DIYdeals - Instructions for Raised Timber Decking

(with or without Pergola) E-mail any questions to timber@diydeals.com

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1.  For all Raised Patio Decks 2.4, 3.0 & 3.6m wide x 2.5, 3.1 & 3.7m with or without Pergola or Balustrade

Before starting erection of Deck

Please note that deck-boards and joists are the same grooved timber. The deck-boards may be used grooved side upwards, plain side upwards or alternated 1 up & 1 down for a variation - depending on your choice. The grooved side will help prevent slipping in wet conditions.     

A. Marking out position of deck

i. Choose a site where the front to the deck will have the lowest step-up.  The site can slope downwards up to 600 mm.  Balustrade should be used on falls of over 300mm.  Mark out the perimeter with pegs and line.  Check for squareness by measuring for equal diagonals.  Clear any obstructions that may interfere with the deck or pergola - ground levelling is not required as the posts will be used to level the deck.

ii. Mark out where the Metal Post Anchors will be positioned - when in place they will have their bolts facing to the front and their outside edges will be 2.0m apart - both ways and distances to outside should be equal . Check for squareness of the post anchors by measuring for equal diagonals.

B. Driving Post Anchors into the ground, cutting and fixing Posts

i. Cut a piece of post to use inside the Post Anchors when driving them into the ground. With the Bolts facing the front drive the Anchors into the ground continually checking and adjusting for uprightness and squareness.  Place Support Joist (E) upright against the Post Anchors (A & B) raised off the ground approx. 30 mm at the front (use a  board laid flat) - level the joist and temporarily support at the back.  Repeat for Support Joist  (H).

ii. If No Pergola is required cut the 2.1m. post so that there will be 4 short posts each coming in line with the top of the Support Joists from the base of the Post Anchor. Make cuts with a slight fall from front to back.

iii. If using Pergola measure the approx. height you wish the top of the Pergola Support to be, say between 2,000 mm & 2,300 mm depending on your preference from the top of the joists.  Calculate the Post length for all Posts from the base of the Post Anchor.  Make cuts with a slight fall from front to back.  For both, keep the off-cuts from the posts for use as noggins (Q) Brush Preserver onto the cut surfaces of the Posts

iv. Fix Posts into Post Anchors  (where possible, ensure cut edge is at the top with the fall from front to back to assist clearing rainwater). Posts may require easing to fit the Post Anchors -Brush Preserver onto the cut surfaces -Check verticals & tighten bolts to ensure good grip. It is advisable to concrete in the Post Anchors after fixing all the joists and pergola timbers. 

2. Fixing the Pergola

i. Shaping Pergola timbers and Fixing the pergola supports & tops - Pergola timbers may be left square or a 50 mm cut at 45 degrees may be made, if desired.  Brush Preserver onto the cut surfaces.

ii. Position Front Pergola Support against and to line up with the top of the Posts (A & D) and to line up with Side Joists (L & M) - this should give equal overhang from the Posts.  Temporarily fix with one large screw.   Check levels and adjust if necessary.  When happy with the height and level - fix with 3 more screws into each post to secure.  Repeat for Back Pergola Support at front of Posts (B & C).  Check uprights and place both outside pergola tops so that there are equal projections. Position the 2 outside tops 250 mm from ends and space remaining tops at equal centres.  Screw in place with a large screw from both sides of  the top into the Pergola Support. There are 5 pergola tops for 2.4m wide, 6 for the 3.0m wide and 8 for the 3.6m wide decks.

3. Fixing Support Joists E, F, G, & H to Posts A, B, C & D

A. Select the 4 strongest joists with the fewest and smallest knots for use as Support Joists.

i. Ensure that the first Support Joists (E & F) will be fixed to Post (A) which will be the post on the highest ground. (i.e. the one where the Support Joist will be nearest the ground and preferably the front entrance to the Deck).  Place the Support Joist (E) on the outside and Support Joist (F) on the inside of the Posts (A & B) - so that there is an equal projection from Posts (A & B)_.   Position Support Joists (E & F) against Post (A) approx. 30 mm off the ground at the front and use the Drill Bit provided to make a hole all the way through the joists, the metal socket and the post - drill the hole 40 mm from the bottom of the Support Joist and 10 mm offset from the centre of the post.  Do not drill the second hole into the same post yet because it is necessary to create the levels with all the other Posts and Support Joists first.  Temporarily fix both Joists to the Post with a Bolt.

