The other day we wrote an article for publication on The Garden Room Guide looking at a mono pitched garden room in a London garden. In most cases when writing about such a building we will say that it has been designed to be 2.5 meters high so that it can comply with the Permitted Development rules. Permitted Development rules say that a garden room 2.5 meters high or less can be sited within 2 meters of the boundaries of the garden.
This building was different in that the designer and their client had made the decision to apply for Planning Permission so that they could build a garden room 2.7 meters high. They decided to do this so as not to compromise on their preferred build-up.
The supplier builds off a house quality, traditional timber framing system. They decided to comply with the 2.5-meter rule , they would have to compromise on the timber thickness used in the build-up of the floor and roof – this is admirable.
This is something your should consider when designing your garden room
This is something you should consider yourself when designing your garden room. The 2.5 meter Permitted Development rule is appealing, but from a design point of view, you might be better to take your time and make a Planning Permission application and build the height of garden room your design dictates.
Things to weigh up
When measuring the height of a garden room, the measurement is taken from the highest piece of ground immediately adjacent to the building to its highest point.
When you have a fixed height of 2.5 meters to work with you need to identify your fixed dimensions first. This will often start with the doors, which with a frame will be 2090mm. You should allow 2100mm (2.1m) for fixing. This leaves you with 400mm to play with.
You will need a lintel over the door to support the roof – say you allow 100mm for this, that will leave you with 300mm to play with. Some suppliers who use light-weight frames for their garden rooms will omit this lintel to save some height. They either just use a 50mm timber header or rest the roof structure on the door frame – we don’t advise either method.
The remaining 300mm is divided between the floor and roof structures. Both of these sections need to have substantial timbers to prevent sagging and also to house a suitable amount of insulation.
Typical 2.5-meter garden room build-ups
In these two drawings, we have modeled up two different 2.5-meter high garden room build-ups. The first one has a warm roof build-up, the other makes use of a preformed insulated roofing sheet – both options are commonly used in garden room design:
A typical 2.7-meter high garden room build-up
We started this post by explaining how a garden room designer didn’t want to compromise on their structure to build a 2.5-meter garden room. Instead, they decided to apply for Planning Permission so they could build to 2.7 meters.
We have drawn up a typical 2.7-meter high garden room build-up with a warm roof. You can quickly see that the extra height you have allows you to increase the size of the floor timbers and beef up the lintel over the doors. The added bonus is that the garden room will also have a greater floor to ceiling height.
We hope these drawings give you food for thought. You need to decide if a 2.5 meter high garden room is right for you.