workshop build?

[nickson71]

Hi all

I've just started building my first workshop ....... it'll be small (3 x 2.5m) but I live in a mid terrace. Anyhow by saying I've started I mean I spent the day ripping down the old outside toilet and coal shed


My plan is to dig out some basic foundations and put in a low brick wall then use timber upward

3x2 or 4x2 timber frame with 600mm centres. outer face will have a 18mm ply facing followed by shiplap to look pretty. The back and one side wall will be the exciting stone wall of the yard. The roof will be done using the same framing timber cross battened using 50mm thick battening (to allow air cap) followed by 18mm ply and finished of with 2 or 3 layers of felt. Insulation will be 75 or 100mm depending on which timber I use. by vapour barrier and ply or plaster board on internal faces

My only query at the moment is what to do with the floor ..... at the moment I'm thinking that once the first layer or two of brick is complete I should dig out further add a layer of hard core followed sand then damp proof membrane. Once this is done I'll add another layer of brick to the walls then back fill with concrete then timber build upwards.

does this sound OK and if so what sort of thickness do I need of each floor layer


any ideas, advice or suggestions will be greatly received

Thanks

Ian

 

[OLD]

Insulation in the floor is worth having say 2 inches either above or below the slab, finish with easy sweep chipboard if above.
When laying the base set the brick work at or above level required see above and use a tamping board straight or stepped to level the 4-5 inch concrete scratching along the part built wall.

 

[nickson71]

thanks for the info OLD


another idea I was just toying with was building the brick walls with damp proof membrane then laying joists across then build the timber frames on the floor joists. Insulation between joists held off sub floor using plastic netting or a large sheet damp proof membrane looped over joists.

I guess there has to be air flow to keep the joist dry but that shouldn't be too hard

This way should be easier to complete and hopefully not as expensive and kinder on knees

just need to find out what size the joists need to be for a 2.5M span and what spacing.... first guess would be 4" x 2" at 400mm centres

Ian

 

[RogerS]

Why not build a concrete slab, as close to Building Regs as you want to go especially as they are very good when it comes to recommendations for insulation etc. Stick some mesh in to give it extra strength for when you put in your machine(s).

Once the slab is good and dry, then build your timber slightly oversize so that the sole plates overhang the concrete by a few cm and ensure you cut a drip channel on the underside. Also ideally make the sole plates so that there is a raised edge on the inside (if you follow me). Then build the rest of your frame on top of the sole plates.

That way, any rain on the outside will run down the outside and most importantly run off and away rather than drip inside. If you have good DPM in your concrete then you should be snug and dry.

 

[PowerTool]

4x2 should be quite okay for 2.5m (8')
Quick rule-of-thumb I read somewhere for maximum span for joists was:-
joist depth (in inches) x 2,+ 2 = span in feet,so 4x2 okay up to (4x2+2=) 10'/3m span.
After this,of course,you need to consider if you will be putting lots of heavy machinery in :shock:

Andrew

 

[davidc1075]

You need 38x147 for a span of 2.5m at 400 centres using C16 for a loading of 1.5kN/m2. 4x2 is not up to the job. Got the load tables if you really need to sleep at night.

 

[OLD]

You could just lay a base previous insulation sudjestions still apply, set up shuttering and cast then build up of it, say 5 inch thick under walls 4 inch rest. Clean/cut up shuttering and use as studding/wall plates.
4 inch ready mixed concrete on a well prepaired site will be more than enough for any machinery . 18mm ply and shiplap is over kill for walls go thinner and fix with panel adhesive then fix shiplap through to studs.
The above save time and money but your ideas will work fine.

 

[Adam]

3x2 or 4x2 timber frame with 600mm centres.

Just worth checking if this is the standard width of rolls of insulation? I can't remember offhand if they are 600mm, or 500mm? Anyway, make sure you choose a width that allows you to roll the insulation straight in without cutting.

Adam

 

[Jake]

Instead of beefing up the joists you could stick a sleeper wall down the middle to halve the span.

 

[Sonic]

outer face will have a 18mm ply facing followed by shiplap to look pretty

Just a thought, but why do you need to put 18 mm ply under the shiplap ? A damp-proof membrane should be enough, surely - save you quite a bit of cash.

Colin S

 

[nickson71]

I maybe going over the top with 18mm ply but I want the extra security that comes with going over the top ...... I live in a mid terrace that has got a back street /ally behind so adding to my paranoia :shock:

I'm leaning towards the concrete option ... I've got loads of bricks that could be used as hard core, once smashed up, now the old toilet and coal shed are down.

my last concern would be finding the mains water and sewer pipes as they all come in the back ......... I'm not sure if I should concrete these in or go for the wood floor option

 

[ratkinsonuk]

Ian, I had the same quandry a few weeks back (https://www.ukworkshop.co.uk/forums/viewtopic.php?t=8684) but after some deep thought, and conversations with a few people, decided on a wooden subframe.

Basically, I'm still going for breeze-block footings around the perimiter to set the frame on, but I'll be putting in a set of footings down the centre to bridge the span for floor joists.

With a 6 inch air gap between soil and floor, and air bricks each end, I should be fairly dry.

The upside of my decision is a lot of cost and time saved, digging out a whole for the slab and then filling it in with concrete. The downside is that I may loose a few inches in height due to the 5x2/6x2 joists.

I'd be interested in what choice you finally make and what other problems/experiences you encounter.

My intention is to be water tight by August (cash flow allowing), so I can start to roll my tools in before winter sets in.

Rob.

 

[nickson71]

Hi Rob

I decided to go down the concrete route .........

the nature of my build would of involved digging down as I still had the base from the old outside toilet and coal shed to remove

the digging out was completed last weekend using a pick axe, shovel and wheel borrow and 100mm hardcore has been placed ....... The only problem encounter was being let down by a friend (hungover) and a family member (can't crumble about this one as she have just had injections in both feet). I managed with help from my other half to fill 3/4 of a 8 ton skip on Saturday and the rest on the sunday. Sunday was removing all the old bricks so the digging out was done in a day.

This Saturday I'm hoping to get the base cast I just need to get to my local builder merchant and get the materials ordered

the overall stucture is going to be
100mm hard core
25mm sand
DPM
insulation 50-75mm
followed by 100mm Concrete

the slab is going to be cast using shuttering


Ian