Feasibility removing pebbledash if you are taking off or repairing pebble dash & render our experience may help

The removal of render or pebbledash could cause damage to brickwork Its a fact brick may be damaged when taking off pebbledash or render

What can be done with the walls once pebble dash has been removed? can you render over pebbledash.These are some of the questions we get asked.

Pebble-Dash, Its been around for many years, nowadays it’s usually cement based but it can also be lime based (more likely to be lime material, if it’s an old roughcast finish)

If applied correctly pebbledash or roughcast can be a very hard wearing finish. Especially good for exposed locations on the correct type of building. Often used on rubble filled walls, the textured finish helps to slow down water and casts rain across the surface of the wall.

Nowadays it doesn’ have to be that pink and white pebble or aggregate the size of golf balls dash. Many attractive aggregates are available such as Quartz,  Dolomite, Barleycorn. It  can even be speckled with green or blue glass

For a look at what’s available in pebbledash spar materials have a look at this link Derbyshire Aggregates

Can you render over Pebble Dash?

This is a question we get asked a lot. Rendering over existing pebble dash can present problems. If the backing render coats are not solid and they fail, then whatever is applied to it will also come away.

Also if the pebbledash has been painted a good key may not be possible. Cracks can form in the old pebble dash layer and appear through the new finish. Definition and neat angles can be difficult or impossible to form, detail such as corners, window frames, stone or brick features etc can get swallowed up and buried in the new render finish. Old metal rusting corner beads that may have been used in the original dash render can quickly spoil any new render or paint you apply. 

If the pebbledash is of a concrete material (which it mostly will be)  it will not breathe, on solid walls, this may cause problems, going over the top of the pebbledash or render finish even in a vapour permeable material such as lime render or a breathable coating will not allow the wall to breathe as the existing pebble dash or render is unable to do so.

How is Pebble Dash applied?

Firstly, a base or “scratch coat of sand and cement is applied this may contain additives such as an integral waterproofer, PVA or latex. Once cured this base coat is normally saturated with water to reduce suction, this reduces the rate of water absorption from the additional render coat. On top of this base, a second coat or “butter coat” is applied. Into this coat (whilst it’s still wet) is thrown the dry dash or aggregate. Some trades then tamper and press the aggregate into the render with a steel float to reduce shedding (common in Spain). A roughcast or harling finish is achieved by mixing the aggregate into the actual render mix and throwing it or “casting” the mixture onto the wall.

Pebbledash and roughcast was a common finish on pre-war houses. Nowadays advances in render technology have allowed for renders that are made specifically for pebble dashing. They are known as dash receivers. Usually, polymer-based they can be coloured to match the aggregate, i.e. white coloured dash render for a white dolomite pebble. Dash receivers are less prone to shed off the aggregate but some loss of pebble will still happen to a degree. 

Wall Finishes should do more than making a house look attractive they are designed to keep the weather out

What are some of the problems associated with pebble-dash or render?

Problems arise when the render fails and cracks develop.

Most pebble dash jobs and old renders will be installed from  “made on site” sand and cement mixes.

Many of these render mixes will be of a poor quality,  with incorrect sand (not sharp) and may not be gauged or mixed properly, it’s just like a cake mix, you have to weigh and mix the ingredients out accurately or the end result may disappoint

When a poor quality render mix has been used usually the render that holds the dash breaks down and becomes friable and powdery.

On a solid wall house, hard sand & cement renders (concrete mixes) are too rigid, they are unable to accommodate movement within the building, they are also unable to breathe

Cracks in render and water Ingress

The main enemy of all render systems, water gets inside the render through the cracks (even hairline ones).

Once moisture gets inside and behind the render, the writing is on the wall (if you pardon the pun) and it will eventually fail 

Freeze-Thaw cycles soon break down the finish, creating hollows within the render and exposing your home to potential damage.

As previously mentioned other problems, more like annoyances can include the constant shedding of pebbles or aggregate.

Pebbledash can also get dirty very quickly and it’s not easy to clean.

When pebble dash looks out of place

On older houses such as a detached cottage, lime based roughcast or dash can look really good and in keeping. if applied correctly and using the right material the finishes can provide good levels of protection and benefits to the building in terms of dealing with moisture both externally and internally. Many properties of the pre-war era were often built with a good quality brick facade, with the upper sections and sides built from lower grade bricks and finished in roughcast. A shortage of building materials and the durability of the finish made this a very popular choice.

But just like stone cladding a pebble dash finish on a period property such as a Victorian terrace can look completely out of place and may cause damp problems. Any render or pebbledash applied ten-twenty years ago is more than likely to incorporate galvanised metal corner-bellcast beads, these beads normally rust and will need removing.

Over the last few years, pebble-dash has fallen out of favour with designers and builders.

Restoring and repairing pebbledash what can be done?

If the backing render coats are solid, pebble dash can be refurbished with a good quality masonry coating. This usually involves patch repairing the render, making good cracks & washing down the surface. Sometimes the surface may need a slurry or “bagging coat” applying which can be cement or lime base. This coat is designed to level out the surface a little and weld the pebbles onto the wall permanently. The surface can then be painted or coated in different finishes such as limewash, silicate or acrylic paints.

If the pebbledash has many defects is causing damp or has broken down and delaminated, or if it looks out of place It may be best to remove it all.

How do you remove Pebble-Dash?

Removal usually involves the use of light mechanical chisels and some “elbow grease” usually the brick or stonework is chipped in the process. This is not a problem if the wall is going to be rendered or refaced in brick, in fact, the scutching marks on the bricks provide an additional key,  aiding the bond of the new render. Although care should be taken,  do not be too concerned about damaging the brick surface during the removal process. If in places some of the backing render is very hard, some small areas can be left in place 

We have come across some unscrupulous firms that try and scare people into leaving defective render on the wall by claiming the walls will fall down during the stripping process, they (the contractors) just want an easy job by going over the old stuff. Some contractors even claim that the stuff they are going to put over the top will hold the old material on the wall, rather like a stabilising coat. That’s just nonsense if the render has come away,  then whatever you stick on top of it will fail. A few firms may suggest pinning the old render behind a layer of fibre-glass and resin or polymer render, then drilling and pinning through the dried layer with steel or plastic hammer in plugs. Not a very good proposal for an old solid wall house.

Going over defective render, It may sound like a cheap and easy fix but it’s not going to do the house much good and will it more than likely fail,  putting you back to square one. Before you make a decision on the refurbishment of render, pebbledash V full removal make sure the walls are hammer tested. This simple test will evaluate how solid the overall condition of the render is. Hammer testing render to assess the condition of it is a straightforward process. Just slide a hammer over the surface or gently tap the render. Any “blown” hollow render will sound different to the solid areas, as it resonates, you will feel and hear the hollow areas.It’s a little harder to do with a pebbledash finish, just tap it instead of sliding the hammer over the surface (make sure the car is not parked too close to the wall!)

 

Many problems with damp can occur as a result of a concrete based dash on old solid walls. 

Once the cladding, cement render or textured coating has been removed from the walls of your home, you normally have to allow for some wall restoration options. From the initial design concept through to the completed renovation stage, you can rely on us to deliver a high-quality service

To find out what the best options are for the external walls of your home, why not arrange an expert survey and receive a written estimate detailing solutions? Just fill in our contact form, provide some information about your project and book a free survey

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