Dom's workshop build

[DomD]

You'll find that eaves closer difficult, and it doesn't provide anywhere for the top of the boarding to finish against. Take a look at my workshop build thread at The Woodhaven 2 to see photos of an easier and neater approach.

I have had a look and will switch over to that - looks simpler to execute too. Are those 22x150s against 50x100s? What boarding are you referring to? - as I plan to have exposed rafter tails.
EDIT: after further analysis they appear to be 50x50s and 50x150s

Other than that do you think the voids etc look reasonable and work with the metal box section roof?

Sorry for all the questions

Thanks

 

[DomD]

All walls up - I nailed the last in too soon and ended up having to use a hacksaw to cut through them to readjust to level.
Double top plate is also on, this is the state it will be left in for ~1week as I go to Scotland. Roof on when I return.
The walls are parallel ±10mm so fairly good I think.

 

[DomD]

As far as loft insulation and wall insulation, is it just cheapest mineral wool with the required thickness? I will be using cavity batts in walls and roll insulation between rafters.

Do I completely fill the rafters leaving no gap between the membrane and insulation or should I get thinner insulation to allow the membrane to sag?

Thanks, Dom

 

[MikeG.]

The membrane should sag. Mineral wool is fine for both.

 

[DomD]

Will that require thinner roll insulation (e.g. 100mm) between the 150mm rafters?
Thanks

 

[Woody2Shoes]

Will that require thinner roll insulation (e.g. 100mm) between the 150mm rafters?
Thanks

Yes - normally you'd expect an air gap of about 50mm. Exciting to see progress, cheers, W2S

 

[MikeG.]

Yes. I would allow a 25mm sag, min, so if you can get 120/ 125 thick insulation, then use that. Otherwise, 100mm. You could push 25mm of Celotex into place above 100mm of mineral wool.

 

[DomD]

Thanks both of you, I think from my limited research the larger 50mm gap is for vapour impermeable felt and a breather membrane only requires min 10mm. I will see where I can find 125mm loft roll insulation.
I'm also going to try and use a higher quality membrane on the walls as I may need to leave it unclad for some time.

 

[Woody2Shoes]

Thanks both of you, I think from my limited research the larger 50mm gap is for vapour impermeable felt and a breather membrane only requires min 10mm. I will see where I can find 125mm loft roll insulation.
I'm also going to try and use a higher quality membrane on the walls as I may need to leave it unclad for some time.

I think that it's worth following the manufacturers instructions for the particular membrane/underlay you actually buy (if you're lucky, on the label, otherwise on the website). My experience is that they all (perhaps excluding the old-fashioned tar-based felts) shrink to a greater or lesser degree. Cheers, W2S

PS re. unclad walls - the main enemy of the membrane is UV light - a good way to temporarily protect whatever you go with is to cover it with black DPM sheet held on with battens

 

[DomD]

PS re. unclad walls - the main enemy of the membrane is UV light - a good way to temporarily protect whatever you go with is to cover it with black DPM sheet held on with battens

I've got spare dpm so will look at using it for that. Any recommendations for the membranes for walls and roof? I was looking at the novia ones as they are fairly low cost.

Ridge supports up now. I plan to lift the ridge beam into space tommorow.

 

[DomD]

As I have decided not to do raised ties but regular joists sitting on the top plate, does it make sense to do them first?

 

[MikeG.]

There are arguments either way. You could do the joists first and put down some temporary boarding on them to enable easier access to the ridge, then do the ridge, then the rafters. However, you'd have to fix battens etc to the joists such that they were safe from falling over. Or you could do it the orthodox way.........rafters first.

 

[DomD]

There are arguments either way. You could do the joists first and put down some temporary boarding on them to enable easier access to the ridge, then do the ridge, then the rafters. However, you'd have to fix battens etc to the joists such that they were safe from falling over. Or you could do it the orthodox way.........rafters first.

That's what I was thinking with the boarding as I have no scaffold and the top plates are at 2.5m. Why would I need to fix battens if I have nailed down the joists?

 

[MikeG.]

Because tosh nailing doesn't provide much rotational resistance.

 

[DomD]

Ok I will use some battens I have spare.

Another question: you can see the sheathing here is just short of full height:

The osb at the top will cover part of the gap but I was wondering if it would be acceptable to leave ~1" gap at the bottom to be covered by the skirting board - I am assuming the bricks are vapour impermeable anyway so do not need the osb as a vapour barrier?
Also are there advantages to laying two sheets offset horizontally rather than one sheet vertically?

Thanks again for all your help,
Dom

 

[MikeG.]

It's fine to leave a gap at the bottom and cover it later with a board. The problem laying boards landscape rather than portrait is that the horizontal join might be unsupported (ie no timber behind it). If you've got noggins around the building at the right height then fine, it makes no difference at all.

I don't know if your straps are fixed in place yet, but if they aren't, see if you can move them away from the edges of blocks. They're stronger if they are at least 3 or 4 inches in from the edge of a block.

 

[DomD]

It's fine to leave a gap at the bottom and cover it later with a board. The problem laying boards landscape rather than portrait is that the horizontal join might be unsupported (ie no timber behind it). If you've got noggins around the building at the right height then fine, it makes no difference at all.

I don't know if your straps are fixed in place yet, but if they aren't, see if you can move them away from the edges of blocks. They're stronger if they are at least 3 or 4 inches in from the edge of a block.

That makes sense - I'll do vertical then.
Already screwed down unfortunately but quite a few are away from edges and I did a fair amount more than recommended on your diagram.

Currently on the joists putting in the ridge - you can see the gap of three joists:

Dom

 

[DomD]

Ridge up! Unfortunately it is fairly bowed with a 4cm difference from eaves to ridge at opposite sides - I suppose I just put the rafters on the short side in first to push it into place?

Regarding rafters, is the best way to cut them just with a circular saw and is there any way to get around having to lift the guard manually when making the seat cut? Should the rafter tail be cut afterwards?

Thanks

 

[MikeG.]

Put the rafters up in pairs, and tap the high one down. They'll soon pull the ridge straight. You will probably find it easiest to use both a circular saw and a hand saw for cutting the rafters. Clearly mark your pattern piece, and wear goggles, because precision circular sawing involves looking at the blade, not the mark on the base, and that means getting a face-full of sawdust.

 

[DomD]

Half of the rafters are now up:

I cut them by lifting them onto my saw horses cutting one of the angled sides with my mitre saw and doing the rest with a circular saw. My circular sawing certainly could use some improvement but I think the birdsmouths look reasonable:

The nailing schedule I have used for the roof is:
Joists to top plates: 4x 3.1in toenails
Rafters to top plates 3x 3.1in toenails
Rafters to joists: 3x 3.1in face nails
Rafters to ridge: 3x 3.1in face nails

There is lots of space in the 'attic' area for storage - I'm glad I didn't raise the ties.

Dom