Hully's Workshop Build - Summer Update

[Hully]

Hi All

I'm about to embark on my workshop build so thought I'd post it up and contribute to whats been a massively informative and inspiring forum for me - particularly Mike and Jimmy's build threads so thanks to both of you.

I'm building the workshop at the end of our garden under permitted development with a certificate of lawful development issued by my local council.

The garden is 9.3m wide, so to stay within permitted development the workshop is going to be 5m wide (around 4.8m internally) and 5.3m long (5.1m internally). I have a builder lined up to do the slab next week as I have zero experience in that area but I'll then be doing pretty much everything else myself.

Its going to be built in a similar way to the other workshop WIPs on the forum - basically an insulated timber frame sitting on a concrete slab/brickwork with larch featheredge cladding, a tile hung vented "cold" roof and double glazed french doors and window.

At the moment I'm planning on building it as follows:



If it all goes according to plan it should hopefully look something like this:



There are a few "unknowns" in my head regarding the construction, mostly around finishing off the roof with sofits etc, so I'll be asking for advice along the way

All feedback welcome.

Cheers
Hully

 

[Malc2098]

Hi Hully.

Good luck with this. Yep, it's a good forum. I wouldn't have got half so far in planning mine without all the experience and knowledge shown on here.

I can't offer much because I'm at about the same stage as you.

ATB

Malcolm

 

[kirkpoore1]

That's pretty thick for a whole slab, isn't it? I can see deeper footings, of course, but 8" thick concrete for a slab seems like overkill.

Kirk
Not a structural engineer...

 

[Hully]

Hi Kirk

I was actually worried it wasn't enough!!

My builder checked with a Building Control Officer on another one of his jobs and he suggested a 200 mm reinforced slab...I think because the soil here is mostly clay.

THB, I'd rather go overkill to be sure it wont give me problems down the line.

Cheers
Ed

 

[greeno]

Your breather membrane detail looks funny. You seem to have two sole plates and you're sandwiching it between the two, bringing it into the inside.

Also, your DPM, you've just put it on top of the slab. I'd expect it in between the hardcore and slab on top of a blinding layer.

What are you using for floor insulation? If it is celotex or similar it can just float. No need for batons.

 

[greeno]

OSB doesn't make the best floor material (I know from experience). T and G chip or ply.

Any reason why you are overboarding OSB with plasterboard?

If you just want plasterboard finish them swap the OSB for a vapour barrier.

 

[Mike G]

Hi Hully.

This looks like another nice workshop. It cheers me no end to see so many good buildings going up these days.

200mm is a chunky old slab. I'd only do that if there were nearby trees, but, other than to your wallet there is no harm whatever in overdoing things here. I have a little personal thing about the cladding overhanging the brick-line in the way you propose. It doesn't bother everyone, but be warned, that overhang will be 60 plus mm. I built a house like that once, and can barely look at it these days!

With the floating floor and DPM above the slab, you'll need a good floated finish on the concrete. Is your builder aware of this? Powerfloating, if that is what you propose, has to happen when it has to happen, even if it is the middle of the night. Hand floating doesn't produce such a polished finish, but the timing can be a bit more flexible.

 

[Mike G]

Your breather membrane detail looks funny. You seem to have two sole plates and you're sandwiching it between the two, bringing it into the inside.

I've misled people before now with that detail. I think the dashed line you are looking at is the tie-down strap.

Also, your DPM, you've just put it on top of the slab. I'd expect it in between the hardcore and slab on top of a blinding layer.

It is possible to put it above the slab, as shown. It just requires a very smooth slab, and very careful building practices, such as keeping everything very clean and free of debris.

What are you using for floor insulation? If it is celotex or similar it can just float. No need for batons.

Indeed. Nor battens :lol:

 

[greeno]

Mike, if you really wanted to put the damp proof layer on top of the slap you could just tank it with a couple of coats of black jack couldn't you?

 

[Mike G]

Mike, if you really wanted to put the damp proof layer on top of the slap you could just tank it with a couple of coats of black jack couldn't you?

You could, but that stuff is like satan's snot. Horrible to work with.

 

[9fingers]

You could, but that stuff is like satan's snot. Horrible to work with.

Hmm! I'd not seen it available in green! :lol: :lol:

Bob

 

[Hully]

Hi Hully.

This looks like another nice workshop. It cheers me no end to see so many good buildings going up these days.

200mm is a chunky old slab. I'd only do that if there were nearby trees, but, other than to your wallet there is no harm whatever in overdoing things here. I have a little personal thing about the cladding overhanging the brick-line in the way you propose. It doesn't bother everyone, but be warned, that overhang will be 60 plus mm. I built a house like that once, and can barely look at it these days!

With the floating floor and DPM above the slab, you'll need a good floated finish on the concrete. Is your builder aware of this? Powerfloating, if that is what you propose, has to happen when it has to happen, even if it is the middle of the night. Hand floating doesn't produce such a polished finish, but the timing can be a bit more flexible.

Hi Mike

Thanks very much for the feedback.

Agree with you on the overhang, but increasing the thickness of the brickwork and the walls and bumping out the bottom featherboard seemed like a lot of effort to avoid the overhang. I'm sure hindsight will run up and smack me in the face once its done though :?

