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David's Workshop Build

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David's Workshop Build

Postby Regex » 26 Mar 2021, 19:14

Hi everyone

First time poster here, though you can find me over on UKWorkshop too.

I have been busily researching and planning a workshed build to replace an existing dilapidated shed, and have a couple of questions which I've numbered that I'm hoping someone can help me with. I have lots of diagrams and pictures to help explain the situation and any issues I'm not sure about, as there are a number of confounding factors :eusa-think: I'm a newbie with building, so if you can see any issues that seem obvious to you, which I might not have thought about, please do point them out.

The Workshop
I am planning to make it 8' by 12', with a flat roof (orientation not decided yet) and it will primarily be used for hobby and diy projects with hand and battery powered tools only (so no heavy machinery). It will be built with wood stud framing, and insulated and water proofed. I will need to get planning permission since this is within the grounds of a listed building, so no need to worry about permitted development issues related to height.

Q1: Does it matter which way I slope the flat roof?

Diagram 1.png
Diagram of proposed build
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Foundation - 9' 1 1/2" x 13' 6"
There is already a concrete foundation here, and it was built by some previous owner at an unknown date (I have lived here for a year now). I would prefer not to have to make one myself.

  • It is close to soil level on some sides
  • The concrete foundation (2") appears to have been cast in two sections on top of reclaimed bricks (~5")
  • The surface is rough and pitted, but uncracked.
  • Water collects and does not dry well..

foundation dirt.JPG
Camera angle one on the diagram above.
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foundation depth.JPG
Foundation depth
(192.96 KiB)

foundation pitting.JPG
Pitting in foundation
(343.87 KiB)

foundation wet.JPG
Water on foundation
(213.02 KiB)


As you can see it is not in great condition, but it feels strong and stable.

Q2: Can I re-use this foundation?
Q3: If yes, can I clean/prep it to prevent water/dirt collecting in the rough surfaces?
Q4: How much space should I leave on the edges of the foundation closest to the guy and on the right?

Boundary Wall
There is a boundary wall that is over a foot high(pics below). The problem with this is that this is ground level for the neighbours, and they have a large vegetable patch there. As such I am worried about surface run-off and damp issues. I am thinking of leaving a foot of space between the workshop and the wall.

Q5: Will water pooling be an issue?
Q6: Should I try and prevent rain as much as possible by extending the roof to create a guttered overhang?

Diagram 2.png
Rear view of proposed workshop
(304.46 KiB)

boundary wall.JPG
Picture of boundary wall and soon to be ex-shed.
(195 KiB)

As you can see it's quite damp, although that might be because I just swept up the winter's leaves. The wall is in quite a state as the previous owners dumped a lot of stuff back there.

Shed Base
I am thinking of following Mike's how to build a shed without concrete design (with the 145mm suspended floor).

Q7: Would this approach work here?
Q8: Would I need to cement the reinforced lintels down?
Q9: Would I need to apply mastic to the inside of the lintels to prevent water ingress?

That's all for now, thanks for reading this far and looking forward to your replies :)

-David
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Re: David's Workshop Build

Postby Mike G » 27 Mar 2021, 12:07

I'm busy, so just brief answers . Welcome, BTW.

1/ Slope it the short way, unless there is a really good reason not to. And slope it towards where it is easiest to deal with the water coming off the roof, especially if you are connecting to a drain.

2/ It's not a foundation, really, but yes, it's enough for a small shed like this, presuming it is the same sort of thickness throughout. Your issue is going to be that it is bigger than your proposed shed, so there is the potential for water to gather on top and seep through the plinth of the new building.

3/ I suggest laying a fillet of sloping concrete on top of it after you have built the plinth. This will help water run away from the building.

4/ Enough to fit a broom in comfortably.

5/ See 2 & 3

6/ That would help, but remember you can't overhang the boundary.

7/ Yes

8/ Or bed them on mastic/ construction adhesive.

9/ Not on the inside (the lintels themselves won't let any water through), but the joints should be mastic, yes.

Sorry about the brevity.....
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Re: David's Workshop Build

Postby Regex » 28 Mar 2021, 20:44

Hi Mike

Thank's for the tips!

1) No drain, just water buts and overflow. I think I'll angle it down towards the boundary wall so that I don't get too much rainfall in between the low wall and the shed.

2, 3) Are you suggesting something like what I found on the screwfix forum here (including painting with bitumen sealent)?

4) I suppose the broom width gap is moot if I am making a sloped fillet?

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Re: David's Workshop Build

Postby Mike G » 29 Mar 2021, 08:24

If you blackjack the base and wall first, then the fillet won't stick. You can do it afterwards on the outside of the fillet, but you don't seem to have an edge to stop against on the slab, so I don't know whether it's worthwhile. The fillet alone, done properly, should solve the problem. I have the same detail on my greenhouse/ potting shed, and I'll simply be doing a fillet. Concrete, not mortar.

I would definitely make the gap wide enough to clean. Leaves and other debris can quickly build up in voids like that and they retain moisture very effectively.
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Re: David's Workshop Build

Postby Regex » 30 Mar 2021, 12:27

Ok, I will just go with a simple concrete fillet then. I might get back to you with more specifics on that later on.

