Building the new workshop ... may have light at the end of the tunnel!

[LizBurg]

Next step was making everything if not watertight then at least better protected against the near continuous stream of water falling out of the sky, or so it seemed.

Now that is in two parts, the roof and the walls - I know, blinding flash of the blinking obvious there! But having said that the essential difference between the two is the insulation. I hope to be spending a considerable amount of time in the workshop including in the colder months (not least because at the moment I have a seasonal summer job that I enjoy a lot but less secure employment during the winter months) and I want to keep heating costs down. Plus of course, although the obvious solution to heating is just a small fan heater from Screwfix put on for a quick blast in the morning when I go out to the workshop that means the machine tools and unfinished workpieces will be in an unheated environment with the potential for condensation and worst case rust issues. So insulation in the roof above the OSB sheeting, and insulation in the walls inside the sheeting in the space between the 2x4s (plus a bit more but I will get to that.)

Basic warm roof - from the inside out , roofing layer of OSB as last time, thermal vapour barrier, 25mm PIR foam, second layer of OSB, then an extra layer to protect the OSB and act as underfelt and finally, a bit of an extragavance I admit, asphalt shingles. Roofing felt would have done an equally good job but I prefer the look of the shingles and they should last a lot longer than basic felting. The roof slope is right at the bounds for the use of shingles though but with a bit of extra care I think it should be OK, I guess time will tell.

Ideally the roof insulation should be thicker than 25mm but being limited by the standard height restriction of 2.5m 25mm of PIR foam is the maximum usable. Should it turn out to be inadequate then in the future extra insulation can be fitted inside between the rafters.

The other consideration is of course light. The workshop basically runs east west (long axis) with the double doors at the east end and the side door in the south side. I want, well given the size of the workshop need, solid walls for storage cupboards, racking etc so the roof will be the major source of natural light, with maybe a few small windows in the doors eventually. The issue then becomes not just potential heat loss through the roof windows but also potential solar gain in summer through the south facing side of the roof. Also as far as possible it's easier building to have equal roof thickness on both the north and south faces of the roof. Hence solid roof as described above on the south facing side and at the end bays between the end pair of rafters with 35mm multiwall polycarbonate for the rest of the roof on the .north facing side.

Roofing started with reflective thermal vapour barrier first (Superfoil SFTV) and 25mm edging strip round the roof to keep the PIR foam in place. And before anyone asks yes, I did put extra 2x4s inside as supports for the main roof beam whilst working on the roof. I'm not that .... (fill in the blank for yourself).

Then the outside layer of OSB on top, through screwed into the rafters inside

Do all the south facing roof then cover with waterproof shield barrier and start shingling. Of course the shingles only cover the upward facing part of the roof so to give decent edge protection I started with a narrow strip of felt roof edging strip just to wrap round the roof edge and return under the outside eaves, not only creating a waterproof edge but also giving a drip edge. It also obviated the need for a layer of cut off shingles at the bottom edge of the roof.

Doing the actual shingling really wasn't that bad I found, just a question of taking care to keep the line straight and working systematically on both the south face and the end parts of the north facing roof.

On the north, windowed side of the roof to equalise the thickness meant first cutting strips of spare OSB to go on the top of the rafters, then fitting the seals for the glazing on top of that. Having not done this sort of thing before I took the advice of the supplier about the overlap on the rafters needed and had the polycarbonate sheets supplied cut to size. Additionally having them pre-cut to size meant they came with waterproof tape at the top end and breatable tape at the lower end pre-installed. Much easier than cutting them myself and not much extra cost. If you look closely you can see the OSB strip under the seal. Note also that at the far end of the roof the end bay already has the same build up as the other side except for the shingling

The roof glazing panels were installed from inside the workshop just lifting them through and laying them in place then using the top glazing bar with the appropriate seal screwed through into the rafter to hold everything in place. Getting glazing bars suitable for 35mm multiwall sheeting did take a bit of searching online, the typical snap in plastic glazing bars don't come in the thicker spec so it had to be metal strip with rubber edge seals fitted screwed through with a dab of silicone sealant on the screws and then caps tapped in place to cover the screws.

