Garden room, help with height and overhang

[Wils81]

I'm in the process of designing a garden room and would really appreciate some help.

I plan to build it with 4 timber rafts bolted together and sitting on concrete blocks. . Garden is long and narrow, so planning 5.5m front to back and 4.5m wide. So max span of each individual raft would be in the region of 2.75m. Not sure if building 6 rafts would be better? I'm really struggling to get it under 2.5m with a flat cold roof with all the joist sizes. I could run the roof joists on the 4.5m span but then with adding firrings for the fall, it wouldnt make much difference to having bigger joists running front to back. Am I over calculating or should I just apply for planning and 3m height?

Also, when calculating the 1m space from the boundary, does roof overhang count? Was thinking of a small 30cm overhang on the sides

Tia

 

[noseall]

I'm in the process of designing a garden room and would really appreciate some help.

I plan to build it with 4 timber rafts bolted together and sitting on concrete blocks. . Garden is long and narrow, so planning 5.5m front to back and 4.5m wide. So max span of each individual raft would be in the region of 2.75m. Not sure if building 6 rafts would be better? I'm really struggling to get it under 2.5m with a flat cold roof with all the joist sizes. I could run the roof joists on the 4.5m span but then with adding firrings for the fall, it wouldnt make much difference to having bigger joists running front to back. Am I over calculating or should I just apply for planning and 3m height?

Also, when calculating the 1m space from the boundary, does roof overhang count? Was thinking of a small 30cm overhang on the sides

Tia

This shed I built a year or so ago is bang on 2.5m at the highest point...

20221203_133018.jpg

• noseall
• 4 Dec 2023

shed.jpg

• noseall
• 4 Dec 2022

 

[Wils81]

Apologies, meant to put in the measurements. So I've allowed from ground up

50mm gap underneath floating rafts
125mm floor joists
18mm osb
12mm flooring
13mm plasterboard ceiling
195 roof joist (if going 4.5m span)
100mm firring for fall
18mm osb

So 531mm, less the 2.5m and my head height is far too low internally

 

[big-all]

general comments
if less than 2m from boundery your roof overhang is irrelevant as long as its on your land and any water it sheds is on your land
is the site dead level if not highest point it covers is the datum point

between 15 and 30 square m it will probably need to comply with building regs

dont assume you will get planning permission as its not gteed a crowded site may be greater than 50% as built ect

 

[Wils81]

Trying to get walls as close to 1m from boundary as possible, so roof overhang if at 300mm would be 700mm from boundary but if overhang is irrelevant I'll be fine

My understanding is anything under 30 sq m doesn't have to comply with building regs, if 1m from boundary.

Garden is 40m long, so I've got no issues with 50% of site

 

[big-all]

dont forget its the floor area you count,for sqm not the outside

the 15-30 thing say just says you probably wont or words to that effect
i have always understood it was wall to fence rather than structure to fence but stand to be corrected

 

[Larry1990]

I got planning permission for a 3m high garden room a metre from my boundary with minimal hassle. I'd say it was well worth a couple of hundred notes to have the extra room so you can have the head room you want and not have to worry where you can save mms here and there. It also allowed for a warm roof so very happy with that.

Cheers

Larry

 

[big-all]

another thought
if its your fence /Boundary, it's the actual Boundary and this can be the far face off the posts if they are facing the boundery now i realize we are only talking a possible 50-100mm but worth a mention