Workshop: Advice wanted, and very much needed!

[Omnibuswoman]

 

 

Our builder was going to build our workshop for us, but is now too busy and I have decided to crack on and do it myself. I have never done anything even remotely as challenging as this - putting up shelves has been the limit of my previous DIY experience - so I am quite apprehensive. HWMBO and my son have been roped in to help, and my dad will also come along to tell me what I’m doing wrong ?...

 

The builder has laid a reinforced concrete base, and two rows of breeze blocks around three sides as follows...

 

I will build stud walls (2x4s at 600mm centres) up to a total height of 2.4m. First question: how do I fix the wood frame to the block wall?

 

I was planning to build up the wall by facing it with 9mm OSB boards, then a waterproof membrane, battens, and finally shiplap cladding. The builder has advised me to put the OSB on the inside of the wall, not the outside, then to batten a membrane to the stud wall and clad on top of that. Second question: what are the advantages and disadvantages of each method? Is one better than the other? We may put insulation into the wall at this point (something wooly) or wait until the house is insulated with blown cellulose an insulate it with that.

 

The roof will be a gently sloping apex roof (12 degrees), with a central beam and rafters, strengthened with a cross brace. I planned to put OSB on top, followed by corrugated roofing sheets, but I can’t see how I will close the gap between the top of the rafters and the top of the walls. Question three: Should I put the OSB on the inside of the ceiling instead, and then fix the roofing sheets to the top of the rafters??

 

I have been offered some second hand windows for it, and I think I have worked out how to build the frames for the windows, and plan to put in both large double doors at the front and a small door near the back for quick access to the freezer. Does anybody have any tips or tricks for framing and fitting windows and doors??

 

Any and all advice and encouragement gratefully received!!

 

 

 

 

 

[Jilly]

Wow, nothing but encouragement to offer here! My builder has gone AWOL too, and I'm seriously considering pushing myself too.

[Marvin]

If you build it like my shed then stainless steel screws every 600mm through bottom bit of wood into rawplug or easier a hammerfix!

 

Make 1st coat after battening vapour barrier ( to let moisture out but not in) 

 

Make sure external cladding hangs below documents or it will drip into the workshop.

[Onoff]

Presumably there's no damp proof membrane under the slab? You'll need one under the "floor" which I would also insulate.

 

What are the "concrete blocks", lightweight Celcon types or "dense" ones. Any idea of the kN rating of the blocks?

 

You could drill down through the sole plate of the stud walls and resin anchor into the blocks (a lot less stressful on the blocks) or even run some stainless steel builders banding down the inside face of the stud walls and screw to the concrete slab.

[Marvin]

After the stud plastic sheeting to stop moisture getting in the wall. 

If its a workshop light OSB if yournot going to hang anything on the walls or 12mm thick osb if you are. Remember to protect any electric cables from the insulation if they are in the walls.

Onoff also has great ideas and I'm sure will come up with other/better ideas.

 

Good luck

 

M

[Tennentslager]

44 minutes ago, Omnibuswoman said:

 

 

Our builder was going to build our workshop for us, but is now too busy and I have decided to crack on and do it myself. I have never done anything even remotely as challenging as this - putting up shelves has been the limit of my previous DIY experience - so I am quite apprehensive. HWMBO and my son have been roped in to help, and my dad will also come along to tell me what I’m doing wrong ?...

 

The builder has laid a reinforced concrete base, and two rows of breeze blocks around three sides as follows...

 

I will build stud walls (2x4s at 600mm centres) up to a total height of 2.4m. First question: how do I fix the wood frame to the block wall?

Damp proof underneath and just lay them on top. You can fit steel restraining straps afterwards.

 

I was planning to build up the wall by facing it with 9mm OSB boards, then a waterproof membrane, battens, and finally shiplap cladding. The builder has advised me to put the OSB on the inside of the wall, not the outside, then to batten a membrane to the stud wall and clad on top of that. Second question: what are the advantages and disadvantages of each method? Is one better than the other? We may put insulation into the wall at this point (something wooly) or wait until the house is insulated with blown cellulose an insulate it with that.

