I foolishly thought that a control joint in a wall was no more than a break in the wall but now I have read the book more closely it explains that I should use flat galvanised steel pieces to bridge the gap. Seems to make sense but it says that the steel should be embedded in the mortar with (only) the top side of the steel smeared with a thin coating of petroleum jelly which will enable the two joined parts of the wall to slide (bit like fish-plates on a railway line). I do not see the sense in this as surely the underside of the steel will be fixed to the mortar and hence there can be no independent movement between the parts of the wall. If they had said put petroleum jelly all round the steel I could see the logic. Any thoughts?
Control Joints again
- Thread starter bobloes
- Start date
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You're describing a movement joint. Fitting render stop beads back to back (with a 5mm or so gap apart) , either side side of joint in a brick/block wall, allowing movement between two separate surfaces in the same wall. Or,,, you can fit pre-formed movement beading over the joint, again, allowing movement between the two sides. Preformed movement joints have a flexible cover strip down the middle, but if you use back to back render stops, the gap in between would normally be neatly filled up, with a flexible mastic.
Roughcaster Thanks for taking the time to reply unfortunately I do not understand what you are talking about. My ignorance not your explanation. The 60cm high retaining wall that I will build is 11.5 metres long hence why I thought I needed a 'control' joint. Can I build it without any break in its length? There are no piers planned. Cheers
Expansion joints are required in masonry walls. Typically these are at 6 m centres for concrete blockwork and 12 m centres for brickwork. Suitable materials must be used in expansion joints to allow adequate movement of the masonry. The joint must also be finished either by the use of suitable gaskets or mastic – or both – to prevent water penetration. Additional wall ties must be used as part of the expansion joint construction.
Read more: http://www.building.co.uk/story.asp?storycode=1031726#ixzz0iT3QhSwD
Read more: http://www.building.co.uk/story.asp?storycode=1031726#ixzz0iT3QhSwD
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You would need the builders on here to give you some info on the actual building of the wall itself. I think you would need some piers for stability along the length,, but then i'm not a builder. Someone on here will be able to help.
You will need one vertical movement joint in the middle of your wall, you will need to tie one side of the wall into the other one with a few movement joint ties, which are basically like normal ties but with a rubber sock on one side allowing the tie to move in and out of the sock (this is the vaseline bit you're getting confused with). You could probably just wrap a few layers of dpm round one end of a normal flat wall tie instead of buying the special slip ties though as its only a low retaining wall or you may have to but a box of 50 or whatever.
Fill the gap between the blocks with a compressible filler board and if rendering fix a render stop bead to each side of the joint and render up to each bead, fill the gap between the render beads with mastic in a colour to match.
All shall be revealed: http://www.ancon.co.uk/downloads/s1/l1/wall_ties_and_restraint_fixings__feb_2010_.pdf page 17
No need to have piers, a crude rule of thumb for mass (heavy blockwork) retaining walls is that the depth at the base should be about 1/4 - 1/3 of the height. So you should be using 190mm blockwork at least.
As someone else said you should be putting in a movement joint for brickwork around every 12m and blockwork at 6m's.
Retaining walls are slightly different from an external wall in which you would put debonded wall ties (ie. ancon pps). Retaining walls act as freestanding cantilevers (or least most domestic ones are) from the base up, you dont need wall ties between the two sections because they are independant and dont rely on each other laterally.
In the end if your building a masonry retaining wall of 11.5m then you dont need one.
Whilst strictly speaking thats true, what you don't want though, is for over time, one of the walls to settle more than the other and end up with an unsightly difference between the two walls.
Dont normally continue a movement joint into a foundation for masonry shrinkage/expansion thus if one side does settle it would be because it was poorly designed in the first place or inadequate and is failing.
Ahh, nobody likes a smartarse!
Don't mention design though, you know its not been designed!
Muhahah sorry.. i love the word "design" so will branish a lot be warned..Ahh, nobody likes a smartarse!
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