Rendering - brick

[mo]

Anyone know anything about rendering? As an amateur I had never heard of it til yesterday til a pro mentioned it.

I am going to pave my garden, I have dug up some of the concrete. Now where my shed it, it seems to have been rendered at the bottom to make it smoother. My new paving will probably now be lower that it was before. See picture:

you look hard, you can see a crack - that part totally comes off.

So I will have to re-render it.

Some questions,

How hard is it to do, i it just a case of mixing some stuff together and plastering it on? I couldn't get any decent results on the BandQ or Wickes websites - I imagines something that came in a packet like cement...?

Secondly, would it be better to dig a little deeper and render it all before I pave? So it all blends in properly or should I put in my type 1 concrete and then just render anything over the paving level?

Thirdly, anything to stop me rendering the concrete under the (blue) door ? After the door there is more of the black stuff that has been rendered.

Obviously the entire shed will be re-painted once the paving is done.

Cheers

[John Rumm]

I don't claim any particular expertise in its application - but render is just a generic phrase for an external plastering type of job. The material is typically either a sand and cement mortar, or sometimes, a lime mortar. Its usually mixed similar to a brick laying mortar. Not too strong a mix (it wants to be a parasitic layer on the structure underneath - not so strong as to be a structure in its own right). You can add various additives to it to make it more waterproof etc. It generally "sticks" well to traditional masonry, although you can render just about any material by covering it with expanded metal lath first.

Basically. One usually does it in two coats. A "scratch" coat first (scratch because you scratch up the surface to provide a key for the top coat), and then when that has gone off, a top coat. The top coat can then be finished in various ways depending on the desired texture and your skill.

As with most plastering trowel skills, a main part of the success seems to be knowing when to try polishing it. A classic mistake being to try and do it too soon - typically while applying the finish coat. The trick is to let it start to harden a bit first - then it is much easier to get the trowel marks out. For your application I would guess a fine finish is not going to be critical. A final rub up with a sponge can leave a reasonably attractive result.

Yes, its called cement, and sand! ;-) (or in fact wickes will even sell you a bag of "mortar" which contains mainly sand and a smaller bag of cement buried inside,

Where is your damp proof course? Traditionally one renders down to just above that. (you can get a bit of builders metalwork called a "render stop" which allows you to finish a render coat with a nice neat edge).

You can render it if you want the appearance to be the same as the rest.

[mo]

Ahh thanks, makes sense

I am going to need mortar for my paving anyway so I will have it available to hand.

[NT]

Rendered walls should generally leave a strip at the bottom unrendered for evaporation of damp. Classic render mixture is 1:1:6, ie by volume

1 part cement, 1 part builder's lime, 6 parts sharp sand.

If the wall is stone or old soft brick its better to use lime, 3 parts sand to 1lime. Lime render needs rounded corners.

There are differing ways to render. If your house suits a modern perflectly flat finish, go with John's polished render. If you want a softer finish better suited to an old house, it can be applied in one coat, trowel only briefly to pretty much level it, then brush it very gently with a paint brush dipped in water to get rid of the trowel lines and give a smooth even finish.

NT

[John Rumm]

Another easy to do and rustic looking finish is stipple. You can do one or two coat for this. Trowel flatish, and wait for it to go off a bit and then use a broom head or dustpan brush to tamp the surface. the bristles leave little dimples all over and they erase all the trowel marks etc.

[The Medway Handyman]

Wickes do a ready mixed product in a plastic tub specifically for repairing render. It has fibres mixed in which apparently reduce cracking as it dries & it sticks really well. Anywho, its very easy to use & get a decent finish with if you are a rendering numpty - like me.

Expensive if you are doing a large area, but worth the price IMO for smaller repairs.

I'll have a look at the tub later & find the exact name & SKU.