The top seals which lie under the glazing bars create the necessary waterproofing between the roof lights and building up the end bays to the stage of having the outer membrane covering on but not shingled gave a plain smooth surface for the seals on the glazing bars to mate to avoiding gaps which could allow water in. I admit to running a bead of flexible silicone down the outer edge as belt and braces insurance though Along the top edge of the glazing, to ensure a waterproof seal preventing water penetration between the top of the glazing and the roof ridge I ran a strip of self adhesive lead flashing. A bit of a pain in the neck getting it to seal but a seam roller for wallpaper helped a lot getting it rolled down flat - tip, don't do it cold, it gets much more flexible warm. Then it was simply a question of shingling the end bays.

Shingling all the way to the apex of the roof just left a slightly overlapping seam of shingles to be covered with a strip of roofing felt and all joins are covered. Again, as belt and braces against capillary action under the shingles and wind damage I also tacked the edges of the shingles down with felt roofing adhesive as I went along.

And since there is a nice strip of felt along the ridge, why resist a bit of a decorative touch at the ends? The excess shingles sticking out a bit on the left I later trimmed with a knife.

And after all that, I think it turned out pretty well, many thanks to my assistant, and since then, it has turned out to be waterproof and let's plenty of even light in.

Outside of the walls next, a lot simpler, well, to begin with .... but next time

 

[flying haggis]

I personally would have put a lot more nails in that felt ridge strip to stop the wind and water getting under it.

 

[Fergie 307]

Or use the onduline verge pieces, very good for this sort of thing. To be fair felt would work, but I would use plenty of adhesive.

 

[Fergie 307]

Only observations would be why the doubled up top on the wall? Not clear how big the building is, but I would just use a single 4x2 the whole length. Plenty strong enough.

Where the joists attach to the top of the wall it is potentially much easier, and stronger, to mount them using vertical screws up through the top of the wall and into the joist. 6mm wafer heads is what I have used. Same for any cross braces, and to secure the cross braces to the joists.

I do wonder a little about the ridge beam. With such a shallow pitch I would have thought a deeper beam with greater intrinsic strength?
I know you are intending to add side to side braces, but would still be concerned about that sagging over time.

My recent build, very similar construction, is 4.8m long by 3.6m wide. It has a similar roof pitch. I have used a single 8x2 as the ridge beam, with 4x2 joists. 8x2 over the top I know, just that I had a couple of 4.8m lengths from a previous job so used one of them, rather than buying something specific.
My ridge beam is bolted to welded steel brackets bolted through the top plates of the end walls. Only place I have doubled up the top plate is at the front, where the beam sits directly over the 1.2m door opening. There I have fitted a pair of 6x2 vertically under the top plate between the door uprights. At the other end the beam sits directly over one of the wall uprights.

For securing the frames to the base I used to use resin mounted studs as you have done. Now changed to concrete bolts, the type that screw directly into the concrete so no expansion. They are brilliant.

Don't know what you are proposing to line it with. I have always used the water resistant t&g chipboard flooring. Laid horizontally and staggered like bricks. Gives a nice smooth wall, and quite a bit cheaper than OSB or ply.

Know what you mean with the bike lift. I have a scissor one. When not in use I stand it up against the wall, secured with some big hooks and a chain. Much nicer to have a flush one in the floor.

MZ fan here too, have had loads of them. Currently got an ETZ 125 and a 251 Saxon.

 

[LizBurg]

Hi there folks,

Good points about both the nails and the adhesive on the ridge felt. It does actually have adhesive run along the length of it to help keep it down, If I get a problem with it I will take a look at the Onduline ridge . The biggest difference is that doing it with roofing felt means the entire ridge cover has no seams in it as the piece is cut full length from a 10m roll I had.

Sag? I agree with what you say I'll hope for now that with cross braces internally it should be OK, or triangular ply fillets to tie/brace the beams.. The most problematic bit will be the double doors but my intention is a removable central strut which will act as a brace normally and the two doors will each meet that in the middle, either can be opened independently or open both and remove the strut for (probably rare) full width access.

I thought about chipboard and ply for the reasons you say and agree it's a good way to do it but locally per square metre OSB is cheaper than chipboard. (I get stuff at Selco, mainly because of the good (free) delivery service. If I could get the moisture resistant chipboard cheaper than OSB I might well have gobne with that. But, otoh, I do kind f like the slightly rough look of the OSB ;-)

