Planning & preparation
- This guide outlines the method for installing a single level deck with a timber frame and horizontal deck board positioning. Bear in mind that other decking designs will require different techniques and joist spacing.
- Start by deciding the location of your deck, bearing in mind factors such as sunlight and privacy. Try to avoid heavily shaded areas as they will require more maintenance, and avoid damp areas completely.
- Carefully plan your deck before starting, as this will limit cutting and wastage, and will help you to be accurate when ordering the materials you need.
- When designing the deck, remember to factor in gaps of 5-8mm between deck boards into your plans.
- If you are going to build your decking next to a house, make sure it’s 150mm below the damp proof course and that you don’t cover any air bricks.
- Plan the deck to ensure the fall of the frame is 1:100 and running away from the house, this will aid water run off and will help to stop the deck from becoming slippery. Bear in mind this fall when checking the levels throughout the build.
- We would advise that you plan your deck to fit only whole deck boards, to avoid having to cut a deck board lengthways to fill a gap.
Do it right
- Always use structural treated timber and screws designed specifically for the job. This will ensure that the deck is built to last.
- Treat all cut surfaces and drill holes with two coats of preservative.
- When sawing, use the 90-degree guide marker on your saw, or a set square, to help you make accurate cuts.
- When drilling, mark out all pilot holes to ensure your fixings are as accurate as possible.
- Sand cut ends of timber to remove splinters.
- If you need to cut a board lengthways, do it with either a handsaw or circular saw, and place it at the area of least through traffic. Then, lay your deck boards from the opposite end.
- It is possible to build a deck on your own, but it is much easier with a spare pair of hands, so ask a friend if they can help out.
- Firmly secure the timber and take care when sawing or drilling.
- When drilling, it’s best to wear safety goggles.
- Wear protective gloves when handling the deck boards or applying wood preserver.
- Always follow manufacturer’s instructions for drying and safety when using wood preserver.
- Wear safety goggles and a dust mask when using a jigsaw.
- Wear a dust mask when sanding any cut ends of wood.
- Offcuts of treated timber should be disposed of safely and shouldn’t be burnt – a recycling centre should be able to advise on the best method.
- Bear in mind that joists can be heavy, so take care or ask for assistance when moving them.
- Once the decking is complete, apply a decking stain to further protect the timber. These come in a variety of colours so be sure to look at the range.
- If you choose a shady spot, it’s best to clean and treat the wood annually to help preserve the timber.
- To keep the deck clean, remove any dirt or leaves with regular brushing.
Preparing the area
An existing patio or concrete base can be used as a solid foundation for your deck. Start by measuring and marking out your decking area.
If laying the deck over lawn, mark out the area then dig out to a depth of 50mm. Cover the ground with landscaping fabric and add gravel. For soft ground, place paving stones on top of the gravel; this will support the joists and preserve the timber.
Adding A Wall Plate
If you are building a fixed deck that joins onto a house then you will need to attach a wall plate. If you are building a free-standing deck then skip to the ‘Assembling the frame’ section.
Start by marking a vertical line that ultimately the end of the wall plate will be placed against. This will mark the corner of the decking.
If planning around a step or a sill check the design fits by taking an offcut of deck board, holding it up to the lowest part of the sill and marking a small line beneath it.
From that line, drop the board down by 10mm to allow for expansion and draw a level line using a spirit level. This line will be the guideline for attaching the wall plate to the wall so extend this line across the full width of the decking if possible.
Then, cut the joist to length. If you need to avoid any obstacles, such as a pipe, then measure and cut the joist accordingly.
Measure 100mm in from one end and mark the wood and, using a set square to ensure a straight line, draw a vertical line down from your mark.
Measure 50mm down from the top of the line and 50mm up from the bottom and mark the wood; this is where the pilot holes will be drilled. Repeat this process at 600mm intervals down the length of the wall plate.
Upon reaching the far end of the wood, measure and mark out another 100mm section.
Drill the pilot holes using a 6mm drill bit.
Put the wall plate into position in line with your guideline and use packers to support the timber if needs be. Check the wall plate is level.
Before securing the wall plate to the house, double check the deck board fits beneath the sill.
Drill guide holes into the wall using a 7mm masonry drill bit. It’s best to ask someone to hold the timber in place for you whilst you drill the holes.
Move the wall plate away and complete the holes by drilling directly into the wall.
Take the wall plugs and insert them into the drilled holes; you can use a hammer to push them into place. Then, move the wall plate back into position, making sure it’s still in line with the original corner mark on the wall.
Insert 6mm x 100mm screws through the holes in the wall plate and hang galvanised or plastic washers on the end. Use enough washers to ensure a 10mm gap between the wall and the wall plate.
