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Posted: Wed Mar 14, 2007 4:02 pm
by PaulS
I'm looking at building a curved wall approx 5.8m long by 1.2m in height. This wall will be built on a slope to create a terrace for some decking - one end of the decking will rest on top of the wall.
I was thinking about building the wall out of standard dense concrete blocks but need to know how to construct this.
I.e should I use single or double skin?, how do I build the arc?
footings etc.
I was also thinking it might be quite hard to build the decking frame to sit on the edge of the curved wall hence it might be easier to support the deck on posts rather than rest on the wall. That way the wall wouldn't be load bearing - any ideas welcomed!
Posted: Wed Mar 14, 2007 8:42 pm
by dig dug dan
I have done a curved wall , and it was easier than i thought.
The trick is setting out and digging the footing. Once I had set out a spray line, I simply dug with an excavator, gradually curving the footing. I have been driving excavators for years, so this was down to practice. You may need to get someone in for this.
My wall was 1.5 high, and was 16m in length, and it was faced both sides.
You will find it difficult to get an even curve using concrete blocks as they are quite long. I would use ordinary bricks, and if the wall is not going to be seen, use rejects or regrades. If the wall is going to be seen, choose a nice sand faced facing brick. and yes, it must be double skin!
As for the decking, just build the frame up to the wall as best you can, and leave it flush with the top of the brickwork, then simply lay the deck boards so they rest on top of the wall and cut them to match the curve.
Hope this makes sense.
If you like, i can post a picture of the wall i built
Posted: Wed Mar 14, 2007 9:43 pm
by Stuarty
We built a crest moon shaped planter, 1m high, out of dense block. As dan rightly said, it wasnt easy using the block, but it was rendered once finished. It took a litte time but it was very good once complete 
Posted: Wed Mar 14, 2007 10:42 pm
by PaulS
I forgot to say I plan to do a smooth render on the wall once done so appearance isn't too much of a worry. Its also quite a shallow curve so presumably I could get away with it using blocks or even grind off the edges once built before rendering.
My main concern was whether to use single block or double skin. If it isn't load bearing (i.e. if the deck was supported on posts) would single skin be ok? My other thought was to build pillars into the wall at each end and in the middle to support the deck.
Also, how easy is it actually to build the curved wall?, I guess you can't use a string line!
Posted: Wed Mar 14, 2007 10:47 pm
by Suggers
Agree with Stuarty & Dan - just finished an internal curved stairwell - bricks, then rendered - brickie did lovely job, which then made it a doddle for plasterer - was almost a shame to cover it up.
ps - why not use blocks on inside (unseen) with bricks on t'other? - just a thought. Would give you a nice curve.
Posted: Wed Mar 14, 2007 10:59 pm
by Suggers
You beat me to it Paul - sounds like you know exactly what you're doing - as Dan says, the secret is to get your footing spot on - are you laying it yourself? Show us your pic Dan, and I'll show you mine..!! ooooer missus.
Posted: Wed Mar 14, 2007 11:20 pm
by Ted
If you are adventurous and not particularly experienced at bricklaying or rendering but think you are OK at carpentry, you could try a poured wall:
http://www.concreteexchange.com/images/fresnobee_1.jpg
Posted: Thu Mar 15, 2007 10:06 pm
by PaulS
Funny enough I did think that might be a good way of doing it but I wonder how the cost compares per m2 to a standard wall in blockwork (assuming the poured wall wouldn't need rendering) & taking into account the shuttering costs.
Has anyone built one of these? - How do you do it?
Posted: Fri Mar 16, 2007 7:02 am
by Ted
You would not render it.
I would pour a footing and have rebar sticking up out of it to give structural support to the wall. I would then tie remesh to the rebar to give added support. It is difficult to explain without a diagram but if you lay sheet material on the ground and draw the curve and cut it out you can ten build up the shuttering using spacers and more sheet material till you get to 1.2m. You can then line the inside with a thin sheet material that will flex to the shape of the curve. You need to make sure your shuttering is well made as the weight of the concrete will cause it to blow otherwise and this will be a messy headache mid-pour. When pouring te concrete in you want to minimise the drop as much as possible and you want to vibrate the concrete ideally wth a vibrator. You can also rap on the forms with a hammer. If you don't vibrae properly the wall will look awful and not be so structurally sound. This is the very basics anyway.
Poured walls are quite common in America but poured curved walls are not so popular as the shuttering costs are more expensive and the carpentry skill are more advanced (but not that complicated really). Also each curved wall is going to have a different degree of curvature so how often is a contractr going to reuse all that sheet material? But sme contractors do have forms made out of 8'x4' sheets that they bolt together to produce walls for poured basements.
The costs of doing a curved poured wall are much higher than building out of blocks but the skills needed are arguably less advanced than for building using blocks and render and so more suited too a beginner.
The main advantages of a poured wall are speed of construction. Concrete walls are meant to be good insulaton-wise too, hence why basements in America are often made this way. But the most pressing reason, IMO, is the sheer beauty of a poured wall. The concrete replicates the exact texture of the form. The link in my post above shows the beauty I am talking about. Zurich airport is another place where you can see this sort of wall.
This book shows how to build a poured wall:
http://www.contractor-books.com/TP/FPBP-Foundations.htm
The book below goes into more detail on how to pour a curved wall:
http://www.amazon.com/Concret....158682X
With the exception of poured walls for basements, poured walls are normally only done on very high spec jobs as they are expensive (and in this country there is little expertise in the area). If you can re-use all that shuttering again the costs won't be too bad but if you can't (and what are you going t do with a load of off cuts of plywood?) the cost if prohibitive unless you like the look of poured concrete.
Posted: Sat Mar 17, 2007 7:28 am
by seanandruby
you have to take extra care when vibrating a one sided shutter as the upward thrust of the concrete will cause it to blow. ???
