Advice constructing garden building on sloped slab

Discussion in 'Builders' Talk' started by Rienne, Feb 8, 2016.

  1. Rienne

    Rienne New Member

    Hi, can anyone offer advice please?

    I have a 20ft x 12ft mesh-enforced, insulated and DP'd, concrete slab that I have planned to build a garden workshop onto.

    Because I was originally going to build a wooden construction, the formwork was built with a 2% fall - or 3" slope down the 12ft sides.

    I'm now considering bricking, or blocking, the 2 sides and rear, and making the front frame and doors with wood. It will be a flat roof to keep within regs. (Because my garden has been excavated lower than my 3 neighbours however, I may go loose with the 2.5m height limit if I can reverse the extra without too much trouble).

    So, because the slab slopes down towards the front, I'm not so sure how to go about brick or blockwork for the sides...

    As far as I can tell, I should use type 2 engineering bricks for the first and second course and then DP, and then blockwork up. But I'm just guessing! Should I do make the first course by cutting the bricks into wedges to make level? Or do I use rebar some way, wedge cut blockwork to level and fill with concrete? Or cut blocks to level and not use rebar? Or should I shutter a long wedge along both sides to make level with concrete - to the width of a block, and continue up with more block?

    Do I even need a damp course if the slab itself is DPM-lined?

    I'm so not sure. And I don't have a book to explain what to do here. I much appreciate any help or related guidance.
    [​IMG]

    Of course, I can still make it from wood. I just have priorities for sound and heat insulation, hoping to maybe install a wood burner against the back wall, and I'd prefer to avoid any more wood maintenance. I think I could use some pointers from a smart person!
     
  2. What finish will the outside be given - exposed brick or render?

    Anyhoo, I think what I would do is to run a single row of bricks (total 3" high) along the (low) front for appearance, and simply shutter and make sloping concrete fillets for the sides and back (although the back prob won't need it).

    Then build up from this level base.

    I suspect you should still have a DPC 'cos that slab (is that going to be your inside floor?) is not much above the outside ground level, and the DPM should be brought up to your DPC level and bedded in.

    Pros will be along to clarify.
     
    Rienne likes this.
  3. Rienne

    Rienne New Member

    Hi, thanks for replying!

    I'd render - as I think I'd be using mostly block for the back and sides.

    There won't be any brick at the front. I'm keeping a 50mm elevation save for the ramp/pathway to be flush level with an entrance (I want to be able to roll a motorbike in/out).

    Yeah you're right, the back is level across the 20ft so doesn't need any workaround.

    Interesting you say about 'fillets'. So it's a method used I take it? As I say, it was just a guess. Is there - I don't know how to put it - a recommended 'footing' ratio if I do this? As in, if blockwork on top (now level), should I shutter for 1 1/2 x the block width for example, or would same width be OK? Thanks.
     
  4. Rienne

    Rienne New Member

    Yeah, see, this is where I'm dumb and don't understand how DPM and DPC's work, despite having looked at diagrams. I don't know how I'm supposed to "bring the DPM up to DPC level and bed in". Or if I still can. Does it look like I can from my photo? Thanks.
     
  5. sospan

    sospan Screwfix Select

    You can get around the 2.4m limit by putting in a small pitched roof - it doesn't have to be a traditional central line ridge, it can have a different pitch front and back.

    It depends on the external finish of the brick / block as to how to address the slope - are you going to render it ?
     
    Rienne likes this.
  6. Rienne

    Rienne New Member

    Oh, do you mean I can pitch it lengthways (slopes front and back), and that would allow higher?

    As the sides and rear won't be visible I thought I'd use more block, and yes then render it.

    Thanks
     
  7. sospan

    sospan Screwfix Select

    Yes, the eaves have to be 2.4m but you can go upto 4m at the ridge.
     
    Rienne likes this.
  8. Rienne

    Rienne New Member

    Ah, I forget - I can't. Too close to boundaries. I think I can only get away with the 2.5 flat roof.
     
  9. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Ask a pro, but isn't one way to level, to build up with slate ?

    Like starting with an inch of mortar and slate at the back, building up with extra layers of mortar and slate til you reach the required height at the front(4" in this case).

    Mr. HandyAndy - Really
     
    Rienne likes this.
  10. Phil the Paver

    Phil the Paver Screwfix Select

    You could easily lose 3" in the joints as you go up making the top course level all the way around, just set profiles up front and rear adjusting the course measurements as you go up.
     
  11. Jeepers, peeps - chust run a bludy row of bricks along the front, set in mortar and tapped down until it's 3" high.

    Then set some basic shuttering along both sides - anything will do, even gravel boards with blocks against them to keep them in place. Obviously mark out the outside line accurately-ish.

    Then dump in some concrete and use a manageable length of straight timber (say 2 metres of 3x2) and a spirit level to level off the sides so's they go from 3" at t'front to zero at t'back.

    Jobbie jobbed - a pretty level base to start yer brickying from.

    I don't know what to do about the DPM, tho' - the one under that slab looks as tho' it'll be on the outside edge of the wall?

    Peeps?
     
  12. Rienne

    Rienne New Member

    Yep, the DPM is on the outside! Well darn, that makes it basically useless then, I bet. Seems I was ill-advised...

    As for laying bricks along the front - I would do this for the corners and framing, but I had intended to keep the front low and unbuilt, at least for the doorway meeting the path, for easy roll in and out of motorbikes.

    Ok, so now I have more of a 'clue', I believe I now need an 'alternative' damp-proofing method, like using SynthaPrufe.

    Thanks
     
  13. Ah, of course - soz, Rienne. You want to leave the front at 'slab' level?

    In which case forget the bricks along the front and chust do the shuttering bit - really quick and easy.

    Two lengths of anything straight and at least 3" high - position either side of the required area, hold in place with blocks and fill with concrete. Use spirit level and tamping straight-edge as before.

    First take a level from one side to the other to ensure the highest points at both fronts are at the same height.

    That's the easiest way to get a level 'found' for you to start bricking/blocking from.

    As for the DPC, I'm not sure what to do there. Are there any founds outside that slab area which you could build your brick walls up from, or does it have to be on that actual slab?

    What do the pros on here suggest?
     
  14. Rienne

    Rienne New Member

    Thanks Devil's, no worries, I don't think I made that clear before. Thanks for the shuttering tips and the new word, 'found'!

    Though as for the DP. Yep it's a pickle - thanks for the idea. But I can't go on the outside now as I had to re-route the land drain pipes that ran a little high in the hardcore (across the length), to around the back, using osma pipes and reducers, then filled with shingle. Would'nt make a good base to build onto of course. Then, down the left hand side, I've also got a provisional pipe for the electric cable, filled with shingle. So no room to manoeuvre there. Typically, despite trying, I'm finding things out the hard way, oh well!
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice