Hovis builds a garden office*

Interesting. I'm not very good with really understanding these vapour barriers. So what would happen if I leave the gaps open? Isn't the fact there is a continuous vapour barrier behind mean the water won't condense there? I have trickle vents on the bifold doors in case that helps. At the end of day surely it's impossible to make it gapless? Eg bottom of the walls clearance from floor / skirting. Normally that's caulked against wall and under skirting will have a little gap with the floor.

Let me know your thoughts, I don't want to balls this up at this stage. Thanks.

Update! Had a plasterer come in to do the ceiling. He did a pretty decent job, although it's a bit wavy at the edges which doesn't look great with the crisp edge of the wall panels, but that's mostly me being anal as usual. After the skim I set about cutting up the birch plywood. I went for 12mm as it was a fair bit cheaper than 18mm and plenty strong enough. Cutting to size was straight forward enough, lots of measure measure tracksaw. I used 3mm window packers to help with maintaining a consistent gap, the laser level came in very useful too. Spending ages getting everything nice and square during the construction phase really paid dividends here. Thank you very much for whoever it was @pryally ? who suggested I stagger the boards. I think it looks significantly better this way than vertical boards would have.

I used lost-tite screws, which have a very small head and a nice T10 driver. I spent 10x longer than I otherwise could have by making sure all screwheads were in line with one another and evenly spaced (I may decide to leave them exposed)

I've also put in all the spot lights and ghetto rigged a plug to them connected to an extension reel from the house. Finally some proper light.

It's all coming together, need to decide on flooring and skirting next. I was originally thinking of going for oak (laminate or engineered wood), but now I'm not sure. If any style folk have an opinion I'm all ears, it needs to be 12-14mm thick though so it's flush with the door threshold.

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Looks amazing! Proper nice job on the ply walls.

That top edge would bother me too. Can you caulk it?

My wife and design collaborator suggested a cork floor. Think you can get engineered cork-faced boards, or just glue tiles down like old school lino tiles. Would warm the space up and reduce reflected noise a little.

Looks amazing! Have you tried to heat it yet and does it retain the heat if so?

Looks great.
So - did you leave gaps?
I'll try and give an explanation of how I think the vapour thing works...
The interior space is warm and humid (relatively), so there is usually a pressure from inside to out. Your warm humid air is trying to get out through the walls. If it gets into the bit with insulation, then as it passes through the insulation the temperature drops and you get condensation. The middle of walls is a bad place for that to happen, that's why you use a vapour barrier on the warm side of the insulation - so that water vapour can't get there. But vapour barrier won't stop condensation on the room side of it, it's to stop vapour getting through. Although it's the warm side of the insulation, the face of the wall is still a bit colder than the interior of the room, so the theory about sealing the ply with more permeable silicon is that the vapour will pass through the joints (due to the general low-level pressure for air to try and get out through the walls), and because the joints are more or less sealed, it can't ventilate out again, so it's stuck there getting damp between your ply and the vapour barrier. If you leave actual gaps, air should be circulating enough that you don't get a build up of damp/condensation.

Thanks! Perfect explanation I think, it makes perfect sense. I have indeed left them as gaps for the reasons you describe. I do want to caulk the top edge though for aesthetic reasons as @dbr mentioned. I guess I could use a proper sealant instead. I did have to make a big gaping hole in the vapour barrier for the wires into the consumer unit to pass through, I think I'll sealant around it and that should minimise any water vapour getting through there. Could also box it in with a decently sealed door.

@dbr Thanks. Cork would look good I reckon, I worry about its spongyness with my heavy machines and rolling things around though. I'll get some samples in and see. I'm also thinking a light grey would look good.

@7ven Haven't tried to heat it yet, I still dont have real power there and it's also very dusty and smelly so I'm leaving the window open 24/7. I'll wait until I've got the proper electricity connected and then I'll give it a go. Need to decide on a heater too, I was looking at these radiant / convection heaters by duronic on amazon, but they advise not to keep them near walls, which for my case with my fancy plywood wall is probably double important. I'll probably just get a plug in oil heater.

thus looks amazing, unless you've done this type of work its very difficult to understand the extra work which is involved in setting everything out with consistent gaps to the boards and screws -great work! Glad the idea of staggering the boards worked out
I never considered the detail between the plaster skim and the boards would be so pronounced. In hindsight a shadow stop bead or skim bead prior to boarding would have helped?

Is it too late or do you not have space to install electric underfloor heating? would save on losing wall space and give more uniform heat.

Maybe a rubber stud tile? Nora do some but they may make it difficult to roll your machines round? or maybe marmoleum? Forbo are a good product

Thanks. I don't know enough about plastering to be able to say what should have been done, but yeah, some kind of edge stop detail to keep them straight would have helped. I wonder if I should have put the plywood up first and let him skim onto it? It's not as bad as it looked in my previously posted pictures; I haven't put in all the screws on the top edge yet so most of the panels are bowing towards the room making it look worse. If I run out of things to do over christmas I might just take down the top panels, scrape the low points and make it more even and then put them back up. A lot of faff for some minor aesthetics though, but it is bugging me.

