Get the order of work wrong on the outside of a house, and the problem stays hidden for years. Then a damp patch shows up on a bedroom wall, and nobody can say where the water came from. By that point, the fix often means taking things apart.
The good news is that the right order is not a secret. It follows one simple idea, which is to keep water out at every stage. In these home construction tips, you will learn what goes first, what goes next, and why. You will also see how the order changes between brick, timber clad, and render finishes. There is a worked example, a pre-cladding checklist, and the mistakes that cost the most to fix. Whether you are building new or replacing old parts, this will help you plan the schedule and ask your builder the right questions.
Think Like a Raindrop
Water runs downhill, finds gaps, and sits in corners. Good building order copies that path. You protect the top first, then work down.
One home improvement columnist gives the same advice, saying to start at the exterior and go from the roof down, thinking like a raindrop. If you must choose between windows and cladding, the same source suggests doing the windows first.
Why Order Matters So Much
Every joint on the outside of a house is a place water can get in. Sealant alone does not solve that. Sealant fails over time from sunlight and movement, so the layers behind it have to do the real work.
Each layer should overlap the one below it, like roof tiles. That way any water that gets past the first layer runs down and out, not into the frame. You can only build that overlap if you fit things in the right order.
The Build Order at a Glance
Here is the usual sequence for a weathertight shell. Your designer or building control officer may change details, so treat this as a guide.
| Stage | What Happens | Why It Comes Here |
|---|---|---|
| 1. Roof structure and underlay | Trusses, sarking, or felt battens | Gets the building out of the rain first |
| 2. Window and door openings ready | Openings formed and checked | Sizes must be accurate before frames arrive. |
| 3. Breather membrane on walls | Wraps the frame and sheathing | Creates the main water barrier |
| 4. Windows and doors fitted | Sill pans, frames, and tapes | Seals the biggest weak spots |
| 5. Pipes, vents, and cables through walls | Penetrations fitted and sealed | Must be done before cladding covers them |
| 6. Cladding or outer skin | Battens, boards, brick, or render | Protects the layers underneath |
| 7. Final roof covering and trims | Tiles, slates, flashings, fascias | Finishes the outer shell |
Step 1: Get the Roof On First
A roof comes first because everything below it needs shelter. A wet frame, wet insulation, and wet floors cause delays and dampness that can hang around for months.
Roof Structure and Felt
Trusses or rafters go up, then the underlay and battens. Once the roof is felted, rain mostly runs off the building. Many self-builders say their windows went in as soon as the roof was felted, and some even had windows in before the slates went on, according to self-builders on the BuildHub forum. It is common practice, but check with your designer.
Leaks Start Small
A tiny gap at a roof edge or flashing can cause rot in the frame. Our guide to the dangers a leaky roof can cause shows how fast damage spreads, so do not rush this step.
Step 2: Windows and Doors Before Cladding
Windows and doors sit between the roof and the cladding. They go in after the main roof structure and before the final wall finish.
One technical guide explains that windows and doors must be installed before the final cladding is applied because of how moisture is managed. That is the core rule of this whole article.
Order Windows Early
Windows take time to make. One supplier suggests the best time to order is during the roof stage or just after it, when the openings are ready and can be measured accurately. Do not order from the drawings alone.
Build the Opening Layer by Layer
The same technical guide describes a pan flashing fitted under the sill first, then the window, then tape lapped in a set order. The aim is that water reaching the sill is guided out and away from the framing. Your fitter should follow the windowmaker’s instructions.
Protect the Frames
Once windows are in, other trades will be working around them. Some builders cover them with plastic sheeting until the outer skin starts. It is a cheap way to avoid scratched glass and damaged seals.
Step 3: Deal With Everything That Passes Through the Wall
Pipes, vents, flues, cables, and extractor ducts all pass through the outside wall. They must go in before the cladding does.
A New Zealand building guidance note makes the point that anything penetrating the cladding should be installed before the cladding, so it can be sealed to the wall underlay.
