bricking up a garage door for workshop, ideas

Martin, if you just have wood, glass fibre then a brick or concrete outer surface, your moisture laden, hot breath will percolate through the wood (joints) and as it gets into the glass fibre, it cools. So at some depth of the glass fibre there is actual water, not a huge amount, but it is a pumping action. The glass fibre is not an insulator now its damp, so the water vapour condenses more readily. Eventually all these drips of water will rot the bottom of the joists, then the internal paneling. . .

***** THE FITTING OF A VAPOUR PROOF MEMBRANE IS A MUST FOR ALL TOP FLOOR CEILINGS OR AT A SECOND BEST, ALI BACKED PLASTERBOARD. ****

I have spoken to builders who have had to replace all the joists on flat roof because of this omission, and speaking to a mate of mine, he has just turned his kitchen extension ceiling from flat to vaulted without a VPM. He is as old as me so it should see out (just?) but its not a job well done. The cost is trivial, its much cheaper then DPM as its much thinner.

Frank

...but you're talking about vapour PROOF, which I understand, but the material in question is vapour PERMEABLE (but waterproof!)

Still not clear to me...

Martin

try this link **LINK**

Bob

Short version for sheds. On inside use everything proof eg plastic sheet. However you must then ventillate or dehumidfy to remove the moisture. If you have a roof that will sweat use an additional breathable but waterproof membrane above the insulation to stop drips sinking into the insulation. Ventillate this space under the roof. Also make sure insulation does not touch the inside of the walls and again ventillate this gap.

Hi Martin,

Different area but Goretex jackets are waterproof but let moisture vapour out (i.e. sweat).

Gary

OK, I get the waterproof but vapour permeable membrane. Maybe the key item is the air gaps - can't see any point in say, outside to inside, wooden wall, vapour permeable membrane, insulation, maybe poly sheet, and then internal wooden wall all sandwiched directly together?

So for my new shed/workshop, currently a shell:
- 20mm T+G (vertical) with external strips over joins for the wall, 2" thick internal bracing horizontal
- 13mm T+G roof with corrugated bitumen tiles, 2" bracing everywhere internally
- 20mm T+G floor on 2" stretchers sitting on slabs with only the corners mortared (so any really wet will fall through the cracks)
- with the slabs spotted onto a concrete base, so there's an escape route for the wet going between the slabs.

...what does the collective think I should have, outside to inside, including air gaps (and how do I get them?), for the walls and ceiling. In simple, unambiguous, words please!

I'm wanting smooth internal walls (WBP ply or ply, preferably, rather than chipboard or OSB) and willing to lose a bit of space by having thicker walls/ceiling.

(...and sorry for the massive thread hijack - will start a new thread if not acceptable)

Martin,

Here's a link to a shed company and their views **LINK**

If it was me and I was insulating a wooden shed then I would do it something like this from outside to inside and if untreated wood, treat the wood on the inside before anything else.

outside wooden wall, air gap 50mm, membrane, insulation 50mm, 1/2" WBP plywood and the same across the ceiling.

You may well need some batten's to space everything but they are cheap enough and you could either use Celotex/Kingspan or my preferred would be Rockwool ProRox SL960 comes in slabs and is very easy to cut with a wood saw. With all the options you will lose some space and will be a bit like a reverse Tardis. If the roof is pitched I would be inclined to fit a vent at the ridge and maybe a couple just above ground level, a small bathroom fan may again be useful in providing ventilation in hot weather or when humidity in the shed is high.

You need to strike a balance with ventilation as the air leaving the building takes heat with it e.g. a shed 6 x 3 x 2.5 with 2 air changes per hour and a temperature differential of say 12 degrees takes about 350 watts of heat with it. I would probably aim at 1 air change/hour and may be use a fan with a humidity sensor.

Others are likely to disagree but my thinking is you do not want a vapour barrier on the walls as this could cause condensation on either side of vapour barrier depending on the temperature differentials and water and wood is not a good thing.

Bob

If you don't want rust you should design for no condensation. To do this the key is ventilation. The building must breathe. Don't make sealed spaces. If you are putting solid insulation on solid walls allow an air gap and ventilate into roof space.

regards Martin

Do not make the mistake of too much ventilation after all it's not a bathroom and all that change of air will need heating in the winter months. From q=m*c*deltaT a shed 3m x 6m x 2.5m with an air change of once per hour then the heat lost from ventilation is about 30watts per hour per degree C so if the outside temp is 0 and internal is 16 then you need to input 480watts.

May be a fan with humidity control on it like this one **LINK** which can be set to start at 60% humidity and off at 50% or a remote switch. On a cold day when you heat the air coming into the shed the relative humidity will drop it is only as the place cools does it go up as the air reaches it's dew point water will drop out.

Bob

I wonder if Bob the Builder cartoon character could do a video on "Bob insulates his shed". Then every kid would know what to do and every parent too as their offspring watched it for the 50th time

At secondary school please write out fifty times:

"A totally water, air, moisture, vapour and bug proof layer must be put on the inside (room side) of the insulation".

A drip proof vapour permeable barrier may be put on the outside of the insulation.

In non-UK climates where airconditionng is used the requirements may be reversed.

Meanwhile I have collected the parts for the heat exchanger for my eventual shed ventillation system. Incoming air through a 12ft x 2in dia aluminium tube ex TV arial support running coaxially down a 4 in plasitic drainpipe which carries the outgoing air. The fan will be throttled to set only a few degrees loss between in and out.going air. This will have valves to shut it off when unoccupied since the aim is such good airtightness that the space can be pressurised.

The more expensive solid insulation like Kingspan and Celotex is 1.5x to 2x better than rockwool.

Use wire mesh over ventillation holes to keep mice and wasps out .

"The more expensive solid insulation like Kingspan and Celotex is 1.5x to 2x better than rockwool."

I had a good friend, Gordon Winstanley, recount one of his tales of a night out on the Town in the early seventies. He was an apprentice on a building site at the time and on the way home after a particularly raucous evening he was staggering past the building site the thought occurred to him that he could get into the stores and lay down for a while "until he felt better".

He woke sometime during next morning on fire. He had made a bed from and curled up in a bed of Rockwool

graham.

Well David

I have been following this thread with increasing dismay!

This must be one of the longest answers ever on how to remove your garage door and convert the space into a workshop! I do hope that you have learned something from it - even if you now think it better that you take up stick wittlin' or embroidery instead of model engineering! However - you are now armed with some information on the delights that await you should you decide to make modifications to your new property which do require the scrutiny of the planning department.

Good Luck!

Norman

"stick wittlin' or embroidery " - Norman, have you any idea how dangerous these pass times are? Health and safety would have you away in double time for messing with sticks (parents don't tell their kids about removing eyes with sharp things for nothing you know).

Mark

Mark

Yes, of course that's true. Do not however discount the dangers of embroidery. My wife is an expert and enthusiastic needlewoman - knitting, sewing, patchwork, quilting, embroidery are all her "thing". When in our house never underestimate the risk of walking across the carpet without your slippers..... and encountering a rogue needle !!!******!!!!

( It's not so much the entry that hurts -- much worse is pulling it out !!)

Norman

Edited By NJH on 23/04/2014 23:53:20

A good few years ago at a world chess championship one competitor fell off his chair and broke his leg. Be warned.

Irrrelevant to the thread, but my worst fear is that some day I'll try to get out of my workshop and find the door bricked from the outside sinse my wife cannot understand how a 73 years old man spends so many hours in this room away from her...................

George