Decking over patio

17 Apr 2006
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United Kingdom
Hi there

Having had two builders unwilling or too lazy to quote on the project we have decided to deck an area immediately outside the back door measuring roughly 7m x 3m ourselves.
At present this is an old, but stable patio however it has seen better days and we would like to replace/cover. Both builders who visited said it would be possible to build a frame immediately on the patio and then deck on top of the frame.
The fact that this is apparently feasible makes a DIY job seems reasonably straightforward, however I have a few questions and was wondering if others had done the same job could office some advice.

1. Firstly and most importantly, is it feasible to construct the timber frame directly onto the existing patio? If so I assume that I need to avoid the frame directly resting on the patio slabs, what do I use to overcome this?

2. To avoid drilling into the house and also to avoid any damp issues I intend to leave a gap of a few cms between the exterior wall and the deck, this means that I to anchor the deck frame to the patio. As with question 1, is this possible and what should I use?

3. I am quite happy to build the frames once I know how I should secure to the patio, however the dimensions are my next worry. Surely 7 metres is too long for a frame length, and also 7m is beyond the typical length of a decking board. Does this mean that I need to construct smaller frames and then screw together? Also to avoid having to join lengths of decking, should I design so the decking runs in the opposite direction, i.e. to a maximum length of 3 metres?

Any advice/experiences of similar projects?
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yes it can go over the patio.

yes it can bear on the slabs.

it isnt a damp issue and the frame can be fixed to the wall.

decking will look better if you can do it with single boards rather than joined ones. Just build the frame up in sections to deal with this.

if you look down the forum ive answered very similar questions in lots of detail, which should give you more help.
Thanks Thermo

I can't find the post you mention, how old would it be?

Anyway you mention building frames, would you suggest that we build two large sections (what typically works well size wise?) and run the boards to their full length.

Once we have what is the nicest and cleanest way to join?
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secure a run of timber to the wall with rawlbolts. build the outside of the frame off of that. then infill with the cross memebers to make up the frame. Its a lot easier then building the frames and then putting them in place, as no houses/walls etc are ever square.

have a look down the next few pages there have been plenty of questions about decking in similar situations that ive done lengthier explanations on. im not being rude, im just a bit pushed for time at the moment!

In regards the last question what are you referring too?
Sorry the last question was how we should join the 'frames' together and where. If the width of the deck is 7 metres this will be too long for the decking boards ( I think).

Hence how once the frame is built over the whole patio area should we join the frames together to neatly match?


Firstly, boards usually look better if they run away from the house. In your case is that the shorter dimension? I suspect it is. Consider doing that and you'll have a better-looking deck (in my opinion). Deck boards can come in lengths up to 4.8m or so if you avoid the likes of B&Q.

Secondly, frame sections should be bolted together.

If you do need to join two deck boards together, ensure the following:

Check the board ends are square - don't assume they are just because they've been cut by the supplier.

Stagger the joins, so you don't have all the joins in a continuous line. I use three different join points, staggering them alternately.

Where boards join, make sure you have two frame joists so each end of the boards have a joist to sit on.

I have seen boards joined by cutting each at 45 degrees. Debatable if that looks better. Your choice.
Yes you are correct in that the shorter distance is that 'running away' from the house, that's also the direction of the fall and hence I suspect is the option we should choose on two counts, i.e it means that we won't have to join boards at all.

One other thing that is worrying me is the final cut of the boards.

I think we can build the frame without too much fuss but in the book I have seen the illustrations suggest that the last step is to cut the boards to a uniform length once they are fitted.

Isn't that a risky strategy, having not used a circular saw before would I better off cutting each one in turn before fitting in case I mess up the whole job?
possibly, if you don't mind measuring each and every board before cutting. Best way is to let them overhang, then run the circ saw along a straight edge. Whatever you are most comfy with really.

How are you going to leave the cut ends? All cut ends should be treated with end-grain or cut-end preserving fluid (cant recall the actual name - get it in B&Q etc) as the pressure treatment does not go in to the wood very far. Also, you can put a trimming board horizontally along the front egde to hide the cut ends. I use tyhe back side of a board ie the smooth side. Looks best. Have fun!
This is really fantastic feedback, getting more confidence with each post!

Two final questions I think.

1. Is it ok to use 4 x 2 to form the frame against the exterior wall?

2. Can the frame (made from the 4 x 2) come into direct contact with the patio? Should there not be some support or protection?


as long as it's pressure treated I don't see why not..

if it worries you you can always get some galv plates or washers to nail into the underside every meter or so to keep the suports off the floor..
lisach said:
This is really fantastic feedback, getting more confidence with each post!

Two final questions I think.

1. Is it ok to use 4 x 2 to form the frame against the exterior wall?

2. Can the frame (made from the 4 x 2) come into direct contact with the patio? Should there not be some support or protection?
Its unlikely that the patio was laid true enough to use as a direct support for the frame. Better to prop it up on posts as legs part way along each frame section (only needs to be a few mm off the ground)


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