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Timber Decking - How to Lay Timber Decking

supplied by Wickes.co.uk ©2008 All rights reserved.

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The component parts of the Wickes decking and pergola system are shown in the Project List at the bottom of this page, and in this leaflet you will find a variety of ways in which they can be used. Provided that certain rules are followed our examples can be adapted to suit your needs.

Main features of the softwood timber components are:

• Pre-treated for excellent resistance to rot and insect attack.
• Fluted deck boards to help reduce slip and aid rainwater drain-off.
• Decks and / or pergolas can be connected to a building or free standing.
• Pergola components can be used to make archways or walkways.
• Decks can be built off sloping ground.

With the components parts illustrated in FIG. 1 you can construct a number of garden features ranging from basic square or rectangular decks to decks on different levels with or without pergolas being added. In the remainder of this leaflet you will find a variety of options along with shopping lists and cutting and construction details. For basic deck building only basic carpentry skills are required. More advanced projects do require greater planning and carpentry skills, but your level of skill will almost certainly improve as each project is completed.

Decking timbers, like any natural timber, can expand and contract depending upon ambient conditions. When you put them outside they may swell or, if the weather is very hot and dry, they will shrink. It is therefore advisable to purchase your timbers a week or so before you plan to construct your deck to allow the boards to adjust to the atmosphere. Store them close to where they will be used and ideally cover. Store them on level ground on timber bearers.

All decking components are treated with a preservative treatment, however, when any of these are cut the cut surface must be treated with Wickes Decking Preserver to maintain the integrity of the treatment. Follow the instructions on the can, failure to treat correctly could affect your guarantee.

 

Safety

Take normal safety precautions when working with timber products. Wear gloves to avoid splinters and a nose and mouth mask when cutting to avoid the inhalation of dust. Always wear goggles when using circular saws, drills or sanders and always use an RCD device when using any power tools outside.

You will collect timber offcuts which, if not used as deck strengtheners, may be stored for later use. Do not burn them and certainly do not use them as fuel for a barbecue. Remember that they are preservative treated.

 

Deck Planning

It is essential to plan your deck in advance and this is best done on paper. You cannot simply make up a bearer frame of any size and then expect the deck boards to fit with the required gaps between them without having to reduce the width of boards to fit.

Carefully decide on the location and the use of your deck. Decide on whether you want a sunny or shaded location and importantly whether privacy is a requirement. Decks in permanent shade could be affected by damp and consequent algae growth. Listen to the views of your family and ensure that any decking feature is not too big for your garden. Be aware that very large decks and raised decks may require planning permission. Raised Decks should not be built with the deck level more than 600mm above ground level without specialist advice. When installing posts or levelling take special care not to damaged underground pipes or drainage and do not obstruct manhole covers or other services.

FIG. 2 shows a basic deck using boards and 80 x 80mm bearers with an overall size of 3040 x 2400mm. The layout of the bearers is shown and a shopping list is included. In this example the width of the deck is based upon the use of 21 uncut 2.4m long and 140mm wide deck boards with 20 gaps of 5mm between them. The calculation is: -

21 x 140 = 2940
20 x 5 = 100
Total width = 3040mm

The base is designed to provide a complete perimeter with intermediate bearers at no more than 500mm spacings. The bearers are cut to length to suit the dimensions. FIG. 2 also shows how deck boards can be laid in a variety of ways. It is important that you plan your layout before assembling your bearers as the pattern will affect the spacing and number of bearers, e.g. double bearers will be needed for some chevron styles. See FIG. 3.

Plan your deck bearing in mind that it is the deck boarding that basically governs the size. For any deck you will need to work on the board widths at 140mm plus 5mm gaps in between.

As a quick guide:

10 boards and 9 gaps = 1445mm deck width
12 boards and 11 gaps = 1735mm deck width
14 boards and 13 gaps = 2025mm deck width
16 boards and 15 gaps = 2315mm deck width*
18 boards and 17 gaps = 2605mm deck width
20 boards and 19 gaps = 2895mm deck width

*This is the key deck square, which has been sized to allow the other modules to interlink creating numerous deck designs.

