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pre-cased concrete garage
jacko - 27/2/16 at 04:42 PM

Hi all as some of you may have read i am doing up my garage and am going to line it out the thing is what with ?
i was thinking of 6mm plywood or maybe osb paneling and fiber glass behind the paneling
will this be ok in a damp garage
ps i am doing it on the cheap
graham

v8kid - 27/2/16 at 09:40 PM

It depends why the garage is damp. If it is just condensation your plan is sound just add a vapour barrier, on the other hand if penetrating or rising damp the fg will saturate and the framing rot. So fix the damp first.
That's a starter others will chip in.
Cheers!

LBMEFM - 27/2/16 at 10:07 PM

As above, find out the reason for the dampness first. Check that there is nothing like soil or waste laying against the side of the garage or cracked panels or a damaged roof causing the ingress of damp. If it is just condensation as v8kid says just fit a vapour barrier covered with ply.

Sam_68 - 27/2/16 at 10:47 PM

OSB is not terribly resistant to moisture, so I'd use decent quality WBP ply to be on the safe side.

Both plywood and OSB have quite high vapour resistance on their own, though, particularly once painted, and you shouldn't have any major sources of water vapour within a garage, so you shouldn't need a separate vapour barrier. For comparision, it's standard practice only to use a separate vapour barrier with SIPs panels (which have OSB skins) for 'wet' rooms like kitchens and bathrooms, where you're putting a lot of steam into the air.

And I'd use polyisocyanurate rigid foam insulation (ie. Celotex or Kingspan) rather than fibreglass: it costs a bit more, but it's basically twice as thermally efficient, and more importantly, being closed-cell, it won't transmit any moisture that gets in through the cracks in your concrete panels to the internal panelling.

And you won't have a DPC/DPM, so make sure that, at the very least, the plywood lining doesn't contact the concrete floor (use a polythene DPC 'skirt' around the bottom, sandwiched between the ply and the Celotex and tucked out under the end of the ply, to isolate it from the concrete floor, ideally).

coozer - 27/2/16 at 11:05 PM

I run fridge containers and when they are empty and switched off the condensation is horrendous.. Ventilation is the key to get rid of mould and damp... As long as its not rising ground damp.

rusty nuts - 28/2/16 at 08:13 AM

My lock up had a new roof fitted a few years ago , within a week I had mould growing, I put a couple of vents in
the door , one at the top the other at the bottom, result. Check your ventilation

Sam_68 - 28/2/16 at 08:24 AM

quote:
Originally posted by coozer
Ventilation is the key to get rid of mould and damp... As long as its not rising ground damp.


Yep, this is very true - and rising ground damp isn't usually the problem people (usually aftermarket DPC companies!) would have you believe.

Even without a DPM, a concrete floor will only transmit a very modest amount of ground moisture upward. They used to build ships out of concrete, remember - it's actually fairly waterproof!

You still need to make sure your plywood lining doesn't come into direct contact with the floor, though.

hizzi - 28/2/16 at 08:38 AM

i have a concrete section garage that suffered from damp, the roof is profilied sheeting, cement based probably with some asbestos as it was built in the seventies. i put a wood frame and sheeted it with ply over the whole roof then felted with torch on felt, never had an issue since, only ventilation is a poor fitting front door.

coyoteboy - 28/2/16 at 09:51 AM

Yeah I think people don't realise how poorly sealed sectional garage are. It's basically no different to leaving your stuff in a cage with a roof, so everyone says "ventilation is key" when it's not in this case (wind can blow stuff over in my garage it's that well ventilated!). I've had fog *in* my garage.

Seal it properly and then increase ventilation and heat from there. Sure it needs a bit of airflow but first you need to stop the continuous inflow of damp air and outflow of heat.

Sam_68 - 28/2/16 at 10:11 AM

quote:
Originally posted by coyoteboy
Yeah I think people don't realise how poorly sealed sectional garage are. It's basically no different to leaving your stuff in a cage with a roof, so everyone says "ventilation is key" when it's not in this case (wind can blow stuff over in my garage it's that well ventilated!)....