With regards to the lintels, soleplates and periscopes: It seems that the pericopes are much higher than the sole plates, and thus would protrude into the base plate of the walls. This doesn't seem right, am I looking at the wrong periscopes, or will there be about 15mm of mortar to make up for the gap?

Also, is my lintel placement/size ok? it's the best I could do given the 8' x 12' size constraints. I'll have to figure out a way to plug the gaps.

See diagrams for reference:
lintel placements.PNG
Lintel, periscope and sole plate placements
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Rytons periscope specs.PNG
Ryton's periscope specs
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On a side note, I have started reading this other workshop build by Michael and you answer a lot of questions that I might have there already, so I hopefully won't need to bother you too much :D
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Re: David's Workshop Build

Postby Mike G » 30 Mar 2021, 13:17

Ventilation periscopes are made of insubstantial plastic, and can be cut to length with any old thing you have to hand, from a Stanley knife to a fine saw.

Rather than leave gaps like you've shown, it might be better to cut two shorter lintels to produce a snug fit. Or, as you are going to be casting concrete anyway for the fillet, you could clamp some timber either side of a lintel to make formwork, and infill with a strong concrete mix.
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Re: David's Workshop Build

Postby the bear » 30 Mar 2021, 16:46

The periscope grill is designed to replace a brick usually, not a piece of timber hence the height difference.

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Re: David's Workshop Build

Postby Malc2098 » 30 Mar 2021, 17:34

As the periscopes come in two pieces, to slide one inside the other to adjust for height, I seem to remember shortening mine to achieve the desired distance between the courses.
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Re: David's Workshop Build

Postby garindeathray » 08 Apr 2021, 17:31

Mike G wrote:Rather than leave gaps like you've shown, it might be better to cut two shorter lintels to produce a snug fit.


How unpleasant is it to cut these lintels?
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Re: David's Workshop Build

Postby 9fingers » 08 Apr 2021, 17:49

garindeathray wrote:
Mike G wrote:Rather than leave gaps like you've shown, it might be better to cut two shorter lintels to produce a snug fit.


How unpleasant is it to cut these lintels?


Noisy, dusty angle grinder job but relatively quick. Make sure mrs and neighbour don't have their washing out!

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Re: David's Workshop Build

Postby Regex » 08 Apr 2021, 22:09

9fingers wrote:
garindeathray wrote:
Mike G wrote:Rather than leave gaps like you've shown, it might be better to cut two shorter lintels to produce a snug fit.


How unpleasant is it to cut these lintels?


Noisy, dusty angle grinder job but relatively quick. Make sure mrs and neighbour don't have their washing out!

Bob


Thanks for the pointers everyone, but this is beyond the ability and kit that I have :D
I'd have to mortar them together anyway, so I'll just fill the gaps with bricks and mortart or just pour cement.
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Re: David's Workshop Build

Postby Mike G » 09 Apr 2021, 07:50

I'd suggest that of those two options you list, you'd get a better job by pouring some strong concrete. Because there is no foundation, bricks and mortar would start cracking up fairly soon, particularly with frost movement. Clamping a piece of wood either side of the gap and pouring in a bucketful of 4:1 concrete is probably an easier job than bricklaying anyway, and has a better chance of lasting.
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Re: David's Workshop Build

Postby Regex » 09 Apr 2021, 18:31

Does that mean 1 (cement) : 2 (fine aggregate/sand) : 4 (coarse aggregate) ?

I've never made concrete before, would hanson cement be ok?

Can I re-use gravel from the garden path as my coarse aggregate?
coarse aggregate.PNG
Coarse aggregate
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Re: David's Workshop Build

Postby Mike G » 09 Apr 2021, 19:32

I know this is a regional thing, but in this neck of the woods concrete is made from ballast (stone and sand ready mixed). I seem to remember than in parts of the Midlands, for instance, it is specified by cement: sand: stone. My 4:1 was cement to ballast, and I'm afraid that I don't know how that breaks down sand: stone. You certainly can't use those stones from your garden. They're too big. You need "20mm stone" (or 3/4" stone), which is the mesh size of the seive they use at the pit.

You might be better off buying a post-hole mix from a local builders merchant. As for Hanson cement....all cement is much of a muchness. Any brand will do.
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Re: David's Workshop Build

Postby 9fingers » 09 Apr 2021, 19:45

the calculators here might help for cement /sand/stone mixes

https://www.pavingexpert.com/calcall#ca ... nd-mortars

But I'm not sure if C7.5 or C20 is called for here.

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Re: David's Workshop Build

Postby Regex » 16 Apr 2021, 10:11

Thanks for the calculators.

So by my estimations, for the mortar for a perimiter lintel wall of 12ft x 8ft (total length 40ft) plus another layer to bed the base plate on top of the lintels, I make that 80ft (24.384m) of mortar length.

At 0.1m width, that makes an area of 0.1 x 24.384 = 2.4384m2.

