Build Your Own Summer House

If you’re following us on instagram or facebook, you’ll see that whilst we’re waiting for planning permission to crack on with our extension, we’ve been getting the outside areas ready to go.

Initially, this involved garden clearance and some landscaping, albeit more than we expected due to many rotten trees and dangerously overhanging branches. Check back to our blog here if you’d like to know more:

However, ripping out more than we’d anticipated from the garden did end up paving the way for us to put our summer house down the end of the garden. Have you ever thought to build your own summer house? Well, it was a first for us. Ordinarily we would order a summer house that is supplied and built by specialists. On this occasion though, given our exacting requirements, we decided on a DIY version. This was because we wanted it bespoke to our size requirements and as our intended use is as a gym, we wanted a solid floor base to withhold weights being dropped and pounding from gym equipment such as treadmills.

But first things first…

If you’re going to build your own summer house, do you require planning permission?

Well, ultimately this all depends on the size and purpose of your summer house. On investigation on the planning portal, outbuildings are allowed under permitted development, not requiring a planning application, provided these following conditions are met:

  • Outbuildings must not exceed 50% of the total area of the land around the original house
  • Any new building must not be used for living accommodation
  • It can only be single storey with a max eaves height of 2.5m and max overall height of 4m with a dual pitched roof, or 3m in any other case (e.g. 3m max for a flat roof)
  • Must be 2m in from the property boundaries on all sides (otherwise height restriction reduces)
  • Balconies/verandas aren’t allowed

There’s a few other conditions to consider if you want to build your own summer house, but above are the key ones for a residential house.

Given we’re lucky to have a huge garden and don’t plan to use the summer house to live in, in theory we can therefore build away size-wise to our hearts content. And this is part of the reason why we chose to build it ourselves this time so we could build it to our exact size requirements, optimising the space whilst staying 2m in from the boundaries, and respecting the 3m height limit.

With a plan in place…let the build begin

So what are the steps to take if you want to build your own summer house?

The below steps are for building a timber framed summer house or outbuilding, but bear in mind ours will be all done to a high spec as we wanted a solid floor fit for a gym, a fully insulated space for warmth and electrics for gym equipment. Although it won’t be used for living accommodation or have plumbing, the spec is pretty similar to what you would do when building a timber-framed house and would be building reg compliant, from the damp-proofing to the insulation! I’ve also outlined below how many days it took to build, bare in mind these are ‘working’ days, you’d need to factor in time for setting/drying too.

Day 1 – clear and level the area

We hired a machine driver / digger in for the day to dig out everything on the ground, rip out tree roots, and then scrape / level the ground ready for the base.

Day 2 – build your frame & damp-proof

The frame base surround was built into the ground with 8 x 2 treated timber, and inside the frame the ground was then filled with 100mm Type 1, levelled and compacted with a whacker. A layer of damp-proof membrane was then laid across the whole floor base with steel mesh put on top raised by castles so the mesh doesn’t touch the membrane and the concrete will be able to flow underneath the steel mesh when poured.

Day 3 – create the concrete base of the summer house

The floors then had 100mm of outside liquid screed pumped in and levelled, and this was then left to set to create a proper solid base with damp-proofing underneath.

Day 4 – engineer your summer house out the ground

With a solid base in, what is next when you want to build your own summer house? Next stage is to engineer it out of the ground, so a brick layer then came in to engineer it up to damp course level (with engineering bricks) ready for the timber frame to be built on top. A layer of damp course is laid on top of the bricks.

Days 5-6 – build the timber frame of your summer house

The frame of the summer house was then built on top of the engineered brick and damp course with 6 x 2 timbers all around, allowing gaps for any windows and doors. The walls are then ply-lined with WBP (water-based ply).

Days 7-8 – get your summer house in the dry

With the timber frame walls up, you can focus on getting it in the dry and likewise build your own summer house roof with the same 6 x 2 timber. Firrings are then laid on top of the new roof joists which create a slope when you’re putting in a flat roof so that rain water can fall off. 18mm OSB boards (oriented strand boards) are then placed on top of the firrings followed by 3 layers of roofing felt for the finished roof. OSB is increasingly used over plywood as it’s stronger.

