I've got a new shed being put up this weekend, I want to try to seal it up to keep some of the bugs from taking over. After looking around Focus DIY (large DIY chain in the UK) I found some "wood sealer", which comes in a tube and slots into a gun for squeezing out.

Each tube costs £6 and I think I'd need about 20 or so in order to seal a 6' by 8' shed, is there a cheaper or more effective method?

  • just to be clear, you mean seal as in Wood Sealant and not as in sealing up a crack via caulk or expandable foam - correct? Oct 31, 2010 at 17:23
  • I don't want to seal cracks in the wood itself, but the gaps between each plank of wood.
    – user155695
    Oct 31, 2010 at 18:02
  • how wide are the planks?
    – SqlACID
    Nov 1, 2010 at 1:23
  • I would say that the main thing you want to keep out of your shed isn't insects but rats. Roaches in a shed I can live with. Rats, no way. I am building a fire wood store shed this weekend and I either need to lay down some ply on top of the cheap wooden decking floor or leave no gaps whatsoever. Faster to put some ply down on top.
    – Benjamin R
    Jul 23, 2015 at 4:20

4 Answers 4


Just lay some tongue-and-groove OSB plywood on top of the planks.

For a 6x8 shed, you should only need two 4x8 sheets - which should certainly cost a lot less than the £120 you would pay for sealer.

Or for that matter, just have them use T&G plywood for the flooring in the first place.

  • You don't even need T&G. Just any thick plywood will do the job.
    – Benjamin R
    Jul 23, 2015 at 4:17

Because a shed is generally subjected to temperature extremes you need to consider that its floor is prone to expansion and contraction. You therefore need to allow for some movement and whatever you use to fill the gaps needs to remain at least slightly flexible. Something I haven't tied myself but think might work is the dense foam rubber strips that are used in some places for expansion joints in concrete, if your gaps are large enough to accommodate them. Failing that I'd suggest a caulk that develops a semi-hard skin.

  • Rats and mice will eat through that rubber with no difficulty.
    – Benjamin R
    Jul 23, 2015 at 4:21

You can seal any gaps with expanding foam spray. Just be sure to wear disposable gloves while applying.


I tried foam spray to fill gaps in my kitchen cabinet under the sink. It kept out the mice but looked bumpy and messy.

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