MZs? My first bike was an MZ ETS 250 Trophy Sport, I know, a 250cc as a first bike on a provisional licence - that dates me! But it was a brilliant bike and I used to love the double takes I got filling it with fuel when they saw 4 gallons on the pump! (For non-bikers, that's a BIG fuel tank for a 250cc bike) And it had the fuel tank cap with the ISDT championship dates on it. (It got stolen and all the police ever recovered was the frame and a bent silencer) The two MZs I have waiting to be rebuilt are however, those rarest and most heretical of MZ creations, a pair of 4-stroke SM 125s. One is not even registered with the DVLA, so to get the age appropriate plate I plan to rebuild that one to proper SM spec, but I am toying with the idea of rebuilding the other to SX spec as a form of ultra-lightweight adventurey/trailey sort of bike. That's why I think the 125SM might be a good basis, the standard fuel tank is good for 200 miles on road. My backpacking gear is all very lightweight so maybe a couple of tanks, one each side for spare fuel and emergency spares, camping gear across them and a MUCH more comfortable seat for long distances at a suitably relaxed pace and without the hernia induced by picking up a 1200cc BMW after dropping it off road.

 

[Fergie 307]

The one I always craved was the BK350. Maybe when I retire

 

[LizBurg]

Hi everybody,

My apologies for the delay in continuing the saga! Last time roof was on and to my immense gratification and with no small amount of good fortune it has turned out to be completely watertight. I am also glad to say that after a few storms it remains in place and is still watertight, as it should be. I would have been really miffed at myself if it were not. Next bit is external protection for the walls which, after getting the roof sorted, were still bare OSB.

Now, that's in two steps; short term protection followed by longer term protection. In the very short term I slapped on a couple of coats of a water repellent mould resistant wood treatment. I used Barrettine wood treatment which I got from Toolstation on the basis that it gave good coverage with little hassle. Turned the OSB quite a nice shade as well as it turned out. Now that is short term only but having done that the excess DPM all round the base could then be rolled up the walls and taped and stapled to the walls to provide a high bathtub effect, about 600mm above ground level.

Of course, left like that would mean rain would trickle down the walls and behind the DPM, which would make it all rather pointless so the next stage was a breathable waterproof membrane wrapping the whole shed, suitably overlapping both the DPM at the bottom and itself being overlapped so rain trickling down the upper layer would run over the lower layer, thus all water hitting the sides would run down reaching ground outside the DPM to drain away into ground. This could be stapled directly to the OSB as both the longer term breathable membrane for the workshop and a short term weather protection for the OSB during building.

(Hindsight alert) This is the stage where you need to work out what holes you need in the walls for ventilation so you can cut the holes and get vents installed over them. Plan is passive vents at the double door end of the workshop either side of the doors and a middle vent in the opposite end of the workshop to take an exhaust fan so that fumes etc can be vented if required. But since I forgot at that time I had to do them later when it was a bit more awkward, ho hum. Also notice that there is still quite a decent gap between the dug out ground level and the bottom of the membrane which is at the level of the top of the concrete slab, in due course this will be much less. But a certain amount of gap will be needed to stop the bottom of the wall getting soaked by rain splash off the ground.

Now, where was I, oh yes, next is back to the central idea, the workshop is intended to be somewhere I can be in any weather and that will hopefully outlast me as I want to spend the next 15-20 years working IN the workshop not forever working ON the workshop - even if it feels like the latter at the moment. That means outside cladding and here I confess going for a, I hope, quality offering.

Cladding requirements are it should (a) last in any weather for at least 15 years with minimal maintenance, (b) be reasonably easy to handle and fix to the walls and (c) look good. Folks might vary on the importance of the last one but I shall be looking at the workshop wherever I am in the back garden and I don't want to annoy the neighbours with an eyesore. And I will admit I do have something of a liking for the New England style of buildings

So (now I have got my excuses for what some will consider extragavance in first!) I went with fibre-cement board, Hardie Plank to be specific. To be even more specific in the Woodland Cream finish. The advantage of the pre-painted boards is kind of obvious from the phrase 'pre-painted' I assume, although having said that the board ends and any cut edges of the board do need sealing with the same colour paint which comes from the same supplier. I did use their sample offer to get a couple of colours to look at (the other being Sage Green) but both my partner and I were happy to go with the cream.

There are though two corner choices, either thicker fibre cement boards which you form the corner out of or aluminium corner mouldings. My first thought was to go with the easier aluminium but when I went to my local supplier and could see the alternatives in the flesh I preferred the wider fibre cement edges. Delivery from the local supplier (UP Building Products in Maidenhead was first class including helping us carry it all through to the back of the house and get it properly stacked without damage. The boards need to be carried on edge rather than flat as they are so flexible in that direction it can crack the paint finish if you are not careful or in extremis crack the plank itself.)