Hand tighten the screws into the wall plugs before using a drill and driver bit to secure them. If there is an obstacle repeat this process to attach the second plate to the wall.
Assembling the frame
If your decking is going to be longer than the decking joists, you will need to join two sections together. If you don’t need to join your joists then move them into position and skip to step 6.
To join your joists, start by measuring and cutting the section you need to reach the required length.
Measure and cut a 600mm section and mark at 300mm to show where the centre point is. Secure the three sections in your workbench or saw horse, ensuring that the 300mm mark lines up with the join in the joists.
Measure 75mm from each side of the join and mark the wood. Then measure 150mm from each side of the join and again, mark the wood. From each of the four marks, use a set square to draw a straight vertical line.
Mark two evenly spaced pilot holes onto each of the lines you have drawn. Drill pilot holes using an 6mm wood drill bit. Secure with 100mm screws. Countersink the screws if you are adding fascia boards. Then, move your joists into position.
The frame should be at the required level before fixing, so place risers, paving slabs or treated offcuts of timber at 500mm intervals, then check with a spirit level. Also check that the corners are square using a set square.
To join the frame, mark and drill pilot holes before fixing two external grade 150mm timber drive screws into each corner. If you are adding a fascia then you will need to countersink the screws.
If some corners of the decking are hard to access, secure the joists by drilling skewed pilot holes at a 45-degree angle into the wood and fix with 100mm external grade screws. Once the frame is secure, double check that it is at the required level.
Adding internal joists
To work out how many internal joists are needed, measure 400mm from the centre of the external joists and draw a mark. Measure from this mark and repeat at 400mm intervals across the rest of the joist, making sure you never exceed the recommended spacing.
Once you know how many internal joists you need, you can measure and cut accordingly.
If you need to extend your internal joists, follow the same method as you did to join the external joists but with the addition of an extra 600mm section on the opposite side, to sandwich the joist in place. Offset the bolts slightly so they don’t come into contact.
Secure the joist in your workbench and attach a joist hanger to each end using 30mm exterior screws.
To secure the joist to the frame, place it into position with the centre of the joist lining up with the 400mm spacer mark. The joist needs to be flush with the exterior frame, so use an extra pair of hands or packers to keep it in place.
Use a set square to extend your 400mm guide marker down onto the external face. From this line, measure up 40mm from the bottom and down 40mm from the top, and mark two pilot hole guides.
Drill the pilot holes using a 6mm wood drill bit. Then, drill countersink holes and secure with 100mm timber drive screws. Repeat this for the rest of the joists, but always make sure the top of the joist is flush with the frame before securing.
If you have to secure the joist onto an unexposed side of the frame, drill two skewed pilot holes on each side before securing with screws.
Once the joists are in place, add the final 30mm screws to each joist hanger. Repeat this until all of the joists are secure.
Measure out and prepare enough noggings so that the distance between them will never be greater than 1200mm. To avoid having to skew screws, it’s best to stagger the noggings; bear this in mind when planning where they will be positioned.
To attach them, put the nogging into position and add packers if necessary.
Draw a line down the centre of the nogging’s position on both of the joists it will join to. Then, measure and mark pilot hole guides 40mm from the bottom and 40mm from the top on each side.
Drill pilot holes before securing the nogging with 100mm external timber drive screws. Once all the noggings are in place, do any final levelling and check that all joists are supported at 500mm intervals.
If your decking has an obstacle, such as a drain, add extra noggings around it for additional support.
Laying the deck boards
When laying deck boards, it’s best to pre-drill all holes with a 2mm bit to prevent damage or splitting. You can also countersink the holes to get a smoother finish.
If you are attaching a fascia board, allow for an overhang and screw through the third groove in from the outside edge of the deck board. This will ensure the board is firmly secured to the decking frame.
For the rest of the boards, always screw into the second groove from each side and fix to the frame with 64mm decking screws. Repeat this at the opposite end of the board, as this will ensure the board remains straight, and then work down the board, fixing the screws into each joist below.
To ensure you maintain a gap of between 5mm and 8mm between each deck board, create a suitably sized spacer from an offcut of timber and use it to check that the gap between boards is equal all the way along.
If you need to cut a deck board to accommodate an obstacle, create a template and mark the saw guideline onto the wood, then cut with a jigsaw.
Adding fascia boards
Mark the fascia board with a line at 50mm from each end. Then, from the first 50mm line, measure out and mark lines at 600mm intervals down the length of the board.
Put the fascia into position and place small offcuts of wood or packers underneath the fascia to level it. Using the lines you drew as a guide, pre drill guide holes into the second groove in from each side. Secure with 64mm decking screws.
Finally, if you’d like to add lighting or railings to your decking, you can follow our step by step ‘How to assemble deck railings’ or ‘How to install deck lighting’ guides.