Workshop design (Finally Progress!)

[Crispylettuce]

I'll add them to the list of things to look into. Thanks.

 

[Crispylettuce]

Sorry in advance for the wordy post!

I am finally back onto this project after various other jobs took priority – although have hardly any completely free weekends over the coming month! I have now moved the old shed to a temporary location and am starting to progress the designs.

Quick recap:
• Current working dimensions 3.5m x 4.2m x 2.8m high.
• I am working closely to Permitted Development, and the building will be within 1m of the boundary. I’m able to ‘steal’ some extra height because of the way the land lays around the plot.
• Brick dwarf wall and insulated timber frame on a concrete base (the ‘Mike Approved’ method!)
• Cladding TBC!
• Thinking about using Onduline sheets for the roof as I hope they would look better than EPDM – although admittedly I have no experience with either! Any suggestions?

The Site:

• Next job is to tidy this area up (includes putting in a short retaining wall of sleepers next to path - red line approx)…. and get some better measurements of the site.
• Unfortunately the old concrete slab I had hoped to just extend wasn’t even covering the footprint of the old shed (blocks/earth had been used along one edge!) so will have to lay a new base.

• This is a rough proposal to give an idea of the usage of the site and where restrictions are. The ‘current retaining wall’ will be re-profiled to give better access to the new ‘shop.

Design:
I would like to get my design straight whist I start on the groundwork – and could do with some feedback from all you knowledgeable people. My main questions relate to the roof initially.
• Pent or Pitched? – I’d prefer a pitched roof for aesthetic reasons, but maintaining the PD height doesn’t allow much of an angle. Is 15deg enough for a pitched roof to look ‘good’? (I appreciate its subjective)
• Overhangs – How much is ‘in proportion’ for a building this size?
• Rafters/Joists – Maybe a Mike question, but what size of rafters/ridge beam would I be looking at for either a pent or pitched roof? (Is it simple enough to refer to some Span Tables?).
o For the pitched roof, do the joists need to be the same height as the wall plate? Or can it be higher?

Thank you all for your patients – and hopefully answers to the questions above.
If anyone has any comments/suggestions then feel free to shout!

I have tried to keep on top of the various builds going on - which have been inspirational. I attempted to start collating various bits of information from them, but it became a bit unmanageable!

Thanks, Chris.

 

[Dan0741]

Chris no idea on the technical details, but make sure you have a window on the back to benefit from that immaculate view!

 

[Crispylettuce]

Yeah - you might be right. It is fantastic this time of year. I'm thinking of a window back and side.

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[Malc2098]

I don't want to be a killjoy, chaps, but shed burglaries (which includes workshops) occur when the burglar can see what's in the 'shop and worth nicking without being seen by neighbours and the house.

So an access at the rear, a window, which is a weak point, would be favoured by the burglar.

 

[Mike G]

I completely agree, Malc. I put an internal shutter into my workshop over my only window, so that the buggers wouldn't know if the 10 minutes it took to break in would yield them a couple of old shovels and a collection of painted tin soldiers, or a whole lot of bright shiny new tools. (It's neither of course).

 

[RogerS]

.....I put an internal shutter into my workshop over my only window, so that the buggers wouldn't know if the 10 minutes it took to break in would yield them a couple of old shovels and a collection of painted tin soldiers, or a whole lot of bright shiny new tools. (It's neither of course).

The shovels are brand new and the soldiers yet to be painted :lol:

 

[AndyP]

I don't want to be a killjoy, chaps, but shed burglaries (which includes workshops) occur when the burglar can see what's in the 'shop and worth nicking without being seen by neighbours and the house.

So an access at the rear, a window, which is a weak point, would be favoured by the burglar.

Indeed there are some who build their workshops with no windows at all for precisely that reason.

One day I will get around to making some external shutters for mine as is the norm around here until then I make do with a venetian blind.

 

[Crispylettuce]

Already in the plan for some blinds/shutters. It's surprising how much more exposed the garden feels now the shed is gone!

Can anyone help with the roof?


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[9fingers]

Already in the plan for some blinds/shutters. It's surprising how much more exposed the garden feels now the shed is gone!

Can anyone help with the roof?


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I expect timber tables would say 175-200 timbers at 400/600 centres for the pent roof but then you could hold a dance on top!
Gut feel would say 150mm would be fine.
Agree a pitched roof would be nicer. rafters 150mm, ridge board 175/200 x 25 and (vital)ceiling joists omitted in your drawing 100mm for no storage or 150 if you are storing stuff up there (won't be a lot of room at 15 degree pitch.
Overhang? joists 50mm over the wall plate say plus fascia board, with roof decking a further 75mm to drain into 100mm gutters.

How does that sound.

Bob - hammer chewer builder

 

[Crispylettuce]

Cheers Bob - much appreciated. Span tables I looked at were very comprehensive, but its helpful to sanity check these things as all new to me.

I need to talk with the domestic planning department (wife) to see if we want to go above PD (and whether to do it officially or not). Our gardens are long so buildings don't directly affect anyone, and the four nearest properties to mine all have buildings that are larger than allowed under PD so couldn't have any reason to complain. If we did build higher than PD (without permission) we would have to accept the risks, but it sure would provide a lot of useful storage for a house without a garage!