For this the Bricklaying Mortar calculator gives me 133kg building sand and 38kg cement (ratio of 3.5 sand : 1 cement).

Does that sound about right?

I'll work out the concrete infill later too.
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Re: David's Workshop Build

Postby Regex » 16 Apr 2021, 10:13

RE: the concrete infill:
Mike G wrote: My 4:1 was cement to ballast, and I'm afraid that I don't know how that breaks down sand: stone.


Are you sure it's not 4:1 ballast to cement? Seemsl like a lot of cement otherwise.

I can get ballast here in Scotland.
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Re: David's Workshop Build

Postby Mike G » 16 Apr 2021, 13:43

Regex wrote:....... (ratio of 3.5 sand : 1 cement).......


Absolutely categorically not. The only time you use a mortar that strong is for ridge tiles and between tiles up the verge of a roof. Bricklaying mortar is 6:1. Don't listen to anyone who tells you different.

And yes, 4 ballast, one cement. That's only for your particular circumstance, where it tapers to zero. Otherwise, again, 6:1 ballast: cement is normal concrete.
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Re: David's Workshop Build

Postby 9fingers » 16 Apr 2021, 13:56

Mike G wrote:
Regex wrote:....... (ratio of 3.5 sand : 1 cement).......


Absolutely categorically not. The only time you use a mortar that strong is for ridge tiles and between tiles up the verge of a roof. Bricklaying mortar is 6:1. Don't listen to anyone who tells you different.

And yes, 4 ballast, one cement. That's only for your particular circumstance, where it tapers to zero. Otherwise, again, 6:1 ballast: cement is normal concrete.



No Idea why that site is advocating such a strong mix. Generally they have had quite a good reputation for a good few years.

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Re: David's Workshop Build

Postby Regex » 16 May 2021, 23:52

Mike G wrote:
Regex wrote:....... (ratio of 3.5 sand : 1 cement).......


Absolutely categorically not. The only time you use a mortar that strong is for ridge tiles and between tiles up the verge of a roof. Bricklaying mortar is 6:1. Don't listen to anyone who tells you different.

And yes, 4 ballast, one cement. That's only for your particular circumstance, where it tapers to zero. Otherwise, again, 6:1 ballast: cement is normal concrete.


Thanks. Apologies for the long delay, just getting back to this as I have been waiting for a while now on planning permission (still not in :x ).

So just to summarise:
Mortar for bedding lintels and sole plate: 6 Sand : 1 Cement (EDIT: Changed from 4:1 to 6:1)
Concrete infill between lintels and concrete sloped filets: 4 ballast : 1 cement.

I will be drawing up my first delivery order soon I think.
Last edited by Regex on 17 May 2021, 16:18, edited 1 time in total.
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Re: David's Workshop Build

Postby Mike G » 17 May 2021, 08:20

NO! Mortar and concrete are 6 to 1 other than in exceptional circumstances. A concrete fillet tapering to zero is an exception, and 4 or 5 to 1 there would be better.....in that particular circumstance. I come across this a lot. I have no idea why people are being led into over-strong mortars in particular, which are a really bad, harmful idea. Over-strong concrete is a waste of money, but doesn't actually have a great downside structurally.
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Re: David's Workshop Build

Postby Woodbloke » 17 May 2021, 08:47

Mike G wrote: I have no idea why people are being led into over-strong mortars in particular, which are a really bad, harmful idea.


Our house was built in 1947 and for some strange reason, the entire South facing wall was constructed with what seemed to be almost pure sand as a mortar mix. I had to have it entirely re-pointed a few years ago which took a pair of brickies two days; at the rate I could do it, it would have taken me two years :lol: - Rob

Edit - they used a 4:1 mix 'cos I remember asking them
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Re: David's Workshop Build

Postby Lurker » 17 May 2021, 12:18

Woodbloke wrote:
Mike G wrote: I have no idea why people are being led into over-strong mortars in particular, which are a really bad, harmful idea.


Our house was built in 1947 and for some strange reason, the entire South facing wall was constructed with what seemed to be almost pure sand as a mortar mix. I had to have it entirely re-pointed a few years ago which took a pair of brickies two days; at the rate I could do it, it would have taken me two years :lol: - Rob

Edit - they used a 4:1 mix 'cos I remember asking them


Most likely lime mortar.
If you use cement mortar to repoint, it will fail quite quickly.
You can buy ready mixed lime mortar in a tub.
What I did was take a bit out and quickly reseal the tub.
How big the bit is depends on how quickly you get bored with pointing- when I get bored, I start to get sloppy.
The upside is you can do a little at a time without lots of preparation as there is no mixing to do.
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Re: David's Workshop Build

Postby Mike G » 17 May 2021, 12:36

Lurker wrote:......If you use cement mortar to repoint, it will fail quite quickly.........


Worse than that, even, it can cause the bricks to spall.
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Re: David's Workshop Build

Postby TrimTheKing » 17 May 2021, 13:59

Mike G wrote:
Lurker wrote:......If you use cement mortar to repoint, it will fail quite quickly.........


Worse than that, even, it can cause the bricks to spall.


Why's that Mike?
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