ii. Checking that the level of Support Joists (E & F) are correct, position them against Post (B) and drill, as (2Ai). You may not be drilling through the metal of the Post Sockets if there is a slope.  Using one of the other timbers as a straight edge align & level Support Joists (G & H) with Support Joists (E & F) and position against Post (C) matching projections and drilling as (2Ai).   Checking that the levels of Support Joists (G & H) are correct, position them against Post (D) and drill as (2Ai).  Check that the joists attached to Post (A & B) are level with those attached to Post (C & D) Adjust if necessary.

B. Drilling a second hole in each post, Fixing the Washers and tightening the Bolts

i. When all Support Joists are level - Drill a second hole 40 mm from the top of the Support Joists and 10 mm offset the other way from the centre of each post.  Do this for Posts A to D.  You may not be drilling through the metal of the Post Sockets for these upper holes - if you have this situation -   Mark the Posts at the top of the Joists. Remove all Bolts and the Support Joists from their temporary fixings.  Keep by the Posts. Position Washers where necessary, in between the Posts and the Support Joists to compensate for the gaps created by the Post Anchors, push all 8 Bolts through the Support Joists, Posts and Post Sockets using a washer against the joist at the back before tightening the nut - ensuring the washers have sunk a little into the joists.

C. Fixing Post Noggins between Support Joists (Q)

i. Cut the post off-cuts into 6 No. approx. 75 mm  cubes and position 4 of them 150 mm from Joists (J & K) between and in line with the bottom of the Support Joists (these 4 are not required for the 2.4m joists) - fix using 2 large screws into both sides. Brush Preserver onto the cut surfaces.  Leaving a gap of at least 50 mm from the top of the Support Joists ensures the deck boards clips will not snag.  Position the other 2 in the centre between and in line with the bottom of the Support Joists - fix as above. Post Noggins are used to prevent distortion on the Support Joists and should not be left out.

4. Fixing Outer & Centre Joists

A. Hanging Front & Rear Joist (J) from Support Joists (E, F, G & H)

i. Position Front Joist (J) against Support Joists (E & F) and ensure equal projections from both outside Support Joists.   Place 4 Hangers so that they rest on top of  Support Joists (E, F, G &H) i.e. open end pointing downwards with the back against Front Joist (J) and when correctly aligned - flush with the top of the Support Joists and with equal projections - mark the positions on Front Joist (J) where the 6 screws in each Hanger will be fixed.  Remove and fix the hangers to Front Joist (J) using the Small Screws. To give maximum strength the screws will be a tight fit and may need ‘starting’ with a tap from a hammer. Place Front Joist (J) over Support Joists (E, F, G & H) so that it rests on the Hangers - secure to Support Joists by screwing into the timber on one side.

B. Fixing the Side Joists (L & M) to Front & Rear Joists (J & K) and Hanging the Centre Joists (N & P)  

i .Lay the Side Joists on the ground with the inside face pointing upwards.  Position the longer side of the Corner Brackets on the Side Joists so that they are flush with the end and are 20 mm in from the top & bottom.  Use 3 of the Screws to fix each Corner Bracket to the Side Joists.  Ensure that the tops of all Joists are flush and fix the Side Joists, using Small Screws, into each end of the Front & Rear Joists (J & K) ) - this can be flush (especially when joining two decks together) or, if desired, up to 40mm in from each end to provide an overhang for the deck boards.

ii. Mark the centre of the Front & Rear Joists approx. 800 mm in from the Support Joists.  Position the remaining 2 Hangers at the bottom of the Front & Rear Joists centrally across each of the 2 marks with the open end pointing upwards, so that the Centre Joist (N) will later rest on the Hangers.  Fix the Hangers with the 6 Small Screws onto the Front & Rear Joists.  Drop the Centre Joist into place - and secure by screwing into the timber on one side.

