Garage Renovation

[harrytheh]

Dear All,

I am new to this forum and have tried to find information already created with regards to garage renovation, but I still have some questions!

The most similar post that I found with regards to the general idea is this:

//www.diynot.com/forums/viewtopic.php?t=227249

In my garden there is an existing garden shed made of concrete blocks and beams with a corrugated steel roof - it is ancient and will soon be coming down! It is of a similar size to the project shown in the link above.

In its place we would like to create a new garage which instead of storing tools, will have electrics to store a separate fridge (add power outlets), spare food (we buy a lot of goods in bulk) and other general household stuff, hopefully alongside and sofa and tv (if i'm lucky).

I am trying to get a general idea of the construction style this building will entail before I ask an architect friend to help me with some plans (for planning perm.) I would like the building to have a decent level of thermal insulation to create a comfortable space (for storing the food and even for watching tv/having a few people over). I would like double glazing for two windows and entrance. The roof can be a pitched rafter with insulation infill.

My uncertainty lies in whether to go the whole hog with double-leaf cavity insulated walls (expensive, reduces the inner dimensions), or to try and find a balance in some kind of half measure?

Can anyone recommend their idea of the best wall construction method?

Many thanks

H


Edit:

I made this quick cad model to show the general scheme.

View media item 31955
PS. Can anyone give me a name for this project that better suits the building.. garage isnt quite right (imo) and outhouse sounds like a toilet..

PPS.
I am also concerned at the moment as to how long/narrow the building might be (something I still need to think about but hoping the wall construction can take up as little internal space as possible.

 

[harrytheh]

Can anyone here offer any help?

 

[ajrobb]

What you've described probably counts as habitable 'garden room' and needs to comply with building regs, including insulation:

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1B_2010.pdf

As long as your final design heat loss is no worse than a 'prescriptive' design you can compromise on one bit if you improve another. For instance, you might be prescribed a maximum 25% of the floor area as doors and windows with a U-value of 1.8 (that is for extensions, but might be the same), if you go for smaller or better windows, you might be able to increase the U-value of the long walls.

Let's say the garage was 8'x16' internally, call it 12m². You could have 3m² of doors and windows (including frames) with a U-value of 1.8. Assuming a ceiling height of 2.4m, you have 35m² of wall (including doors and windows).

So the total permitted heat loss from the building would be 0.28 * 32 (walls less doors and windows) + 1.8 * 3 (doors and windows) + 0.18 * 12 (roof with insulated rafters) + 0.22 * 12 (floor)

19.16 W/K

 

[wavetrain]

Can anyone here offer any help?

I would not worry too much about ajrobbs proposal, you are not going to heat the place so part L does not apply. Who has heard of conserving heating energy in a building without heating?


Why not put in a planning application for an outbuilding with walls 100 - 110mm thick (dense concrete block or brick - do not use 100mm airated blocks as your building will be all floppy) with piers now and then along the walls. It will not need building regs as it is less than 30m2 and built from non combustible materials outside.

When finished if you choose to fix 4.5" studs at 400mm centres and insulate with mineral wool, staple a vapour barrier and finish with 12mm chipboard so be it.

If you later decide to put a sofa in there, no problem as long as you are not going to live in there, but if you do live in there you have broken planning law by living in a non habitable building and the Council will hound you down.

I would advise however that you should not use uPVC for windows and doors, but rather hardwood to give a more rustic feel to the place and for soft landscaping so it blends into the garden.

 

[harrytheh]

Thank you very much for your time in responding.

Both of you have given me a lot to think about with regards to the quality of the space inside that I am trying to achieve. This will be easier defined once I fully assess the working dimensions of my plot.

I am fully clued in on the "eco" building side of things, and could easily specify a passivehaus reg garden/home/out/house, weirdly its the more basic approach I know less about!

I will no doubt return in the coming weeks with more questions.

 

[ajrobb]

If the existing 'ancient' garage pre-dates 1948 or is on original plans after that date, it will be part of the ground area used to calculate permitted development. You should be alright to replace an existing outbuilding with another outbuilding without planning permission if its not a listed building, a conservation area, park etc.