Inside means you have a finished surface inside. OSB provides racking strength, it makes the building stiff and rigid. Put rockwool in the spaces between the framing outside and then membrane and battens. This is how I did mine, look up my blog for photos.

 

The roof will be a gently sloping apex roof (12 degrees), with a central beam and rafters, strengthened with a cross brace. I planned to put OSB on top, followed by corrugated roofing sheets, but I can’t see how I will close the gap between the top of the rafters and the top of the walls. Question three: Should I put the OSB on the inside of the ceiling instead, and then fix the roofing sheets to the top of the rafters??

I would put the OSB out side as you can fix the roofing sheets to it. Insulate inside and line with plasterboard or pine tongue and groove

 

 

I have been offered some second hand windows for it, and I think I have worked out how to build the frames for the windows, and plan to put in both large double doors at the front and a small door near the back for quick access to the freezer. Does anybody have any tips or tricks for framing and fitting windows and doors??

Leave 5mm on each side of the window/door dimensions in the frame.

 

Any and all advice and encouragement gratefully received!!

Enjoy yourself, it should be fun!

 

 

 

 

 

 

 

[Tennentslager]

Blog entry with photos here

 

[Onoff]

4 minutes ago, Marvin said:

Onoff also has great ideas and I'm sure will come up with other/better ideas.

 

 

Her's will be built and mine will still be on the drawing board!

 

 

 

[Marvin]

 

4 minutes ago, Onoff said:

 

Her's will be built and mine will still be on the drawing board!

 

 

 

Yes but at least you had a cunning plan!

[ToughButterCup]

1 hour ago, Omnibuswoman said:

...

First question: how do I fix the wood frame to the block wall?

 

Here is a list of vidoes which might well help you  Framing a block wall

 

1 hour ago, Omnibuswoman said:

...

Second question: what are the advantages and disadvantages of each method? Is one better than the other? We may put insulation into the wall at this point (something wooly) or wait until the house is insulated with blown cellulose an insulate it with that.

...

 

This video should help  with that issue

 

1 hour ago, Omnibuswoman said:

...

Question three: Should I put the OSB on the inside of the ceiling instead, and then fix the roofing sheets to the top of the rafters??

...

 

Its more complex than that. This is the video, one of a series which covers your questions

Door framing's not so complex.... but its nitty gritty

 

YooChoob's your friend.

Good luck.

Ian

Edited May 8, 2021 by ToughButterCup

[Onoff]

1 minute ago, Marvin said:

 

Yes but at least you had a cunning plan!

 

HAVE!

 

 

 

 

[Marvin]

Green and purple! ????

[Ferdinand]

37 minutes ago, Tennentslager said:

Blog entry with photos here

 

 

I think you can just cut and paste them.

 

ie mouse select several, then CTRL-C CTRL-V (in Windows).

F

[Ferdinand]

Remember that you need to consider ventilation as well as insulation,

[Omnibuswoman]

Thank you all for your replies. Such a huge encouragement and brilliantly useful info. 
 

The concrete slab has a DPM /radon barrier under it as we’re in radioactive Cornwall ☢️, but I will also put a membrane under the sole plate and will take the cladding down over it. 
 

I’ll post some pics and words as I go along. And will do my best to enjoy the process!! ☺️

[ToughButterCup]

10 hours ago, Omnibuswoman said:

...

I’ll post some pics and words as I go along. And will do my best to enjoy the process!! ☺️

That's the only way. 

 

JustBloodyDoIt - habit forming,  wholesome, frightening. Satisfying. 