I've told the builder I want a smooth and level floor, so had assumed he'd hand float it, which hopefully should suffice for a floating floor on top, which will be Celotex. I had thought of putting the DPM between the hardcore and slab but with the ground level ending high up the slab I thought it would be best to keep it above the ground level and therefore on top of the slab. What do you think?

Cheers
Hully

 

[Hully]

OSB doesn't make the best floor material (I know from experience). T and G chip or ply.

Any reason why you are overboarding OSB with plasterboard?

If you just want plasterboard finish them swap the OSB for a vapour barrier.

Hi Greeno

Thanks for the feedback on the floor, I'll look at T & G chip...I've seen it elsewhere on the forum as the floor with a painted finished and it looks good.

I've used OSB on the inside to kill two birds with one stone. It acts as sheathing (as when traditionally used on the outside) but also acts as the moisture barrier if used on the inside so I can avoid using plastic sheeting/caulking etc. It looks like they've starting using this technique quite a bit in the States so figured I'd try it that way.

I could then just paint it rather than overboarding with plasterboard (and may still do that depending on how the budget goes) but I'd rather have a nice finish and having it plastered will help sell it as a "garden office/playroom" if we ever put the house on the market.

Cheers
Hully

 

[Hully]

Your breather membrane detail looks funny. You seem to have two sole plates and you're sandwiching it between the two, bringing it into the inside.

I've misled people before now with that detail. I think the dashed line you are looking at is the tie-down strap.

Correct Mike. Sorry, its not very clear but the dashed line is the tie-down strap.

Also, your DPM, you've just put it on top of the slab. I'd expect it in between the hardcore and slab on top of a blinding layer.

It is possible to put it above the slab, as shown. It just requires a very smooth slab, and very careful building practices, such as keeping everything very clean and free of debris.

I had considered putting the DPM between slab and hardcore but as the groundlevel finished high up the slab I thought it would be better to keep in on top of the slab. Happy to be corrected though if it wont be a problem underneath the slab

What are you using for floor insulation? If it is celotex or similar it can just float. No need for batons.

Indeed. Nor battens :lol:

Yep, Celotex.

 

[Hully]

The first days work on the foundation is complete!!

Following the feedback here I talked to my builder and we've agreed to change the foundations to the below. It seems to be a better solution and my builder says its a better overall foundation - I wasn't sure about the wall foundation and the slab being separate but my builder says its absolutely fine and how they would do it for house extensions etc. Feedback welcome if you think there are any issues.



And here's a picture of the progress so far. It should be finished by Saturday and then the fun starts!!



Cheers
Hully

 

[9fingers]

MOD NOTE: Hully, Your post had a broken link in it. I hope I've fixed it correctly, if not apologies - Bob

 

[Hully]

MOD NOTE: Hully, Your post had a broken link in it. I hope I've fixed it correctly, if not apologies - Bob

Thanks Bob.

 

[Hully]

Quick update:

Foundations are now complete and overall pretty happy with them. My one slight annoyance is that the sole plate has been screwed to the brickwork in a few locations so the DPC has been broken in those locations. Not the end of the world though I suppose and nothing can be done about it now anyway.

Regardless of the screws I'll still use galvanised strapping screwed to the slab to secure the sole plate which will be this weekends job. Timber is on order so walls should be going up from next weekend.

Thanks for looking

 

[Malc2098]

Looking good! My digger arrives Monday!

 

[Mike G]

........ My one slight annoyance is that the sole plate has been screwed to the brickwork in a few locations so the DPC has been broken in those locations. Not the end of the world......

No, it's not the end of the world, but if you can undo the screws a bit and raise the plate by an inch or so, then squeeze a circle of silicon around the screw, then so much the better.

 

[AndyP]

Must be a thrill to be out of the ground like that. Don't envy the build at this time of year. Hope the weather holds

 

[Dan0741]

Nice work Hully, looking good.

 

[Hully]

Looking good! My digger arrives Monday!

Bet you can't wait Malcolm. Looking forward to seeing your build!!

 

[Hully]

........ My one slight annoyance is that the sole plate has been screwed to the brickwork in a few locations so the DPC has been broken in those locations. Not the end of the world......

No, it's not the end of the world, but if you can undo the screws a bit and raise the plate by an inch or so, then squeeze a circle of silicon around the screw, then so much the better.

Thanks for the tip Mike. I'll definitely try to get some silicone in there.

 

[Hully]

Must be a thrill to be out of the ground like that. Don't envy the build at this time of year. Hope the weather holds

I've not really done anything woodwork related for nearly 6 months (since we moved) so can't wait...though I'd certainly prefer it to be sunny and 25 outside

 

[Hully]

Nice work Hully, looking good.

Cheers Dan!!

 

[Hully]

Made a bit of progress today though nothing too exciting.

I've fitted all the galvanised straps to the slab and chiselled out sole plate in the respective places so the framing can sit flat on the sole plate over the straps. I've put in 3 per side...so one every 1500ish mm.