Designing such a deck to limit cutting and board or bearer wastage is difficult but not impossible. The art lies in constructing separate modules which link together in a number of ways. By using up to five different modules designed by Wickes a whole variety of deck designs and sizes can be built.

If the site is sloping and it is not possible to level the ground you can still install a deck but part of it will have to be supported on timbers set into concrete in holes in the ground. A completely raised deck can also be installed using the same method but the deck level must not be more than 600mm above ground level. Do not build decks in very wet areas as constant contact with water could effect the life of the timber.

FIG. 4 shows a number of deck designs using a combination of several modules with boards running in different directions for added interest. In all cases the bearer modules have been built as separate items and then connected in situ and then boarded out.

FIG. 5 shows the construction of each module and lists the material requirements.

Using FIG. 5 you can draw out your own design and calculate your own material requirements.

 

Site Preparation

Mark out the deck area using pegs and a string line following your plan drawing. If the ground is slightly uneven, level it off and make sure that it is firm.

If laying the deck over grassed or weedy areas we recommend that turfs are removed then Wickes Landscaping Fabric is laid over the area to prevent future growth under the deck. If the ground is soggy or likely to become so in wet periods spread pea shingle over it to a depth of about 25mm. Your bearer frame will bed down onto the shingle and will, to a large extent, be kept off almost permanently wet ground.

If you are constructing a deck on level ground further marking out is not normally required as bearers can be laid out in the positions that they will be used.

 

Basic Bearer Frame Assembly with 80 x 80mm Bearers

Make the outer frame first, then mark, cut and fit the intermediate bearers remembering the maximum 500mm spacing limit. Treat every cut end with Wickes Decking Preserver. At each join use two 150mm exterior nails. As you proceed make sure that the frame remains flat and square. To check the squareness measure the frame diagonals. They must be equal.

Make sure that the frame rests flat and is totally supported. If you find hollows under the frame or areas where it is held off the ground you may need to adjust the ground level to prevent the deck being 'springy'.

If longer bearers are required these can be joined together by skew nailing offcuts, see FIG. 6.

The laying of a modular deck is essentially the same as for the basic deck. The only real difference is that each modular frame will be put in place, the next one added alongside and the two connected with 150mm exterior nails through the bearers at no more than 300mm centres. These nails should be driven in at an angle - skew nailed - as in FIG. 7 to make it more difficult for the timbers to pull apart.

If the site is on a slight slope and it is not possible to level the ground you can still install a deck but part of it will have to be supported on timbers set into concrete in holes in the ground. See FIG. 8.

 

Fixing Softwood Deck Boards

The deck boards are fitted and secured to the bearers using No.8 x 65mm Exterior Woodscrews, two screws per board to each and every bearer. The screws should be located about 15mm in from the edge of each board and in a hollow. FIG. 9.

Decking Boards can either be cut to the size of the frame or you can fit them over sized and trim down later. See FIG. 10.

Decks do not have to have hard straight edges. Curves can be created provided that the unsupported decking is not more than 150mm away from a bearer. Curves can be marked out with either a string line in an arc or with a piece of timber fixed to create an arc. See FIG. 11.

NOTE: Due to the timber width variations mentioned earlier you should not stick rigidly to fixing the first board, measuring or using a 5mm spacer then fixing the next board and so on. It is better to loose lay boards initially to determine what the gaps will actually need to be.

The edge timber can be used to create the appearance of framing the deck boards. It is glued, nailed or screwed in position as required. The deck boards are cut to size and shape, then fitted as previously described. The sequence for fitting the edging timber can vary depending on the design of your deck. It can be fitted prior to the deck boards, which are then cut to fit, or one side is boarded first, then edged, and then the other side is boarded. See FIG. 3.

You may wish to use the deck boards to edge around the perimeter of your deck, covering up the bearer frame wood. See FIG. 12.

 

Raised Decks

 

Building a Frame Assembly for a Raised Deck

The frame or frames are constructed using 47 x 150mm stress graded joists and 100mm exterior grade nails to join the timbers together. One of the most difficult jobs when building a raised deck is the setting out of the posts. The easiest way of doing this is to make up the frame first and then use temporary legs to support it. When the frame is in the correct position and you have checked that it is level, dig out the holes for the posts. These are positioned in the corners of the frame and at a maximum of 1200mm centres. Most post holes will need to be 700mm deep depending on soil types. Use half a medium density block at the base and position the post ensuring that it is truly vertical. See FIG. 8. Secure the post to the frame with coach bolts or screws and pour in Postcrete or a concrete mix. Remove the temporary legs once this has cured.