This is where your electrician comes in. Sockets, outdoor lights, and meter boxes all need planning. Read about electricians and Part P registration and how to approach choosing an electrician. The factors that affect electrician costs will help you compare quotes. Our electrical safety tips are also worth a read before work begins.
Step 4: Fit the Cladding Last
Cladding is the part everyone sees, but it should be the last layer to go on the walls. It protects the membrane and the windows from sun and rain.
Leave Room Around Each Window
A site photo in one building science article showed a crew starting cladding before the windows were in, without leaving enough space for the windows. That is more work at best, the author says. Check there is room for flashings and trims.
Do Not Put the Windows in Too Early Either
The reverse mistake is just as bad. That article also describes a home where windows were fitted before the breather membrane. The writer says this will probably lead to moisture problems because the membrane cannot be lapped properly over the window flashings.
How the Order Changes by Wall Type
The basic rules stay the same, but the details shift.
- Timber frame with timber cladding: roof, membrane, windows, battens, then cladding
- Brick outer skin: the brick often goes up around fitted windows, so cavity trays and lintels must be right
- Render on blockwork: windows go in before the render, and beads and trims finish the edges
- Steel frame kit homes: follow the kit supplier’s sequence, since fixings and panels are designed to go in a set order. Our look at the merits of steel frame kit homes explains the pros and cons.
A Real-Life Example
Picture a couple building a three-bedroom timber-frame house. They have a tight schedule and a hired crew. Their builder offers to start the larch cladding in week six, before the windows arrive, to keep the cladding team busy.
The couple asks a simple question: where will the window flashings go? The builder realizes the cladding would sit too close to the openings. They hold the cladding for two weeks, fit the windows, and tape the sills first, then start the boards.
That delay cost them a couple of weeks. But it saved them from lifting finished boards later and from the risk of water getting behind the frame. It is a typical example of a short pause that avoids a long repair.
Checklist Before the Cladding Goes On
Use this list with your builder before the first board or brick is laid. It is based on common cladding check items, such as enough clearance between the window frame and the stud wall and head and side flashings fitted to the guide.
- The roof is weatherproof, with underlay or final covering in place
- The breather membrane is complete and lapped correctly
- Windows are level, plumb, and sealed
- Head and side flashings are fitted
- All pipes, vents, and cables are in and sealed
- Cavity trays and lintels are checked on brick walls
- Building control has seen what needs inspecting before it is covered
Mistakes to Avoid
- Starting cladding before the windows are in
- Fitting windows before the membrane is in place
- Cladding over pipes and cables that are not yet sealed
- Ordering windows from drawings, not measured openings
- Relying on sealant instead of proper flashings
- Leaving the roof half done during a wet spell
What Comes After the Shell
With the outside sealed, the inside can move forward. Insulation, wiring, and plastering are next. Poor airflow and damp can harm health later, so read about indoor air quality in the house. Planning to build in a greener way? See green homes and how they are gaining popularity. A deck is easiest to plan once the walls are finished, so look at adding a deck. If your project is a renovation and not a new build, check when you will need an electrical rewiring before you close up the walls.
Conclusion
The right order outside a house is simple to say and easy to get wrong. Roof first, then windows and doors, then anything that passes through the wall, and cladding last. Each layer overlaps the one below, so water runs out and not in.
Before your next build meeting, ask your builder to talk you through the sequence for your own walls. Then use the checklist above before any cladding goes on. A short chat now can save you a very long repair later.
FAQs
What is the correct order to install a roof, windows, and siding?
Roof first, then windows and doors, then cladding or siding last. This keeps the frame dry and lets each layer overlap the next.
Do windows go in before or after cladding?
Before. Windows and doors need flashing and tape under the cladding, so the water barrier stays continuous.
Can I install windows before the roof is finished?
Often yes, once the roof is felted and the structure is weatherproof. Follow your designer’s drawings and the window maker’s instructions.
Why should pipes and vents be fitted before cladding?
They pass through the wall and need a proper seal to the membrane. Once the cladding is on, that seal is hard to reach.
When should I order windows for a new build?
Order during the roof stage or just after, when openings are formed and can be measured. Allow plenty of lead time.