A brick built garden room is a small building rather than a structure in a garden, and everything follows from that. The foundations go deeper, the trades multiply, the programme lengthens and the finished thing reads as permanent to a neighbour, a valuer and a planning officer. In exchange you get thermal mass, security, a long life and something that looks like it belongs to the house.
The foundation is the real difference
Masonry is heavy and it is unforgiving of movement, so the foundation is a designed trench fill or strip footing taken down to suitable bearing rather than a slab on good ground. On clay with trees nearby that can be a great deal of concrete, and it is why two quotes for the same brick room at two houses can differ so much.
More trades, in sequence
Groundworker, bricklayer, carpenter, roofer, glazier, electrician and plasterer each have to wait for the one before. That is a longer programme, more weather exposure and more coordination than a panel building that arrives on a lorry, and it shows up in the price as much as the materials do.
Where the exemption stops
Small detached buildings can be exempt from building regulations approval on floor area, boundary distance and use conditions. A substantial masonry building can exceed the floor area condition, and its walls are not of the lightweight construction the exemption's distance rules were written around. Check the position for the actual design rather than assuming an outbuilding is automatically exempt.
Matching the house, or deliberately not
A brick that nearly matches the house reads as a mistake for the life of the building, and one that clearly contrasts reads as a decision. Good bricklayers will say which is achievable, and a render finish or a deliberately different brick is often the better looking answer as well as the cheaper one.
Questions people ask about brick built garden room
Is a brick garden room worth the extra?
If you want permanence, security, sound insulation and a building that looks like part of the property, yes. If you want the maximum internal space for the budget in the shortest time, a well specified panel building beats it on every one of those measures.
Does it need planning permission?
The same outbuilding tests apply on height, boundary distance and coverage, and masonry does not change them. What it changes is the visual impact, which matters in a conservation area or where an Article 4 direction has removed permitted development.
How much internal space do I lose?
A cavity masonry wall is considerably thicker than a well specified panel wall for a similar thermal performance, so a brick room gives less internal floor from the same external footprint. On a small building that difference is noticeable.