C. Before fixing Balustrade and/ or Deck Boards concrete around post sockets.  Dig out approx. 300 mm deep and 400 mm square around each post socket, recheck they are upright & square with plumb rule or level and fill with concrete to prevent movement

5. If using Balustrade - click here

6. Fixing the Deck Boards (if using a balustrade fix the newel posts before fixing deck boards)

A. Attaching Deck Board Ties to the Deck Boards.

i. Stand all but one of the Deck Boards on edge and fix 5 Deck Board Fixing Clips to each so that they are spaced: one in the centre, one (500mm for 2.4m, 600mm for 3.0m or 700 mm for 3.6m wide deck) either side of the centre and one 200 mm from both ends.  Fit them so that the tongues line up with the bottom edge - use the Short Nails and hammer firmly into place.

B.  Fixing the First Deck Board

i. This is the only one without Deck Board Fixing Clips attached.  Position the first board - it should have an overhang of no more than 20mm or be flush with the front of the Front Joist.  Check that it lines up with the ends of the front joists if using a overhang over the side joists.  Drill a series of eight 3 mm pilot holes at an angle through the top corner of the front edge of the First Deck Board in line with all 8 Joists and screw through each a Long Screw into the Front Joist checking that this first Deck Board is flush with the front and ends & square. Tighten screws so that the screw head goes just below the surface. Repeat the fixing onto the back edge of this first Deck Board with 1 long screw into each joist so that the back screws are hidden when the next Deck Board is fixed.

C. How to calculate the gaps between the Deck Boards

i. Because the Deck Boards can vary in width by approx. 3 mm depending on the moisture content it is better when spacing to measure from the front edge of the board already in place to front edge of the Deck Board being placed.  Remember that the Boards will increase in Winter and reduce in Summer.  The recommended Front Edge to Front Edge spacing is 147/ 148 mm.  Fixing the Boards too close together in the Summer Months may cause them to buckle up in Winter.

D. Fixing the 2nd and subsequent Deck Boards

i. Place into position by tucking the tongues under the board in front checking that it lines up with Side Joists (L & M).  Leave the required gap then screw with 8 long screws - one into each joist. Pre-drilling especially over the Side Joists will reduce splitting.  Continue with the subsequent boards until reaching the Posts (if using Pergola) - if with no pergola proceed to (6F)

E. Cutting & Fixing Deck Boards around the Posts when using pergola

i. The spacing should work out that two boards will need cutting around each set of Posts.

ii. Place the first of the Deck Boards to be cut up against the Posts from the front and line up with Side Joists (L & M).  Mark with a pencil where the posts will go and also mark the depth to line up with the back of the posts - mark the area to be cut out. (It is better to make the cut-out a little bigger than smaller).  Use a hand saw or preferably a jigsaw to cut along marks - allow 3 - 5 mm for clearance around Posts. Carefully chisel out the block where post will go (by removing more from the underside it will be easier to fix into place against the Post.   Temporarily check to see if the cut-outs fit and that the outside edges are in line with the Side Joists (L & M) - make adjustments if necessary.  Brush Wood Preserver onto the cut surfaces.  Fix as above, pre-drilling the Deck Boards above the Support Joists, by the cut ends, is recommended to avoid splitting.

iii. Place the second of the Deck Boards to be cut up against the Posts from the back and line up with Side Joists (L & M). Cut & Fix as in (6Eii)

F. Fixing the last Deck Boards

i .When placing the boards after the back posts, check to see what gaps are required between deck boards and if adjustments are necessary.  It does not matter if there is an overhang of up to 40 mm, but screwing through the face will be necessary to fix the last board. If the Last Board lines up with the Rear Joists -Fix as  (6Di).

7. Finishing & Maintenance

i. All timbers being Preserved further treatment is not necessary and the timber will fade to a natural grey colour.  If preferred, the deck may be coated with Decking Stain to the colour of your choice. If there is any build of moss, after winter use an anti-fungicidal and hose down to remove.  To restore the colour apply a further coat of Decking Stain.

ii. Dispose of all waste timber in your dustbin - do not burn.  Wash hands after handling timber - especially before eating.  Always wear safety glasses when using power tools.

Help Line -

For more information - contact Peter Dale on 01457 855259

All rights reserved.  04/01/2008.

You may print this copy for use during erection.  This leaflet may not be reproduced in whole or in part without the prior written approval of Peter Dale.

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