Arris rails were then attached along the front, back and sides of the building to also ensure rain fall off, and soffits / fascia boards put up around all the edges where the roof meets the external walls to support airflow and the guttering.

WBP is then used to form the external walls, attached to the frame of the 6 x 2 timbers. A breathable membrane is then battened in to place on top of the WBP on all sides of the house so it’s now ready for whatever cladding we decide to add for the finishing touch externally. We’re holding fire on the cladding for the time being, as we want to match the cladding in with whatever we do for cladding on our actual house and we’ve not decided on this yet.

Day 9 – door & windows

The last step to then get your summer house in the dry is to install the doors and windows – now the building is secure too so we can start to store things in it.

Days 10-11 – internal flooring of your summer house

If you’re going to build your own summer house more as an outdoor shed you can of course just build it out of timber on top of a level patio surface without thought to damp-proofing, insulation and the likes. This will certainly be a lot quicker and much less costly if you’re just using it for storage and it doesn’t matter if damp gets in. However, if you want to be able to use it as an office or functional room with warmth, damp-protection and be able to decorate it, these steps for sure will future-proof it for the long term.

With the summer house now in the dry, we can finish the space internally. A layer of damp proof membrane is laid across the entire floor and lapped up the walls. 100mm insulation is then laid across the floor, a second layer of membrane laid on that, and finally a 75mm top layer of sand & cement screed is pumped in on top. It has an accelerator mixed within it so that it cures (sets) quickly. Otherwise it would take c. 1 day/mm to dry, depending on weather conditions, which could take several weeks! Not happening.

Days 12-13 – internal walls, ceilings & first fix electrics for your summer house

We then insulated the walls and ceilings internally with 100mm RWA 45 – we didn’t use kingspan primarily as it’s just a thermal insulation where as RWA is fireproof and also offers sound proofing insulation as well as thermal.

If you’re going to build your own summer house you must also consider what electrics/plumbing may be required. Just bear in mind if you’re thinking of putting any plumbing in, this may then be considered “habitable” and require some form of planning permission, so consider this carefully versus your intended use.

With internal walls now built and insulated, our electrician was then on site to do first fix electrics allowing for lighting requirements and sockets.

There will be 100m of armoured cabling going in and 100m of data cabling so we can have full functioning wi-fi/internet in the summer house. As we’re planning to use it primarily as a gym, modern gym equipment often requires internet connections nowadays to join virtual classes, and we’re also going to have a “chill” area in the corner with a TV so the kids can hang with their friends and watch likes of Netflix or Amazon Prime. This will all link back to the fuse board in the house.

We then boarded the ceiling with 12.5mm plasterboard, and boarded the walls with MDF. We also used 3 x 2 timbers to build a stud wall for a cupboard in the corner of the room which was likewise then boarded that with MDF too.We could have plasterboarded the walls but we want to be able to put TVs, mirrors, pictures and the likes up on the walls and MDF will be stronger to accommodate this. The electrics were pulled through and then the walls/ceilings were all skimmed ready for painting.

Electrics were also pulled through externally in readiness for outdoor lighting too and we’re just waiting for a final visit from the electrician to fit these too

Days 14-15 – Final touches and decoration

Last stage now on our “build your own summer house” step-by-step guide. The smooth, skimmed walls are now crying out for a touch of paint so the decorator has been in to give them some colour. We used Dulux trade paint, and had this colour matched to the Farrow & Ball Strong White and Off Black.

And last of all the cupboard in the corner has been shelved and the electrician has been out for second fix to install the lights and socket plates.

We also made a last minute decision to add skirting and architrave to finish the look, so these and now just waiting to be painted too and the electric heaters to be added.

So in around 3 working weeks you can build your own timber summer house or outbuilding from scratch, with full damp-proofing, insulation and electrics. If my husband was quoting this for a customer, he’d probably say to allow 3-4 weeks, subject to weather of course too. Although ours isn’t going to be used for living accommodation, if you were looking to build a habitable space requiring planning permission and compliance to building regs, you’d also be able to follow the same steps as we’ve not cut any corners, just adding in the plumbing requirements in too.

But from our side we’re all finished, bar the external cladding which will follow later, and ready to turn it in to a gym now… watch this space.