I didn't consider underfloor heating tbh, I assumed it would be more expensive than I was willing to spend and more work. I think I'll be happy with a roll around electric heater. Most of the time I spend in there will be work shopping so I'm moving around staying warm anyway.

Thanks for all the flooring suggestions, I have much to mull over. I think I'll do the window and door reveals next and hopefully the weather will warm up so I can stick the cladding onto the sides and free up the floor.

Our basement workshop (100m2) stays pretty temperate all year round with no heating and a single glazed drafty glazed wall at one end. Even now I only get cold if I stay still for too long - good motivation!

I’d stick with a cheap, temporary heating option.

something like this fitted after boarding or a similar plastic one forming a shadow gap would have worked. Don't think Skimming up to the plywood would have worked, you would have staining on the boards and a crack would form with no neat way to finish it.

Both my garages are without heating which is just about bearable for a couple of hours but after that it gets uncomfortable, but the spec on your build is much higher. You can get some pretty thin electric under floor heating systems which are easy to lay but certainty more expensive than an oil filled radiator.

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Its a common problem that I run into regularly at work. Spreads always seem to leave a bulge of plaster at the top and bottom of a wall, this leads to frequent arguments between chippys such as myself and plasterers as when we come round to fit skirting boards we have to hack off big lumps of plaster in order to get the boards to sit flush against the wall without massive gaps between the skirting and the wall. Traditionally this was solved by fixing grounds (a thin piece of timber with a 45 degree chamfer cut into it so that a lip sticks out of the wall) to the wall below the line of the skirting, this did two jobs:

1. A straight consistent edge to the plaster so that there are no bulges.
   
2. Solid fixing to nail skirting to without the use of things like gripfill.
   
   

With regards to the ceiling / wall join, there is a reason why lots of houses have coving as it is an easy way to cover up wobbly or bulging plaster.

As @pryally says a strip bread would have helped you here but hindsight is always 20/20.

As I see it your options are:

1. Attack the bulges with a sander, messy but it will level it out.
   
2. Run some kind of coving or fillet round the edge of the ceiling.
   
3. Get used to it.
   

Hi all. Does anyone have any ideas on the sexiest way to do the reveals for the door and the window cill? I've tried using plywood, with any without a shadow gap and I don't like the look of either. I think the problem is how shallow they are.

I'm starting to think a corner L shape trim that will frame the door, painted anthracite grey but I kinda think that will look not so good either. Any design ideas most welcome!

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Could you try it with a shadow gap but paint the bit of the timber in the reveal to match the window colour..?

Solid oak could look nice. Think I prefer the shadow-gap but hard to say from photos.

You could try doing a stop mitre on the boards on the reveal. Cut a 45 along the exposed edge of the board using a track saw or table saw and another on an offcut of the same length. Put them on a flat surface and push the 2 points of the 45 degree cuts together so they touch and back this with masking tape on the face. Then flip the whole thing over and put a bead of CA glue along one of the cuts and pull them together, give it a spritz with accelerator and it will hold. This way it will look more like solid birch than birchply.

Skill builder / Robin Clevett have started a garden room series. Should be interesting comparing construction methods, Robin always does amazing work…

https://www.youtube.com/watch?v=nOgFByYgsGY

Looks like we all watch the same stuff on youtube :)

Was very interesting to see how professionals do it. Once the Glulams and eco joists appeared I got somewhat jealous. I do find it odd that these screw piles are claimed to be cheaper than a concrete base though. Maybe the basic DIY screws can be, but I don't believe those ones they used with the installation and the fancy subterrain scanning would cost any less than a slab.

I think @TW is planning on using screwpiles for his though, would be interested to know which supplier he goes for and the cost, I could be way off.

I'm going down the pilings route using cardboard forms.

At some point, I should possibly have an engineer do some fag packet calculations, but my own suggest that 12 pilings, each 300mm diameter & 600m deep, using high strength concrete and a bit of rebar, should support many times the weight of the office I have planned.

It will also use 6 - 8 times less concrete than a slab, meaning I can mix it myself (once I figure out a way to get the cement mixer down the side of the house...).

Will you be documenting the build process? I for one would be really keen to see how you do it/what you learn as I'll be considering something similar this/next year.

Edit: @Hovis this is amazing!

Ah yes I forgot you were going down the form route. I guess the main thing would be your soil condition. If you can get them down to clay they should be rock solid. I'm guessing 12 piles will be 2m spacing?

I'd caution against mixing yourself it's a horrible job, can be difficult to get the mix right even using pre-mix 50N bags, and will fuck the cement mixer.

Much better to get in one of the mobile batching plants on the back of a wagon as you won't need to do volumetric calcs for ordering and you only pay for what you use. They can pump it a limited distance although barrowing further will be a pain.

This is super.

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i keep coming back to this thread, especially at this time. i also took the time to watch ali dymock's build diary on YT. i didn't realise how much you picked up off him, hovis ;) His tips are fantastic but f*ck me his taste in music is shocking.

For my own build, which is likely to be 5 years down the line, i'm thinking concrete slab (i intend to have a large metal lathe in there), a few courses of brick or block, then timber. Not really sure why I'm leaning towards having brickwork. This account mentions that it's easier to get them level for your bottom plate, for example.

I could watch this stuff all day...thanks for sharing.