Insulating a garage - some advice needed on the floor and approach

AdamUK · Post by **AdamUK** » Mon Jan 13, 2020 10:31 pm

Hello

I've got a standalone garage outside my house. It's single brick (over 110mm think as it's 2 courses) and I want to insulate it. The reason I want to do this is for storage purposes and I've got electric running to it so I can keep an oil radiator or something in there to keep the temperature controlled >15c.

I've decided to build a false ceiling inside it, so that there isn't' any load on the roof structure and I've already vented the garage at both ends to ensure the insulation in the roof space doesn't end up all damp. The ceiling will be a fairly standard approach with a good, thick wool insulation at the top.

I've order Kingspan Kooltherm K18 50mm/12.5mm Insulated Plasterboard and I'm going to mechanically fix it using treated roof battens that have a DPC behind them as per the instructions.

The query I have is with the floor. There is a solid concrete floor at the moment and I know that there are a couple of options here using a floating or screed based approach. I realise that I will need to put down a DPM and then something like kingspan or Celotex on the floor - perhaps 20/25mm super-strength stuff with either a floating floor using 18mm chipboard / or screed.

I cannot afford for the floor to be raised to much because I intend to install a highly insulated garage door to keep it "functioning as a garage". I hope that I'm within my right to do the work I want given that this garage is completely standalone and I want to store stuff in it! I expect building control will probably say otherwise.

With the DPM for the floorI read that someone's advice was to take this up the wall beyond the DPC in the brick by 20-30cm. Would I be right in saying that I do this first before installing the walls with the battens with the DPC? or do I do that once I've battened out the walls and fixed the Kingspan Koolterm to it?

Any help would be most appreciated

:dunno:

Adam

Rorschach · Post by **Rorschach** » Tue Jan 14, 2020 7:35 am

What are you planning to store in it that requires these efforts?

AdamUK · Post by **AdamUK** » Tue Jan 14, 2020 8:05 pm

Many things from soft furnishings etc.

I am also considering putting a treadmill out there too which will probably gather dust (but I may use from time to time) but who knows. I want to make sure that anything I do put out there doesn't just rot away over time. Everything in garages just ends up with a sort of dampness no matter how much plastic you wrap it in...

Any advice?

London mike 61 · Post by **London mike 61** » Tue Jan 14, 2020 8:59 pm

Check out this link , its one way of insulating the floor.

https://youtu.be/OrYgHJee3XI

Mike

Rorschach · Post by **Rorschach** » Tue Jan 14, 2020 9:28 pm

Insulating won't stop dampness.

If the items are not temperature sensitive then just seal up the gaps letting cold and wet in and run a dehumidifier in there, that will keep it dry.

AdamUK · Post by **AdamUK** » Tue Jan 14, 2020 10:05 pm

Rorschach wrote: ↑Tue Jan 14, 2020 9:28 pm Insulating won't stop dampness.

If the items are not temperature sensitive then just seal up the gaps letting cold and wet in and run a dehumidifier in there, that will keep it dry.

Yes, I know that we will need to keep the temperature at a certain level which can be achieved with a radiator or something of that kind as insulation simply slows heat loss.

It's a fair shout and i've run dehumidifiers before but its a vast space so it's going to be a losing battle. As I've now committed to the project so I'll insulate it. If I want to use it as a workshop, or even for gym equipment I've got future options.

I think I will lay a DPM down on the floor and up the walls and then just batton it out and insulate. That will then allow for a future floor to go down should it be required whilst things being able to be placed on the floor without the worry of drawing mostuire up from a massive concrete slab.

Rorschach · Post by **Rorschach** » Wed Jan 15, 2020 7:20 am

No I said the heat isn't important unless you are storing things that are temperature sensitive.

If it's a vast space then keeping it warm is a losing battle, keeping it dry isn't. It's a lot easier to keep a space dry than warm because moisture doesn't conduct through surfaces like heat does.

Anyway it seems you already know what you wanted to do before asking for help so I'll let you carry on.

AdamUK · Post by **AdamUK** » Wed Jan 15, 2020 8:25 am

Rorschach wrote: ↑Wed Jan 15, 2020 7:20 am No I said the heat isn't important unless you are storing things that are temperature sensitive.

If it's a vast space then keeping it warm is a losing battle, keeping it dry isn't. It's a lot easier to keep a space dry than warm because moisture doesn't conduct through surfaces like heat does.

Anyway it seems you already know what you wanted to do before asking for help so I'll let you carry on.

And I said initially I wanted the garage to be warm >15c. Perhaps I want to store supercars? Or my electric car? Or use the space for a gym or workshop?

I take your point insulation doesn’t prevent damp but damp proofing does - however changes in temperature creates moisture in the air and dehumidifiers deal with that.

Your right to question the need for belt and braces - it’s not necessary to use 50mm Kingspan so I’ve decided not to.

I thank you for replying and your points are valid. So much so that I’ve decided not to use the Kingspan to the depth I was quoting - it’s not a dwelling and therefore U values don’t really matter as much