Have a look at http://www.planningportal.gov.uk/permission/responsibilities/planningpermission/permitted as you might be able to extend as well.

Maybe I'm too soft, I associate sitting on a sofa watching TV with heating.

Have a look at:
http://www.insulateonline.com/index1.htm?walls5.htm~main

85mm timber frame construction with brick cladding => U-vale of 0.27. Change brick cladding to render on mesh and you could be close to 100mm total. Having 10% timber and 90% PIR gives an average K-value of 0.033 rather than 0.024 for a full layer of PIR.

Take 60mm at 0.033 => R-value 1.82 (timber frame)
add 40mm at 0.024 => R-value 1.67 (full layer PIR)
add surface values => R-value 0.17
total R-value 3.66 => U-value 0.27 (less than required 0.28 )

You get a tiny bit more insulation from plasterboard and render.

 

[harrytheh]

I would be inclined to agree.. we would like it to be a comfortable space at least on one side so a good level of insulation would be preferable - if only to negate the cost of having a small electric heater in the room (such a small volume wouldn't take much heating anyway, but insulation and a vario membrane wouldn't hurt to insure it remains inside).

ajrobb your link hits the nail on the head I think!

The house is a 1930s end of terrace build, the garage I have no idea how old but its got an asbestos roof - we are fully aware of those implications and will ofc need to get it professionally removed.

I believe we will be extending it somewhat (why not, whilst we're at it!). My father who lives in the family home where this will be built has already ascertained that we need planning permission. The application is on hold until we can provide plans.

 

[wavetrain]

Ihaving a small electric heater in the room

You are not going to have anyone live in it are you now?

 

[harrytheh]

Ihaving a small electric heater in the room

You are not going to have anyone live in it are you now?

Definitely not - as I said, mainly for food storage, our second fridge, few odd bits and if there's any remaining space, some kind of sofa and a tv

 

[wavetrain]

I can visualise it all now, feet up on the footstool aka poof, blueray DVD playing latest blockbuster, and all the food and drink your heart desire's!

Watch that waistline

 

[ajrobb]

And next winter, when the boiler condensate freezes, you'll have a warm refuge. A few candles and you'll get enough heat.

Using 1 candle as roughly 80 W (similar to one person) and 20 W/K for the new room, each candle or person would maintain roughly 4°C extra warmth. Put a plasma TV in there and you'll be toasty.

 

[wavetrain]

A few candles and you'll get enough heat.

You will need ventilation to remove the products of combustion from the those candles. So vent bricks top and bottom of wall please.

 

[harrytheh]

And next winter, when the boiler condensate freezes, you'll have a warm refuge. A few candles and you'll get enough heat.

Using 1 candle as roughly 80 W (similar to one person) and 20 W/K for the new room, each candle or person would maintain roughly 4°C extra warmth. Put a plasma TV in there and you'll be toasty.

I actually know first hand how little it takes to heat a super-tight insulated house - obviously not striving for that in this situation, but your comment about the boiler condensate freezing has me concerned :S

Was that a joke or are you implying leaving a portable electric heater in the room would leave it susceptible to freezing over in winter? In anycase it would be an easy task to move it to the house and only bringing it back when we wanted to use the room.

Wavetrain - for my own education can you please provide a diagram or a link describing the actual implementation of vent bricks at the top and bottom of a wall - i.e. a construction drawing of them in place.

From my own knowledge I know to limit cold bridges as much as possible, so a direct ventilation would go against this.

Then again products like this claim to help:

http://www.airtechenvironmental.co.uk/pages/vapourvent.html

But I dont know how good they are for "products of combustion - CO2, CO"

PS I should clarify I don't actually intend to burn anything inside this room, but incase there ever was a candle

 

[ajrobb]

Approved Document F: Means of ventilation
http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADF_2010.pdf

Oh joy!

Table 5.1b

0.3 l/s/m² and 4 l/s/person

 

[wavetrain]

Was that a joke or are you implying leaving a portable electric heater in the room would leave it susceptible to freezing over in winter?

I'm not sure if you are being serious H, but ajrobb's joke was about the condensate freezing on a hyperthetical condensing boiler heating your house. The electric heater will be in your new cabin at the bottom of your garden is it not?