 

[Mike G]

.......Can anyone help with the roof?.....

Sorry Jon, I've not been around much lately and missed this.

For a start, I would suggest that if you build a duo-pitched roof that you consider using 22.5 degrees for the pitch. The reason is that this is the minimum for slate, and you might one day want to put on a more traditional and durable finish than Onduline. With Onduline (or equivalent), use more battens than they suggest. The stuff seems to have got thinner over the years, and can sag in the heat of the sun. Also, don't bother with anything other than black, because no matter what colour you buy, they all end up black in a year or three.

Flat roof? I'd want 195x45 joists at 400 C's for that span.

 

[Crispylettuce]

The stuff (Onduline) seems to have got thinner over the years

Thanks for the heads up. I remember using some Onduline years ago and it seemed fairly bomb proof at the time. I might need to have a look at other options - the is always EPDM/rubber but it isn't very interesting to look at!

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[RogerS]

I thought Onduline was something you put on a nasty rash :lol:

 

[9fingers]

I thought Onduline was something you put on a nasty rash :lol:

We bow to your extensive experience in such matters Roger :lol: :lol: :lol:
Bob

 

[Crispylettuce]

I bet Mike's glad he mentioned Onduline now to drag this up!

 

[Phil]

I thought Onduline was something you put on a nasty rash :lol:

We bow to your extensive experience in such matters Roger :lol: :lol: :lol:
Bob

:lol: :lol: :lol:


As long as the rash is not between the big toes .......... :lol:




Let's get back on track chaps.

:text-threadjacked:

 

[Crispylettuce]

Back to workshop related matters!

What is the guidance with the position of rafter ties/joists relative to the wall plate?

I'm currently looking at 25deg pitch roof. 150x50 rafters on 600 centres. based on advice above, I'm looking at 100x50 ties/joists and a ridge beam of 175x25.

My question is can I put these (say) 150/200mm above the wall plate without any concerns?

I know other builds have joists above the wall plates, I'm just not sure what the compromise is? A larger ridge beam?

Thanks - as always!

 

[9fingers]

I've got a very similar section roof. Ties are about 400 above wall plate level and bolted through.
Bob

 

[Mike G]

Back to workshop related matters!

What is the guidance with the position of rafter ties/joists relative to the wall plate?

I'm currently looking at 25deg pitch roof. 150x50 rafters on 600 centres. based on advice above, I'm looking at 100x50 ties/joists and a ridge beam of 175x25.

My question is can I put these (say) 150/200mm above the wall plate without any concerns?......

Yes. The general rule of thumb is to keep a raised tie in the lower third of the rafter, otherwise you have to beef up the rafters.........and either use guesswork, or get an engineer involved.

If you are tying every truss, the ridge board is of no structural significance whatever, other than as a place to locate the top of the trusses. You can make it of anything you want, so long as it has a large enough vertical face to enable a decent fixing to the rafter end.

 

[Crispylettuce]

Here is my working plan. It's still basic, but starting to get a good idea for where I'll end up (hopefully). Stud work is on 600 centres at the moment, and I need to add the extra framing around where the windows/doors will be. Have been on the lookout for for Windows!

I'm planning on leaving the centre two rafter-ties out to provide access to the modest storage areas.

Have also been looking into various roofing/cladding options.

I'm under no illusion that this is going to be a long build!

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[9fingers]

I can completely see why you want to leave out those central ties but I wonder if it might not be prudent to beef up the ridge board to 47mm thick to help stop the wall bulging outwards in the storage access area.

Mike G might have a view on whether I'm being over cautious.

HTH
Bob

 

[Crispylettuce]

Yeah. That's a fair point and on my list of checks. Last thing I want is bendy walls!

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[Mike G]

......I'm planning on leaving the centre two rafter-ties out to provide access to the modest storage areas..........

Then forget what I said about the ridge. You will need something beefy to span the gap, going at least 1200 past the "gap" each way. I'd suggest that you use a 195x45 for the ridge in that area. It turns into a pain having different thickness ridgebeams, because you have to cut the rafters differently, so I suggest you simply run this the whole length of the ridge.

 

[Crispylettuce]

Makes perfect sense Mike - Thanks!

Over the next couple of weekends I hope to get the necessary retaining wall (relatively small - two sleepers high) before I can mark out my proposed shed for final sign off from “Household Planning” (my Wife!). Frustratingly I only have two full weekends over the next six weeks!

This is clearly pushing me into the likely (inevitable!) scenario where it won’t be finished this year. Whilst I am aiming to replicate Mike's build methods (albeit with my skill & experience level!) I’m thinking of changing the order of things around a little and getting as much as the exterior done first, before returning to the inside to insulate and clad with OSB. The only problem I can see is with the insulating after the cladding is that you will be pushing it in against the building wrap and batons – not something solid like the OSB.

It will be something I’ll have to review as I go along.

 

[greeno]

The only problem I can see is with the insulating after the cladding is that you will be pushing it in against the building wrap and batons – not something solid like the OSB.

It will be something I’ll have to review as I go along.

This is simple to overcome. Just make a little depth jig, the thickness of your insulation then use panel pins, tack them in half way at the depth of your insulation. you only need 4 per piece of insulation. This will give you something to butt up against if the insulation board is a bit loose. This is what I did on an outhouse conversion and it works a treat.