[SteamyTea]

16 hours ago, Omnibuswoman said:

First question: how do I fix the wood frame to the block wall

With something like this.  Drill a hole and hammer them in.

https://www.screwfix.com/p/fischer-nylon-hammerfix-8-x-100mm-50-pack/33940

 

15 hours ago, Tennentslager said:

what are the advantages and disadvantages of each method? Is one better than the other

It is to do with breathability and condensation risk.  After the vapour control layer (polythene sheet on the inside), you are looking to allow any vapour to travel outwards in a heated/occupied building.  So as you travel outwards, it is easier for water vapour to travel and be evaporated (evaporation is a combination of humidity differences, temperature and airspeed).  To put a sexist slant on it think of drying washing.  If you lay a wet towel on a floor, the part touching the floor does not dry, but the part exposed to the air does, this is why we hang washing on a line (not really sexist as I do all the washing here).

15 hours ago, Tennentslager said:

Should I put the OSB on the inside of the ceiling instead, and then fix the roofing sheets to the top of the rafters

This is all about detailing.  You could probably do it either way.  Fitting the OSB on the outside is probably easier when it comes to fitting the insulation but you will be cutting up a lot of small sections of OSB to fil the gaps between the walls and the roof.  Not hard, just fiddly and boring.  If you fit it with screws, rather than nails, you can easily change it if it all goes wrong.

Nothing to stop you from doing both in reality.

15 hours ago, Tennentslager said:

Does anybody have any tips or tricks for framing and fitting windows and doors

Make sure the aperture studwork is solid, square and true.  And the right size.

 

Remember, it is a posh shed, not a forever home.

If you were in West Cornwall, I would come over and have a laugh.

 

What power tools do you have, a cut off saw will be useful, as would a planer thicknesser.  And a decent table to work on.

Edited May 9, 2021 by SteamyTea

[SimonD]

18 hours ago, Omnibuswoman said:

 First question: how do I fix the wood frame to the block wall?

 

Tapcon screws are good for this. For your timbers you'd need the 82mm length: See https://www.metrofixings.co.uk/main/product/productinfo/606/5 x 82mm 3F82 Countersunk Concrete Screw/1

Installed at 400 centres should work fine. You just drill a hole, clean out the hole and screw them in.

 

For belt and braces you could add some straps.

 

18 hours ago, Omnibuswoman said:

I was planning to build up the wall by facing it with 9mm OSB boards, then a waterproof membrane, battens, and finally shiplap cladding. The builder has advised me to put the OSB on the inside of the wall, not the outside, then to batten a membrane to the stud wall and clad on top of that. Second question: what are the advantages and disadvantages of each method? Is one better than the other? We may put insulation into the wall at this point (something wooly) or wait until the house is insulated with blown cellulose an insulate it with that.

 

The first method you mention is the traditional way of building modern stick timber frames. Frankly for a workshop, I don't think it matters that much. However, if it's going to be insulated and possibly heated then with the OSB on the inside, this creates your vapour control layer (providing you tape all the junctions and corners between the sheets) that prevents too much moisture entering the frame from the inside of the building. Then, as your builder has said, you just need a breather membrane to the outside. If you go for the osb around the outside, you'll need a vapour control layer - anything from a thin plastic sheet to advanced adaptable membranes - in the inside of the frame. You'll also need a breather membrane on the outside of the osb. So in a way, osb on the inside can be easier.

 

If you're planning to insulate and have it heated, especially with blown cellulose, you need to get the detailing right on the wall buildup to take the pressure of the pumped insulation, but the osb on the inside should be fine.

 

I'd also suggest that if it's to be heated and you insulate with something wooly, I'd counter batten the outisde of the frame with 2x2 and install an extra layer of insulation. Using cheapo glass wool insulation this will be as cheap as chips. It'll take the edge off the cold on winter and help a bit in the summer. So basically you'd end up with a wall build up from the inside:

 

osb
stud wall
2x2 cross battens

breather membrane

battens for cladding

cladding.

 

18 hours ago, Omnibuswoman said:

The roof will be a gently sloping apex roof (12 degrees), with a central beam and rafters, strengthened with a cross brace. I planned to put OSB on top, followed by corrugated roofing sheets, but I can’t see how I will close the gap between the top of the rafters and the top of the walls. Question three: Should I put the OSB on the inside of the ceiling instead, and then fix the roofing sheets to the top of the rafters??

