External render of 7nn blockwork

[Kevlar]

Hi all

Can I sanity check some stuff with you more experienced guys?

I want to render a (small) external retaining wall. One side holds the lawn in, and is about 2 blocks higher than the lawn; the other side edges a deck, about four block in height above the deck. The total height of the wall is 5 blocks, laid face down.

I am going to render both sides of the wall; I am planning to make a bench on top out of deckboards. The boards will overhang the top edges by about 50mm each side.

I was going to attach external render end beads to all the faces of the blocks to make it nice and easy to a) terminate the edges and b) make it easier to feather edge the render so its nice and flat. Is this overkill?

Can I use an external grab adhesive to attach the beads? I'm not sure that masonry nails won't make a mess of the high density blocks, and it sounds easier.

Do I need any sort of membrane on the side that faces the lawn? I haven't used any weepholes or anything like that in the retaining wall; I don't think its big enough and the slope of the garden is at 90 degrees to the wall.

I was going to prep the blocks with a water and cement slurry first (not sure what mix to use - 5:1?)

Will plasticiser do as a waterproofer for the render, or do I need both?

I was going to just have one coat of render, not a scratch coat (is that the right terminology?) and a second coat, as the beads that that I was going to use were 12 - 18mm, and I'm guessing this will be within tolerable limits for the thickness of a render.

I was going to use Hansons Heidleburg mortar mix as a render. Not sure what mix of cement to sand this is but it says that it can be used as a render.

Is there anything else that I can do to help prevent the render blowing with frost?

I was then going to paint the render with external paint, PVA the render beforehand?

I've tried to do my research beforehand; sorry if the questions are a bit obvious.

Thanks in advance

K

 

[Micilin]

Hi all

Can I sanity check some stuff with you more experienced guys?

You are in the wrong place if it's sanity you are after - some of us have been staring at walls for far too long

I want to render a (small) external retaining wall. One side holds the lawn in, and is about 2 blocks higher than the lawn; the other side edges a deck, about four block in height above the deck. The total height of the wall is 5 blocks, laid face down.

I am going to render both sides of the wall; I am planning to make a bench on top out of deckboards. The boards will overhang the top edges by about 50mm each side.

[/b] If the boards will throw the water off the top of the wall, this is good. Yu don't want sitting water , or water getting in through the top of the render and ruining th ebond with the wall over time.[/b]

I was going to attach external render end beads to all the faces of the blocks to make it nice and easy to a) terminate the edges and b) make it easier to feather edge the render so its nice and flat. Is this overkill?

Personally I would work to laths (timber battens) but if you are not confident doing this use bead, make sure they are stainless steel. The beads will make it easier, giving you a profile to work to

Can I use an external grab adhesive to attach the beads? I'm not sure that masonry nails won't make a mess of the high density blocks, and it sounds easier. Again, I wouldn't recommend grab adhesive but only because I'm not sure how it will stand up to years of weathering. I see no problem with that type of adhesive if 100% water /frost proof (some one might KNow one?) , as long as none of it is proud of your render as it will intorduce a weakenss for water to enter. I would stick the beads with dabs of render and let them set for a day or two

Do I need any sort of membrane on the side that faces the lawn? I haven't used any weepholes or anything like that in the retaining wall; I don't think its big enough and the slope of the garden is at 90 degrees to the wall.

I think a membrane would be a good idea. I would also think about a few weep holes at the bottom of the wall. You will inevitably get water/moisture/condensation building up behind the wall. It has to go somewhere. You could drill a hole in the joints and use an oiled pipe or dowel or rod in the hole - when rendering is finished, remove the rod

I was going to prep the blocks with a water and cement slurry first (not sure what mix to use - 5:1?)

1:1 :1 sand cement water, brushed . Depends how wet sand is, you don't want it too runny , more soft paste

Will plasticiser do as a waterproofer for the render, or do I need both?

Sovereign water proofer (there are others) will work as a plasticiser too. Don't mix products.

I was going to just have one coat of render, not a scratch coat (is that the right terminology?) and a second coat, as the beads that that I was going to use were 12 - 18mm, and I'm guessing this will be within tolerable limits for the thickness of a render.
2 coats of render for me, scratch coat (keyed with scratcher ) and float coat . YOu won't want to be putting on 10mm in one go

I was going to use Hansons Heidleburg mortar mix as a render. Not sure what mix of cement to sand this is but it says that it can be used as a render.

Is there anything else that I can do to help prevent the render blowing with frost? No sitting water on or behind it/b]

I was then going to paint the render with external paint, PVA the render beforehand?

No PVA . Good masonry paint

I've tried to do my research beforehand; sorry if the questions are a bit obvious.

You've got something to go on know, you'll get more from others

Thanks in advance

K

 

[Kevlar]

Sanity check - lol. Good job. I was driving myself mad going around in circles in my head!

I could be tempted to use timber battens, seeing as I originally tried the battens on the wall to clad board on the side, but an otherwise damn mighty fine plan was put paid to the fact that the B&Q deck boards that I was planning to use as clad, (ptoooh), warped and I couldn't get them flush with the battens without destroying the fixings.

Will 2"x2" be ok? Obviously treated, end grain preserved etc.

Thanks again for the post, really helpful.

K

 

[Kevlar]

Sorry - meant 2" x 1"..

 

[grandwizard]

dont use that heidleburg ****e