The intermediate joists should be set with maximum centres of 400mm. Depending on the size of the deck intermediate post supports may also be required on the intermediate joists this will reduce any movement on the deck surface. See FIG. 13

 

Installing Steps

Using a pair of pre-made step risers is the simple way to add steps to your deck. Steps wider than 500mm will require additional support timbers.

With the width decided, cut two lengths of deck board to fit between the two risers and secure these with 150mm nails. See FIG. 14. Once these have been fixed the risers can be attached to the deck frame with No.8 x 65mm Exterior Woodscrews. Deck boards can then be fitted and if required you can fit cut deck boards at the back of the step. Handrails can be fitted as in FIG. 15.

 

Fitting Spindles and Handrails

For safety handrails and spindles should always be fitted to raised decks to prevent anyone accidentally stepping off the side. Newel posts need to be notched out and are then fixed to the bearer frame with Exterior Coach bolts. See FIG. 16.

Handrails are fixed to the newel posts with Exterior Wood screws. Square spindles are fixed to the bearers and handrail with 65mm x No.8 Exterior Woodscrews. It is important to note that the spindle spacing should be such that a 100mm sphere cannot be passed through the gaps.

The shaped spindles are fitted in a slightly different way. A hand rail is used as the base rail and the spindle, base and handrail are assembled before positioning them between newel posts. No.8 x 65mm screws are driven through the base rail into the centre of the spindles and skew screwed at the top into the handrail. See FIG. 17.

Pergolas

Plan your pergola on your deck layout first. The same pergola components can be used to build a free-standing feature or build a canopy off the house wall.

FIG. 18 shows the positioning of pergola posts in relation to the deck. Note that corner posts are located slightly differently to intermediate posts but all have a housing cut out to enable the posts to overlap the deck by 21mm wherever balustrading is to be added. This diagram shows connection and positioning details. For stability the posts should not be cut off at deck base level but should be concreted into holes dug in the ground adjacent to the deck, or firmly secured to the deck frame posts. When constructing a pergola on a raised deck you must ensure that the pergola uprights are firmly attached to the deck frame which may require the use of additional timbers. With rigid posts the risk of a pergola structure 'racking' sideways is eliminated. All posts must be set vertically.

The overlap is essential if balustrading is to be used because handrails are connected to the posts in some cases and to newel posts in others, so alignment is necessary. The 21mm cut-out is duplicated on the newel posts, whilst the square spindles are fitted directly to the outside face of the deck bearers. This can be seen in FIG. 18, which illustrates balustrading - newel posts and spindle location and fixings.

It is important to note that the spindle spacing should be such that a 100mm sphere cannot be passed through the gaps.

FIG. 19 illustrates methods of constructing the pergola top.

If your pergola requires a vertical support part of the way across a deck you should locate this support before any others which have to be in line with it. Remove deck boards to locate a frame bearer. Secure the posts to the bearer using two 160mm exterior coach bolts. It must also extend into a hole in the ground as described earlier and be concreted in place. The deck boarding must then have a section removed to fit around the post.

 

Staining & Aftercare

When you have completed the construction of your deck it is very important that the surfaces are treated with either Decking & Garden Furniture Preserver or Stain & Preserver. Pay particular attention to any end grains and smaller products such as finials and spindles. Coat all sides of the deck and these should be re-applied every year to keep your deck in the best condition.

Any cut timbers must be re-treated with Decking Preservative which are available is six types, three wood effects, Oak, Chestnut and Redwood. Two colours, Green, Dark Brown and clear. There is also a Decking Seal, which is clear and a Patio & Decking Cleaner to remove any growth of moss or algae from the boards.

Wickes Decorative Wood Preserver, Wickes Decking and Garden Furniture Clear Preserver and Wickes Decking and Garden Furniture Woodstain Preserver contain Dichofluanid and Propiconazole. Read the label before you buy and USE PESTICIDES SAFELY.

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