 

I would line the inside of the roof structure with osb - to act as your vapour barrier, just like with the walls. With the metal roofing sheets you are going to get condensation on the inside. You must make sure you have a ventilation gap between your insulation and the metal roof. So I'd recommend you plan in battens on top of the rafters. With or without insulation, I'd install a breather membrane on top of your rafters, under the battens. Essentially you'd end up with a buildup along these lines from the inside:

 

osb
rafters (with insulation)

breather membrane
battens (forming ventilation gap)
roof sheet

 

As with the walls, it's worth considering the thickness of your rafters and the amount of insulation you can get in there.

 

18 hours ago, Omnibuswoman said:

Does anybody have any tips or tricks for framing and fitting windows and doors??

 

Just make sure your rough opening are straight and true, ? and a bit larger than your windows and doors. 10mm each side/top & bottom usually works fine. There are plenty of sites that'll show you how to frame rough openings but here is one that covers it https://www.jlconline.com/training-the-trades/framing-rough-openings_o

 

The great thing about timber framing is that you can actually still do most of it with hand tools. All you really need is:

 

Hammer
Screwdriver
Hand saw

Pencil
Tape measure
Square (speed square is ideal)
Spirit level
Chisel
(Stapler for membrane helps)

String (for straightening frame and walls)

 

But you'll need a drill for your sole plate and anchors..

 

Good luck with it!
 

Edited May 9, 2021 by SimonD

[SimonD]

17 hours ago, ToughButterCup said:

This video should help  with that issue

 

Interesting video. At about 5:50 there's a picture of the stud wall with an octo-stud arrangement! It looks like some of the studs are sistered but surely the timber frame company could have found a more efficient solution?

[SteamyTea]

1 hour ago, SimonD said:

Interesting video

Interesting in that they did not fully tape the joints on the insulation.  So air can travel possibly from outside to inside.  Though with the OSB on the outside this is much reduced.

[SimonD]

7 hours ago, SteamyTea said:

Interesting in that they did not fully tape the joints on the insulation.  So air can travel possibly from outside to inside.  Though with the OSB on the outside this is much reduced.

 

I missed that. Yes, not great. I've come across uk framers who believe that if you tape the insulation joints you don't need a vcl - I've also seen it approved by building control.

[SteamyTea]

11 minutes ago, SimonD said:

I've come across uk framers who believe that if you tape the insulation joints you don't need a vcl

I have heard that as well.

I can understand it if it is a single sheet, bonded at the sides.

But then I have never seen a sheet that does not have a few holes in it.

A sheet of polythene is pretty cheap to buy and installing is only a matter of not being a bad tempered knob on a fixed price, and who does not understand why it is there.

So that will be most builders over 35 years of age, or stones, makes no difference.

[ProDave]

21 minutes ago, SteamyTea said:

I have heard that as well.

I can understand it if it is a single sheet, bonded at the sides.

But then I have never seen a sheet that does not have a few holes in it.

A sheet of polythene is pretty cheap to buy and installing is only a matter of not being a bad tempered knob on a fixed price, and who does not understand why it is there.

So that will be most builders over 35 years of age, or stones, makes no difference.

So what will happen with no VCL?

 

I regularly work on 50 year old timber frame houses with plasterboard (not even foil backed) straight onto the timber frame, and I have yet to find one with problems.

[Roundtuit]

1 hour ago, ProDave said:

So what will happen with no VCL?

 

I regularly work on 50 year old timber frame houses with plasterboard (not even foil backed) straight onto the timber frame, and I have yet to find one with problems.

 

Just guessing, but maybe older structures with poor insulation allow enough heat loss to keep moisture moving in the right direction.  Isn't there some calculation to be done to take wall build-up and dew point into account?

[SteamyTea]

9 hours ago, ProDave said:

So what will happen with no VCL?

 

I regularly work on 50 year old timber frame houses with plasterboard (not even foil backed) straight onto the timber frame, and I have yet to find one with problems.

@Roundtuit sums it us nicely.