Seal it properly and then increase ventilation and heat from there. Sure it needs a bit of airflow but first you need to stop the continuous inflow of damp air and outflow of heat.


For sure, but PIR insulation is basically draft-proof, if you tape the joints. As is plywood sheathing, come to that.

I'm assuming that draft-proofing will be part of the insulation work. The bigger problem is that they also leak water like a sieve (even the vertical wall panels, if subjected to driven rain), so you need to make sure that water leaking in can'y get to the timber. PIR insulation is your friend here, too, as it is basically waterproof, too.

ianhurley20 - 28/2/16 at 10:31 AM

Seconds and Co are really good for kingspan insulation which is out of spec, perfect for garages
http://www.secondsandco.co.uk/#!shop/ctjy

v8kid - 28/2/16 at 01:28 PM

quote:
Originally posted by Sam_68
OSB is not terribly resistant to moisture, so I'd use decent quality WBP ply to be on the safe side.

Both plywood and OSB have quite high vapour resistance on their own, though, particularly once painted, and you shouldn't have any major sources of water vapour within a garage, so you shouldn't need a separate vapour barrier. For comparision, it's standard practice only to use a separate vapour barrier with SIPs panels (which have OSB skins) for 'wet' rooms like kitchens and bathrooms, where you're putting a lot of steam into the air.

And I'd use polyisocyanurate rigid foam insulation (ie. Celotex or Kingspan) rather than fibreglass: it costs a bit more, but it's basically twice as thermally efficient, and more importantly, being closed-cell, it won't transmit any moisture that gets in through the cracks in your concrete panels to the internal panelling.

And you won't have a DPC/DPM, so make sure that, at the very least, the plywood lining doesn't contact the concrete floor (use a polythene DPC 'skirt' around the bottom, sandwiched between the ply and the Celotex and tucked out under the end of the ply, to isolate it from the concrete floor, ideally).


that's most interesting I would never have guessed that OSB had high vapour resistance I suppost it's because of the layered nature and the glue interleaving.

Cheers!

Sam_68 - 28/2/16 at 01:47 PM

quote:
Originally posted by v8kid
... I would never have guessed that OSB had high vapour resistance I suppose it's because of the layered nature and the glue interleaving.


Yes, the adhesive certainly helps, but at risk of coming across all anorak, there's even more to it than that, too:

Transmission of moisture from vapour can occur in one of two ways:
1) As vapour, in which case the material it's passing through cannot be airtight (which most timber pretty much is, when it's got significant thickness) or;
2) The moisture out of the vapour is absorbed by the material, transmitted through it by osmosis, then evaporated back into the air on the other side.

With (2), the interesting thing with wood is that it will absorb moisture, but then it's structure is specifically 'designed' to transmit moisture along the grain, rather than across it. With 'normal' timber, this means that it will tend to transmit the moisture up to the exposed end-grain (and this is one reason why treating just the ends of timber can have a disproportionately beneficial effect against decay).

The OSB, it does the same, but since it's made up of flakes of wood aligned parallel to the surface, the tendency is to transmit any moisture along the face of each flake (and back into the room), rather than through the thickness of the sheet.

Interesting stuff, is wood!

[Edited on 28/2/16 by Sam_68]

jacko - 28/2/16 at 07:08 PM

http://www.garagejournal.com/forum/

I have been reading this forum and links about people building new wood garages in cold and snowy country's
They all use obs boarding
have a look wow to some of the garages
jacko

Sam_68 - 28/2/16 at 07:21 PM

quote:
Originally posted by jacko
I have been reading this forum and links about people building new wood garages in cold and snowy country's


Another anorak fact about wood:

A lot of people think that wood decays if it is damp, but that if it isn't damp, it still decays, only much more slowly.

This isn't in fact the case: if you keep the moisture content of the wood below 20% by weight (normal 'dry' timber is between 8 and 12%), it will last pretty much indefinitely.

One of the examples I like to give for this is the furniture in the Egyptian pyramids, which is thousands of years old. The other (relevant to what Jacko has just said) is that there are timber churches in Scandinavian countries that are well over 1000 years old, and going strong.

When the air gets that cold, it simply can't hold enough moisture to cause problems.