Overall not bad progress for 2 hours work but I'm a bit p1$$ed off as I think I've gone through the DPM. My builder said the slab was over 100mm deep so I played it safe and used 80mm screws but I felt a bit of give while drilling holes so assume the slab isn't that deep near to the brick work, presumably because the DPM wasnt push right into the corner where the brick meets the foundation.

I guess the only thing I can do if I have done through the DPM is back out all the screws and stick some Silicone down the holes.

There are only 12 holes so its not a swiss cheese but not sure if I'm being overly worried about this so what do you guys think? Will it be a major issue if I have gone through the DPM and is it worth sticking some silicone down the holes.

 

[Robert]

More expert opinions may vary from my inexpert one but I wouldn't worry about the DPM - just carry on.

I doubt silicone would make any difference anyway.

Your drawing only shows 2 sides of your build. Are there any more windows than shown? I often wish I had more natural light in mine and I have windows on 2 sides.

 

[Hully]

More expert opinions may vary from my inexpert one but I wouldn't worry about the DPM - just carry on.

I doubt silicone would make any difference anyway.

Your drawing only shows 2 sides of your build. Are there any more windows than shown? I often wish I had more natural light in mine and I have windows on 2 sides.

Hi Robert

Thanks for your thoughts. I'll definitely crack on regardless as I have no choice (can't take the concrete out and do it again ) but I may chuck some silicone down there anyway just to make myself feel marginally better.

I'm not putting any more windows in for two reasons really. The first is cost (especially velux's etc) but the main reason is that its a very shady area of the garden with large trees and bushes enclosing it in on 3 sides so windows on the other sides wouldn't be hugely beneficial. The front will get sun on it most of the day and there's a lot of glass on that side so it should be relatively bright, plus I'll be putting in lots of "zoned" lighting as well.

Cheers
Hully

 

[Hully]

Hi All

After a hiatus of a few weeks due to weather and socialising I've managed to break the back of the framing with the help of a mate on Sunday. As you can see, all the walls are up and the ridge beam is in so noggins, roof rafters and ceiling joists next, as well as an additional wall plate to tie the 4 sides into each other.





I'm then thinking the following:

- Put in temporary diagonal bracing on the inside
- Cover roof and walls with breather membrane
- Clad walls
- Tile roof
- Insulate walls
- Fit door and window
- Replace bracing with OSB
- Then onto plastering, flooring, sockets etc etc etc

The reason I'm thinking of using this approach is so that I keep the OSB and insulation as dry as possible over the next few months. What do you guys think? Any issues with my thinking?

Cheers
Hully

 

[Mike G]

Spot on, Hully. Makes sense to get yourself a dry working area ASAP at this time of year.

 

[Malc2098]

Looking good!

 

[9fingers]

Spot on, Hully. Makes sense to get yourself a dry working area ASAP at this time of year.

I think I might also try and get some guttering up even if it is a temporary lash up. It will save mud and water splashes over your nice new external cladding and reduce having a muddy mess to work in.

Bob

 

[Hully]

Spot on, Hully. Makes sense to get yourself a dry working area ASAP at this time of year.

Thanks for the reassurance Mike, glad I'm thinking along the right lines

 

[Hully]

Spot on, Hully. Makes sense to get yourself a dry working area ASAP at this time of year.

I think I might also try and get some guttering up even if it is a temporary lash up. It will save mud and water splashes over your nice new external cladding and reduce having a muddy mess to work in.

Bob

Good idea Bob, I'm sure I can bodge something together until I get onto trimming out the exterior properly

 

[Hully]

Looking good!

Cheers Malc

 

[tabs]

Looking nice. Did you say the windows will double or single glazed?

Did you use pressure treated timber? Just wondering as if the cladding is pressure treated and you have breather membrane is it wrth it?

 

[TrimTheKing]

Looking great Hully, any further progress…?

Cheers
Mark

 

[Hully]

Hi Guys

Been making slow but steady progress over the last couple of weeks. The top plate in now on, temporary diagonal strapping on the inside is done and all the noggins have been fitted. I'll get a picture up later

In the mean time I had a couple of questions I was hoping to get some advice on:

1) I was planning on putting the roof rafters and ceiling joists on 600mm centres but having read around 400mm seems to be far more common. As this is only a workshop I had assumed 600mm would be OK but now having second thoughts. What do you guys think?.
2) The insulation I'm planning on using comes in 400mm wide panels so rather than use 400mm centres on the wall I used 440mm so the gap between each joist would be 400mm. I'm now wondering if this is a balls up as I'm guessing the gap needs to be smaller to ensure a tight fit and good "seal". It's obviously too late to change the walls but just trying to work out if this is likely to be an issue or not.

Hope you all have a good New Years.
Cheers
Hully

 

[Hully]

Looking nice. Did you say the windows will double or single glazed?

Did you use pressure treated timber? Just wondering as if the cladding is pressure treated and you have breather membrane is it wrth it?

Cheers Tabs. Window and door will both be double glazed.

All the framing is PT. Cladding will be Larch which will then be painted.

On whether its worth it or not that's a good question. The cost difference is pretty negligible and I like play on the safe side so for me it was a no brainer but you could well argue it might be overkill.

Cheers
Hully