Custom Trapezoidal Outdoor Cover | Waterproof - Stepped / Pitched Top (Made to Measure)
Made-to-measure cover for stepped / pitched-top boxes (Design 11)
Not all outdoor boxes and housings are simple rectangles. Design 11 is for anything with a stepped or pitched top – where the height at the front and back is different and there is a small flat section across the top. Think of pump housings, storage boxes, filter covers, small plant or equipment enclosures and awkward utility boxes that never fit a standard cover.
This custom cover is sewn to your exact measurements using our waterproof, UV-resistant outdoor fabrics, with optional tie-down systems to keep everything secure in windy UK weather.
What Design 11 is ideal for
- Stepped or pitched-top storage boxes and utility housings
- Small pump, filter or equipment boxes with sloping fronts
- Custom-made garden built-ins and bespoke joinery
- Any box where the front and rear height differ and you want a neat, shaped fit
How Design 11 is measured
Simply follow the numbered diagram image (ALT set to “diagram” or “size”):
- Front height – from ground to the highest point at the stepped front edge.
- Base depth – along the ground from front edge to back edge.
- Top length – across the top from left to right.
- Rear height – vertical height at the back corner.
- Top flat depth – the shallow flat panel running across the top.
Always measure in centimetres, at the widest and highest points you want to cover. We build in a small tailoring allowance so the cover slides on easily without being baggy.
Fabric options – choose the right tier for your job
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Tier 1 – PVL 600D
Tough vinyl-coated polyester that’s fully waterproof and great value for everyday garden use. Ideal for storage boxes in typical UK weather. -
Tier 2 – P500UV
Premium 500D polyester with PU + UV coating for maximum water-resistance and long-term sun protection. Best for very exposed or coastal locations, or when you’re protecting high-value equipment.
Both fabrics are designed specifically for outdoor covers, with robust stitching and careful pattern cutting to suit this more complex Design 11 shape.
Tie-down options to suit your location
- No tie-downs – simple drop-over cover for sheltered corners or heavy boxes.
- Elasticated hem with cord lock – shock cord around the base to cinch the cover tight.
- Grommets & cord – reinforced eyelets so you can tie the cover to posts, brackets or anchors.
- Straps & buckles – webbing straps under key points for maximum security in exposed areas.
Why order your Design 11 cover from Shiny Sofas?
- Custom sewn to your exact measurements – no more baggy or oversized generic covers.
- Waterproof & UV-resistant fabrics chosen specifically for outdoor use.
- Neat, shaped fit that follows the stepped / pitched top profile.
- Optional tie-down systems to match your wind exposure and installation.
- UK-based support – send us a photo and we’ll happily double-check your measurements.
Need help or something even more complex?
If your box or housing is slightly different to the diagram, don’t worry. Upload a clear photo, add notes in the box at checkout, or contact us before ordering. We can often tweak the pattern, add cut-outs or zips, or recommend another custom cover design that will suit your project better.
💳 Pricing & Payment Information
The price shown above is an instant estimate based on the measurements, fabric and options you select.
At checkout, a standard base price may be displayed — this is normal and is used to place the order.
✔️ Your final price is calculated from your measurements, as shown in the price estimate on this page.
✔️ Any difference is confirmed before production begins.
✔️ If an adjustment is required, we will contact you or issue an updated invoice before sewing starts.
By placing your order, you confirm your measurements and acknowledge that custom-made items are priced according to size and specification, not the base product price.
How the tie-down options work
Choose the tie-down style that best suits your garden and wind exposure. All options are sewn to order on your cover.
- No tie-downs – simple drop-over cover, ideal for sheltered areas.
- Elasticated hem + cord lock – shock cord sewn into the base with a toggle to cinch tight.
- Grommets + cord – reinforced metal eyelets around the base with cord to tie to posts or anchors.
- Straps & buckles – webbing straps run under key points of the base for maximum security.
You can see close-up photos of each option above in the product gallery.
Questions about this custom Design 11 cover?
Send us your question using the form below and we’ll reply by email. We’ll also add common questions and answers here to help other customers.
Frequently asked questions
What is Design 11 best for?
Design 11 is ideal for boxes and housings with a stepped or pitched top where the height at the front and back are different and there is a small flat section across the top. If your item is a simple rectangle, a standard rectangular cover will usually be better.
Are the fabrics fully waterproof?
Both fabric tiers are designed for outdoor use. Tier 1 (PVL 600D) is waterproof for everyday garden use, while Tier 2 (P500UV) adds an extra PU and UV coating for maximum water resistance and long-term exposure.
What if my measurements are slightly wrong?
We add a small tailoring allowance to help the cover slip on easily. If you realise you’ve measured incorrectly, contact us as soon as possible with your order number – if production hasn’t started, we can usually update the sizes.
Can you add cut-outs or zips?
In many cases we can add simple cut-outs, flaps, vents or access zips. Upload a clear photo and describe what you need in the notes – we’ll confirm what’s possible and whether there is any extra cost before we sew your cover.
How do I clean the cover?
Brush off loose dirt regularly, then sponge clean with mild soapy water and rinse. Avoid harsh chemicals or machine washing, as these can damage the waterproof coatings over time. Always allow the cover to dry fully before storing.
Popular sizes & example prices
These examples use our live pricing calculator and show what typical Design 11 covers cost with both fabric tiers. Enter your own measurements above for an exact price.
Prices shown include fabric cost and our minimum order charge where applicable, based on a simple drop-over cover with no tie-down upgrade.