The way the system works is straightforward, you have vertical battens on the walls (pressure treated ) and nail the planks horizontally from the bottom up overlapping as you go by a minimum of 30mm so the180mm wide boards give you 150mm cover at each run. At the bottom you start by using a perforated aluminium strip attached to the vertical battens which allows air in behind the cladding. keeps critters out of the space and creates the correct standout for the bottom row of planks. A small breather gap is left at the top, again closed with a perforated aluminium strip. Specification is for a minimum air gap of 20mm, 25mm preferred. My advice now would be go with the 25mm, cutting the aluminium strips down to a smaller width is a pain in the proverbial, easy enough with an angle grinder but still a pain.

The system therefore from the inside out is wall covered with breathable membrane, air gap from the vertical battens spacing the cladding away from the wall, cladding acting both as an outer weather protective layer and as a rain shield protecting the waterproof breathable membrane from damage from the elements whilst the ventilation gap keeps the wall itself dry and the ventilation also means any water vapour coming through the walls from inside gets vented and doesn't build up any damp spots.

So, we can see the vertical battens fixed to the walls and the aluminium strip across the top of the battens. Note also that the previously uncovered eaves are partially closed in..

The edge strips are nailed together to form the corners which are then nailed to the walls. second fix 18G nails using Silverline air powered nail gun if anyone is interested. Depth of penetration has to be watched but can be varied by varying the air pressure, test on a spare piece first!.

Corners are fixed to the walls and then the planks are fixed from top to bottom. Note the use of Gecko clamps which I was able to borrow from a work colleague (Thanks, Paul) which are absolutely worth their weight in gold - makes it so easy and quick to fix the planks to the wall. Oddly though for the planks the recommendation is a first fix nailer so bigger, heavier than for the battens and corners. The recommendation is for a Paslode nailer which would certainly be easier but it works OK with an air powered nailer, again Silverline, although the consistency of penetration is not as good so occasionally you do need to use a hammer carefully as well just as the tank pressure gets low before the compressor kicks in again to refill the tank.

To cut the boards I got Wen fibre cement shears from the USA via eBay, changed the US plug to a yellow Commando plug (so they can never be accidentally plugged into 230V) and used a rented 110V transformer for power. You can cut the boards transversely using a guillotine type shear a lot more easily and possibly more accurately if you are just planking a straight ended wall and/or only need fairly open angles like 45 or 50 degrees, but since the last top boards had to be cut more lengthwise and/or at a very acute angle I needed something better to cut the plank lengthwise than I could do with a guillotine.

Once you get into the routine it goes up very quickly and satisfyingly! Cut and edge paint some boards, as they are dry mount them to the walls, cut more boards etc. Remember to put the vents in ...

... and finish.

And yes, I think it looks pretty good too, or at least will when the doors are eventually done! Have been drawing some possible designs on the outside to see what will look best.

(Confession, I forgot to take a decent picture after the cladding was finished before the electrics went in, more about what the two cables at the bottom are later ...)

Happy New Year everyone.

 

[Blackswanwood]

Looks smart and it must feel good now the end is in sight.

 

[Jester129]

Very nice Liz! Bet your biceps are bigger than mine after using that nailer, eh?

 

[LizBurg]

Hi Jester,

Don't be so quick to judge me, I got Rachel to do that part of the nailing! What's that old one about 'I love work, I can watch it all day' - wise words to live by ...

More seriously, yes, it is a heavy beast but you get used to it fairly quickly. The harder bits I did were the ones needing to be up a ladder to do the nailing. The second fix gun is much easier to handle. I will say though that for all the grief that some people give Silverline tools, if you want something cheap and cheerful for a relatively small job, they work OK for me. If I were a builder doing this all day every day I would go for better quality. Horses for courses.

The other bit that makes the difference using the gun is if you can support the hose and take the weight of the hose off the gun. ;-)

 

[LizBurg]

Hi Blackswanwood,

Thank you for the comment, it does indeed feel much better, but getting it watertight (mostly) is I think best viewed as analogous to launching a ship*. You've finished the hull but all the internal fitting out is still to do. So the next few posts when they arrive will be the rest that neeeds doing:- internal flooring and heating, wall insulation and wiring, lighting and in due course fitting out.

* But not a submarine of course, they have to be pretty much fully kitted out internally before the pressure hull is finally sealed, so I guess even if I this might be a bit of an attempt at building a flying submarine there are some differences, thank heavens.