of an early Tudor gatehouse. The ground-floor walls are constructed in brick with pre-cast concrete facing panels, the walls of the first floor are of solid concrete blocks simulating rusticated jointing. The upper parts of the parapet and mock battlements are rendered brick. Above and below the first floor are friezes formed of perforated pre-cast concrete blocks supported by pre-cast concrete corbels. Projecting concrete drip cills protect the base of the parapets, both friezes and the plinth. The windows are mullioned and transomed 2-light casements with head stops to label moulds. Canted bays to the sides form stair turrets, to front of which, on both floors and attic, are niches with depressed-arched heads, formerly housing painted concrete statues; those to ground floor have head stops to label moulds. To centre of the front is a small single-storey canted bay with a single window and panelled parapet above. The doorway under a hood on consoles is to left and entrance to a stair turret is in the corner to far left. INTERIOR: there is extensive concrete work within the house including staircases, handrails and window frames, all prefabricated at John Board's works. The structure seems to be held together with tie-bars and one section of roof trusses is made out of reinforced brickwork, made to look like a cruck frame or parabolic arch. An early and significant use of concrete, for both decorative and structural purposes. History: probably one of the earliest surviving examples of the use of prefabricated concrete and constructional post-tensioning. The house contains a wide variety of castings, mostly as ornament but with enough items carrying loads to be classified as of minor structural importance; it shows an innovative interpretation of traditional masonry features in concrete and a relatively early method of reinforcement in the structure. Castle House is associated with two important Sedgemoor families, the Boards and the Ackermans; John Board (1802-1861) who extended his family's brick company into cement in 1844, and his grandson William Ackerman who joined the company in 1871 and is credited with the first 'true' Portland cement. -

 

[CHRIS]

I have the dubious hounor of sitting in the same office as a professor of concrete from Tehran university and the engineer who designed the concrete works at Sellafield! I am sure you can understand my enthusiasum for the stuff and also imagine my xmas party - what fun.

I think the Late Joe Strummer (RIP) had something to do with that place

 

[Nemesis]

No, the late Joe Strummer had very little to do with the place, the involvement of the Strummer Foundation was a sideshow really and delayed considerably the rescue of it. They pulled out. It did enable us to have a great street party when it was a candidate for Restoration though.

It belongs to the SAVE Trust, and Vivat Trust is hoping to take it on (must check on progress!) and repair and use it for holiday accommodation.

It's been a long, long haul but getting there.

I actually get quite excited by early concrete, did a fair bit of research for Castle House.

 

[CHRIS]

You would not be so excited if you stood in it all day!

 

[Nemesis]

Only the early stuff!

 

[Nemesis]

More early concrete news:

http://www.24hourmuseum.org.uk/nwh_gfx_en/ART52784.html

 

[markwm]

If you can obtain some hydrochloric acid and are able to chip a piece of your render away you will find that the render will fizz in acid if it is lime based. Cement will not.

Lime will always fizz in acid (vineger is cheap alternative). Cement may or may not fizz in acid (some cement contains lime).

No fizz means no lime hence its cement. BUT if you get a fizz, you learn nothing.

I've now tried this and it did fizz in vinegar, albeit very slightly. Could hardly see any fizz but could hear it. The render is very very hard. With a 2 inch peice I can't even snap it with my hands.

Anyone know of a good place that will do a mortar analysis and recommend what should be used to patch it up and what paint/wash would be best?

 

[markwm]

Here's some close ups...





Also, does anyone know what I can do to improve the brickwork where I have taken the render off?



a) What paint to use. I take it bitumen would be bad idea?
b) How can I remove the remains of the render that are welded to the bricks without totally destroying the brick face.