[Rienne82]

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.

*Or should this go in the Construction group?

 

[Rienne82]

Or should I just make it out of wood? It's just that insulation - sound and heat (UK), combustible, hoping to maybe install a wood burner against the back wall, and wood maintenance.

If anyone knows what the smart person would do, that doesn't make things more expensive, please give a girl a hand. Thanx!

 

[Bondo]

Ayuh,.... If ya poured just a slab, without thickened edges for a footer, I'm guessin' ya won't have the strength for a block/ brick buildin',...

How thick is the slab,..??

 

[Rienne82]

Ayuh,.... If ya poured just a slab, without thickened edges for a footer, I'm guessin' ya won't have the strength for a block/ brick buildin',...

How thick is the slab,..??

Thanks for replying. I'll put my sketchup image up and post the dims below.

6" type 1, 2" sand, DPM (and up around slab - not in image), 2" kingspan, DPM layed over kinspan, 3 x A142 Mesh overlapped and tied, on chairs, 3.7m3 of C20 concrete. (5" at front to 8" at back, flat - not thickened edges/footings).

 

[mako1]

I would pour a level curb on the slab edge and then go from there with whatever you want.

 

[Rienne82]

I would pour a level curb on the slab edge and then go from there with whatever you want.

Thanks mako1. It's one of the ideas, I just have not heard of it as a standard.

As it's a slope, 1/4" per foot, would you use rebar too, and then into hollow blocks? Thanks

 

[mako1]

I would use a piece of #5 rebar every 4' @.You can insulate your blocks with something like vermiculite.

 

[Rienne82]

I would use a piece of #5 rebar every 4' @.You can insulate your blocks with something like vermiculite.

Thanks mako.

OK, so I presume the first course be hollow blocks and concrete, and #5 rebar every 4'. Then hollow blocks filled with vermiculite as I go. (I'll have to do some research on this, not seen any videos on using vermiculite).

You wouldn't suggest using, for the first course, 7N dense (not hollow) blocks angle cut to level (no rebar) then DPC, then follow upwards with hollow blocks?

Thanks

 

[mako1]

I think either way would work.When I was building lots of block structure we always used a piece of # 5 rebar 4'@ center and then filled those cells with concrete and then fill the cells between with vermiculate for insulation.I'm sure there is probably a better material than vermiculate these days.
If it were me I would form and pour a concrete curb.This way would be easier to go with a wood framed structure if you choose to.

 

[Rienne82]

Great, thanks mako!

Ok, I'm leaning towards that idea of pouring a concrete curb using short bits of rebar to cut to level. How far into the slab should I drill down would you say, 3"-4"?

And how wide should the curb be for strength, would same width as a brick be sufficient?

Thanks

 

[mako1]

It all depends on the type of structure you decide to build.If I was in the UK and building a wood structure I would make the curb 5 1/4" so you could frame the walls with 2 x6 's for better insulation.
If going with block I would use 8" to match the block.
I have had wood stoves in several wood framed structures.I put a piece of 1/4 aluminum between the wall and stoves with standoffs as a heat shield.In this area a wood structure is both quicker and cheaper than block.It also allows you to easily attach shelves and cabinets to the walls.

 

[jomama45]

Sawing/ripping block for their length takes quite a bit of time, especially w/o a large concrete saw. At the same time, forming and pouring a concrete curb takes some time as well.

Hopefully, Stuart45 (a mason/member here from the UK) pops in with a better idea with materials that are readily available to you.......

 

[stuart45]

What type of wall were you thinking of building? eg Cavity, solid 9 inch, solid 4 inch with 9inch piers. What finsh on the walls? eg facework or render.

 

[Rienne82]

Hi Stuart. Ok, so I think solid 4 inch with 9 inch piers, rendered. Just as a 3-sided plinth (rear and sides - and not very high, not sure how high just yet) for timber upper. The rear and sides won't be visible as they're adjacent to fences. I'd render anyway for what it's worth.

Presumably I'd have another 2 half piers on the sides, and 3 along the back, plus the corners?

Thanks

 

[Rienne82]

Hi Stuart. (This is a rewrite from before - ran out of edit time)...

Ok, so I think *either of the solid options, and rendered.

Would be just as a 3-sided plinth (rear and sides - and not very high, not sure how high just yet) as a base for timber upper. Full timber front.

The rear and sides won't be visible as they're adjacent to fences. I'd render anyway for what it's worth, for the added weather protection.

Presumably if solid 4 inch with 9 inch piers I'd have another 2 half piers on the sides, and 3 along the back, plus the corners? ... *I think solid 9 inch might be the better and easier option.

Thanks

 

[stuart45]

LBC common bricks have a deep frog and are really easy to cut down, so these are often used where you need to level out a base. 3 inch is roughly one course to nothing. As you get to where the bricks can't be cut any thinner use a few pieces of roofing slate bedded on mortar.

 

[Rienne82]

Ah ok thanks. Do I shave the frog side?

 

[stuart45]

Yes, cut the frog away as needed with a brick trowel, brick hammer or hammer and bolster.

 

[Rienne82]

Yeah ok, just to update. Real slow progress but weather's been terrible in my area until recently. Got the plinth sorted and ready for the frame

Frame is currently planned using 38 x 140 x 2440 (only length available) timber. However, I'm considering upping to 47 x 150 x various (3000,3600,4200,48,54,60,72), as I'm really not so happy about 38. Second opinions welcome on that one. Rafters to be 47 x 200 x 4200 /or 4800 (span ~ 3500 + overhang).